The development of effective bifunctional catalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is significant for energy conversion systems, such as Li–air batteries, fuel cells, and water splitting technologies. Herein, a Chlorella-derived catalyst with a nestlike framework, composed of bamboolike nanotubes that encapsulate cobalt nanoparticles, has been prepared through a facile pyrolysis process. It achieves perfect bifunctional catalysis both in ORR and OER on a single catalyst. For our optimal catalyst Co/M-Chlorella-900, its ORR half-wave potential is positively shifted by 40 mV compared to that of a commercial Pt/C catalyst, and the overpotential at 10 mA cm–2 for the OER is 23 mV lower than that of a commercial IrO2/C catalyst in an alkaline medium. This superior bifunctional catalytic performance is benefited from the simultaneous increase of pyridinic N sites for ORR and graphitic N sites for OER. In addition, N-doped carbon-encapsulated Co nanoparticles improve both ORR and OER performance by forming new active centers. The unique nestlike carbon nanotube framework not only afforded highly dense ORR and OER active sites but also promoted the electron and mass transfer. Our catalyst also displays notable durability during the ORR and OER, making it promising for use in ORR/OER-related energy conversion systems.Keywords: activity sites; biomass; nitrogen-doped carbon nanotubes; oxygen evolution reaction; oxygen reduction reaction;

A class of core–shell structured low-platinum catalysts with well-dispersed inexpensive titanium copper nitride nanoparticles as cores and atomic platinum layers as shells exhibiting high activity and stability for the oxygen reduction reaction is successfully developed. Using nitrided carbon nanotubes (NCNTs) as the support greatly improved the morphology and dispersion of the nitride nanoparticles, resulting in significant enhancement of the performance of the catalyst. The optimized catalyst, Ti0.9Cu0.1N@Pt/NCNTs, has a Pt mass activity 5 times higher than that of commercial Pt/C, comparable to that of core–shell catalysts with precious metal nanoparticles as the core, and much higher than that the latter if we take into account the mass activity of all platinum group metals. Furthermore, only a minimal loss of activity can be observed after 10000 potential cycles, demonstrating the catalyst’s high stability. Atomic-scale elemental mapping confirmed that the core–shell structure of the catalyst remained intact after durability testing. The approach may open a pathway for the design and preparation of high-performance inexpensive core–shell catalysts for a wide range of applications in energy conversion processes.Keywords: core−shell structure; fuel cells; oxygen reduction reaction; stability; transition metal nitride;

Transition metal nitrides have recently attracted significant interest as electrocatalysts for the oxygen reduction reaction (ORR) owing to their low electrical resistance and good corrosion resistance. In this paper, we describe the preparation of a Nb-based binary nitride material with a porous nanogrid morphology/structure. The catalyst exhibited good catalytic activity and high stability towards oxygen reduction. We also intensively investigated the effect that doping with a second transition metal had on the performance of the catalyst. We found that the ORR activity of NbN could be enhanced significantly by enriching the d electrons of Nb through doping with a second transition metal, and that doping with cobalt resulted in the best improvement. Our optimal catalyst, Nb0.95Co0.05N, had an ORR activity ∼4.6 times that of NbN (current density @ 0.6 V vs. the RHE). XPS results revealed that Co doping increased the proportion of Nb in a low-valence state, which may be one of the most important reasons for the enhanced performance. Another important reason is the high surface area resulting from the porous nanogrid morphology. As transition metal doping is an attractive way to enhance the activity of nitride catalysts, our work may provide an effective pathway to achieve this.

•Core-shell RuFeSe@Pt/C catalyst was prepared by a three-stage method.•RuFeSe@Pt/C exhibits high activity towards ORR.•RuFeSe@Pt/C has high methanol tolerance.•The ORR on RuFeSe@Pt/C catalyst goes through four-electron pathway.Pt decorated RuFeSe/C catalyst is prepared by reduction of Pt precursor on pre-formed RuFeSe/C for oxygen reduction reaction (ORR). The catalyst is characterized by X-ray diffraction (XRD), energy dispersive spectrometer (EDS), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The catalyst particles are found to disperse on the carbon support with an average particle size of 2.8 nm. Physical characterizations and electrochemical tests confirm that Pt is deposited on the surfaces of RuFeSe particles and RuFeSe@Pt/C catalyst has a core-shell structure. The as-prepared catalyst has high durability and shows high ORR activity through a four-electron transfer process. RuFeSe@Pt/C exhibits 1.3-fold greater specific activity and 1.4-fold greater mass activity for ORR than Pt/C. More importantly, it has excellent tolerance to methanol. Consequently, RuFeSe@Pt/C may be used as fine cathode catalyst in direct methanol fuel cells (DMFCs).

•A novel catalyst with atomic Pt layers covered on carbon nanotubes supported nitride NPs was synthesized.•The characterization results reveal the core-shell structure of the catalyst; with atomic Pt layers.•The catalyst exhibits roughly sixe times higher methanol oxidation activity than JM Pt/C catalyst.•The catalyst with nitride core results in the cost cutting and stability enhancement.•The addition of copper in the core greatly improved the catalyst’s methanol oxidation performance.In this study, a novel low-Pt core-shell catalyst is successfully prepared by depositing ultrathin Pt layer on the carbon nanotubes supported titanium nitride nanoparticles (TiN@Pt/CNTs) via a facile pulse electrochemical deposition approach. The catalyst is characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), High-angle annular dark field (HAADF) and energy-dispersive spectrometer (EDS) elemental mapping, X-ray photoelectron spectroscopy (XPS) and electrochemical measurements. The results confirm the core-shell structure of the prepared TiN@Pt/CNTs catalyst. More importantly, the catalyst exhibits superb mass activity and durability for the methanol oxidation reaction (MOR) than that of the commercial JM Pt/C catalyst. Later experiments data demonstrate that the activity and stability of the catalyst can be further enhanced via copper doping, which results from the modified electronic structure of the Pt atoms and the synergistic effects of the core-shell structure.The novel core-shell Ti0.9Cu0.1N@Pt/CNTs catalyst exhibits high methanol oxidation reaction activity and durability.Download high-res image (198KB)Download full-size image

•The performance of MEA can be enhanced by introducing N doped CNTs in CL and GDL.•The MEA with NCNTs in both CL and GDL simultaneously achieves best enhancements.•The current density at 0.7 V and 0.6 V is enhanced by 67 and 33% by adding NCNTs.•The max power density of our optimal MEA reaches 997 mW cm−2, enhanced by 28%.The performance of the proton exchange membrane fuel cell (PEMFC) is significantly improved through introducing nitrogen-doped carbon nanotubes (NCNTs) into the catalyst layer (CL) and microporous layer (MPL) of the membrane electrode assembly (MEA), it reveals by SEM images that the NCNTs are uniformly dispersed in CL and MPL, resulting in the more plenty of porosity, higher surface area, better conductivity, and better prevention of the layer cracks. The BET surface area and pore volume of MPL are increased by 88% and 77% respectively with the addition of 20 wt% of NCNTs in MPL. The membrane electrode assembly (MEA) with adding 20 wt% NCNTs both in cathode CL and in cathode GDL can yield the best cell performance. At a cell temperature of 70 °C and 30 psi back pressures, the current density is up to 1000 mA cm−2 at 0.7 V and 1600 mA cm−2 at 0.6 V, and the max power density reaches 997 mW cm−2.The MEA prepared by introducing nitrogen-doped CNTs (NCNTs) both in cathode CL and in cathode GDL exhibits excellent performance at cell temperature of 70 °C and 100% RH, the current density can be up to 1000 mA cm−2 at 0.7 V and 1600 mA cm−2 at 0.6 V, respectively, and the maximum power density reaches 997 mW cm−2, which is much higher than that of the MEA without NCNTs addition (781 mW cm−2).Download high-res image (210KB)Download full-size image

•Core-shell structured Ru@Pd/C catalysts were prepared for formic acid oxidation.•The Ru/C with distinct dispersion serves as active and robust cores of the catalyst.•A pulse electrodeposition method was used to fabricate the thin Pd shell of the catalysts.•The core-shell structure and the synergy contribute to the high performance.Core-shell structured Ru@Pd/C catalysts for the electrooxidation of formic acid are synthesized by an organic colloid method associated with a pulse electrodeposition process. The catalysts are characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM) and X-ray photoelectron spectroscopy (XPS). The electrocatalytic activity of the catalysts is evaluated by cyclic voltammetry, CO stripping and chronoamperometry technologies. The core-shell structure is revealed by both materials characterization and electrochemical methods, including STEM and energy dispersive X-ray spectroscopy (EDX), the binding energy difference of the XPS spectra and the potential shift of the CO stripping peaks. Such core-shell structured Ru@Pd/C catalysts show excellent activity towards the anodic oxidation of formic acid. The mass activity reaches 5.06 A mg−1Pd and 0.53 A mg−1metal which are ∼10.1 and 1.1 times that of commercial Pd/C. The encouraging performance of Ru@Pd/C is ascribed to the distinct dispersion of the Ru cores and the resulting Ru@Pd nanoparticles as well as the synergy between the core and shell that not only significantly enhances the ability to oxidize the formic acid but also improves the tolerance to CO.Download high-res image (85KB)Download full-size image

High-performance ferric phosphate (FePO4), with well-defined ellipsoid morphology and uniform particle size distribution, is successfully fabricated via a green spray drying method with formic acid as additive. It is found that the added formic acid plays a crucial role for the formation of the well-distributed FePO4 particles. Benefited by the outstanding structure and properties of ferric phosphate prepared above, a high performance of lithium iron phosphate (LiFePO4) has been prepared. It exhibits high capacity, especially at high charging/discharging rate (158.4 mAh g−1 at 0.2 C and 107.3 mAh g−1 at 10 C), and excellent cycling stability (without capacity fading after cycling for 200cycles at 1 C). All these impressive electrochemical performance could be ascribed to the FePO4 precursor, and further attributed to the addition of formic acid, which may play as a template, resulting in the well-defined morphology, uniform particles size distribution, hierarchical pore structure, and high surface area of the ferric phosphate.

Developing highly efficient and low-cost electrocatalysts for the oxygen reduction reaction (ORR) to substitute precious Pt-based catalysts is highly important for the commercialization of advanced electrochemical energy conversion systems. Doped carbons have attracted wide attention and have become one of the hottest topics in new energy fields due to their high ORR performance and low cost. In this work, uniform nitrogen and sulphur co-doped hollow carbon nanospheres with an ultra-high surface area (1060 m2 g−1) were fabricated by using polyacrylonitrile and sulphur as the precursors. The catalyst exhibits outstanding ORR performance, excellent stability, methanol tolerance, as well as high selectivity toward the four-electron catalytic pathway. By analyzing the effects of sulphur addition, we found that the sulphur addition is crucial for the formation of uniform nanospherical morphologies, as well as highly porous structures and high surface areas. Besides, sulphur addition was also found to be able to modify the catalysts' atomic compositions effectively by increasing the total and pyridinic N contents while reducing oxidized N contents. Sulphur addition induced unique features in the catalysts' structures and compositions. We believe that this should be the main origins of our catalyst's outstanding ORR performance.

Developing high-performance bifunctional electrocatalysts for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) using nonprecious metal-based catalysts is a major challenge for achieving the commercial success of regenerative fuel cells and rechargeable metal–air batteries. In the present study, we designed a new type of bifunctional catalyst by embedding cobalt sulfide hollow nanospheres in nitrogen and sulfur co-doped graphene nanoholes (Co1−xS/N–S–G) via a simple, one-pot pyrolysis method. The catalyst had a high specific surface area (390.6 m2 g−1) with a hierarchical meso–macroporous structure. In an alkaline medium, the catalyst exhibited high ORR catalytic activity, with a half-wave potential 30 mV more positive and a diffusion-limiting current density 15% higher than a commercial Pt/C catalyst, and the catalyst is also highly active for OER with a small overpotential of 371 mV for 10 mA cm−2 current density. Its overall oxygen electrode activity parameter (ΔE) is 0.760 V, which is smaller than that of Pt/C and most of the non-precious metal catalysts in previous studies. Furthermore, it demonstrated better durability towards both the ORR and OER. Detailed investigation clarified that the material's excellent electrocatalytic performance is attributable to: (1) a synergistic effect, induced by the presence of multiple types of active sites, including cobalt sulfide hollow nanospheres, nitrogen and sulfur dopants, and possible Co–N–C sites; (2) cobalt sulfide hollow nanospheres penetrating through the plane of graphene sheets form strong interaction between them; (3) more edge defects associated with the existence of nanoholes on the graphene basal plane; and (4) the high surface area and efficient mass transfer arising from the hierarchical porous structure.

We report a composite catalyst in which binary transition metal nitride nanoparticles (NPs) were mounted on nitrogen-doped reduced graphene oxide (TiCoNx/N-rGO). The catalyst exhibited outstanding oxygen reduction activity in an alkaline medium. In its optimal form, our catalyst yielded a half-wave potential of 0.902 V (vs. RHE), ∼30 mV more positive than that of the commercial Pt/C catalyst, and its current density at 0.9 V (vs. RHE) reached 2.51 mA cm−2. The ORR activity of our transition metal nitride-mounted N-rGO was much higher than the activities of transition metal nitride alone or N-rGO alone, revealing a strong synergistic effect between the two materials. Further, the catalyst mounted with Ti and Co binary NPs exhibited higher ORR activity than the catalyst mounted solely with Ti nitride NPs, indicating the significant improvement gained by the addition of cobalt. XPS analysis results showed that the mounting of transition metal nitride clearly changed the amount and distribution of N species in the catalyst, causing the percentage of active pyridinic-N species to increase significantly. Moreover, changes in the binding energies of C and Ti atoms proved the synergy between TiCoNx NPs and N-rGO. We therefore ascribe the superior electrochemical activity of our TiCoNx/N-rGO catalyst to this synergy and to the improvement resulting from the addition of Co. In addition to its outstanding ORR activity, this catalyst also showed excellent stability and methanol tolerance, making it a promising Pt-free ORR catalyst for alkaline H2/O2 fuel cells and direct methanol fuel cells.

•Palladium nanoflowers (PdNF) assembled of ultrathin Pd nanosheet was synthesized.•PdNF based low Pt catalyst was prepared by decorating Pt on the PdNF substrate.•The PdNF@Pt catalyst exhibited much higher ORR mass activity than commercial Pt/C.A three-dimensional, low platinum (Pt) catalyst was prepared by decorating platinum on the palladium nanoflowers (PdNF) by an underpotential deposition (UPD) method. The PdNF was synthesized by a solvothermal approach, using oleic acid as the template and benzyl alcohol as the solvent-reducing agent. The obtained Pd with a morphology of uniform nanoflowers is composed of plentiful nanosheets. After decorating with platinum, the catalyst PdNF@Pt exhibits much higher activity for the oxygen reduction reaction (ORR) compared to commercial Pt/C (Pt 20 wt%). The interaction between deposited Pt and PdNF was revealed by XPS analysis, and the high performance of the PdNF@Pt catalyst was attributed to following two aspects: the increased of dispersion of platinum based on PdNF substrate, and the increased intrinsic activity of the active sites caused by the interaction of Pt and Pd NF.

•PdM (M = Fe, Co, Ni) alloy nanoparticles decorated on nitrogen-doped reduced graphene oxide as catalysts for Li–O2 batteries.•The addition of transition metals significantly improved catalytic stability.•The Pd alloy nanoparticle aggregation and dissolution was prevented by the addition of Fe.An efficient ORR/OER catalyst was developed by anchoring highly dispersed bimetallic PdM (M = Fe, Co, Ni) alloy nanoparticles on nitrogen-doped reduced graphene oxide (N-rGO). This new type of catalyst exhibited excellent ORR/OER activity, and the addition of transition metals also significantly improved catalytic stability, with the catalyst containing Fe (PdFe/N-rGO) exhibiting the best stability. A battery using this PdFe/N-rGO catalyst was capable of long-term stable cycling for 400 cycles (2000 h) with a limited capacity of 1000 mAh g−1 at 400 mA g−1, which was much longer than a battery with Pd/N-rGO as the catalyst (only 80 cycles, 400 h). We attribute the high performance of these catalysts to the high surface area of N-rGO, the anchoring of highly dispersed Pd alloy nanoparticles, and the prevention of Pd alloy nanoparticle aggregation and dissolution by the presence of the transition metals.

•Ir@Pt NPs in the cathode is prepared by an in-situ pulse electrodeposition method.•Novel MEA exhibits excellent single cell performance with ultra-low Pt loading.•High Pt exposure and synergistic effect of Pt and Ir may lead to high performance.•DFT calculations reveal the interaction between Pt shell and Ir core.A novel membrane electrode assemblies (MEAs) with ultra-low Pt loadings and high Pt exposure in the cathode layer is prepared by spraying Ir/C catalyst ink on the membrane surface to form a substrate layer, followed by in situ pulse electrochemical deposition of a Pt shell layer on the Ir core nanoparticles in the substrate layer. It makes the Pt loadings on cathode lower to 0.044 mg/cm2. In our system, the MEA with our novel cathode exhibits excellent performance in a H2/air single fuel cell, which is comparable to that of the MEA prepared with commercial Pt/C catalyst (Johnson Matthey 40% Pt) with Pt loadings of 0.1 mg/cm2. The electrode with core–shell structured catalysts is characterized by X-ray diffraction, X-ray photoelectron spectroscopy, EDS line-scan, and scanning transmission electron microscopy. Based on the characterization results, it is found that the Pt is highly dispersed on the Ir NPs, and the electronic feature of Pt at shell layer can be tuned by the Ir core particle. Furthermore, the DFT calculation results also reveal the interaction between Pt at shell layer and Ir core. This work may provide a novel pathway to realize low Pt and high Pt utilization in low temperature fuel cells.Download high-res image (237KB)Download full-size image

•Binary Fe- and Cu-codoped carbon nanotubes was proposed as efficient catalyst for ORR.•The Fe-Cu-N/C catalyst exhibits uniform bamboo-like morphology, high surface area and hierarchical porous structure.•The doping of Cu into Fe-N-C architecture was found to effectively tune the electronic structure.•The Fe-Cu-N/C catalyst exhibits superior activity and stability to commercial Pt/C in 0.1 M KOH and HClO4 solution.In this work, CuCl2 as a promoter was added into the mixture of polythiophene (PTh), FeCl3, and melamine for preparing Fe-Cu-N/C catalyst. The catalyst features one-dimensional bamboo-like carbon nanotubes with few metal oxide nanoparticles encapsulated into tubes. The catalyst exhibits excellent activity toward the oxygen reduction reaction (ORR) with half-wave potential 50 mV more positive than the commercial Pt/C in 0.1 M KOH. It also shows comparable ORR activity in 0.1 M HClO4 solution. Moreover, it exhibits superior long-term stability and excellent methanol tolerance in both alkaline and acidic solutions. The outstanding catalytic performance of Fe-Cu-N/C catalyst can be ascribed to the doping of Cu in the Fe-N-C architecture, which promotes the formation of bamboo-like nanotube structure and the generation of interaction among Cu and Fe-N-C. This synthetic strategy may open new avenues for constructing highly efficient electrocatalysts that adding of an inactive metal can obviously promote the catalytic performance of catalysts.Download high-res image (228KB)Download full-size image

The main challenges to the commercial viability of polymer electrolyte membrane fuel cells are (i) the high cost associated with using large amounts of Pt in fuel cell cathodes to compensate for the sluggish kinetics of the oxygen reduction reaction, (ii) catalyst degradation, and (iii) carbon-support corrosion. To address these obstacles, our group has focused on robust, carbon-free transition metal nitride materials with low Pt content that exhibit tunable physical and catalytic properties. Here, we report on the high performance of a novel catalyst with low Pt content, prepared by placing several layers of Pt atoms on nanoparticles of titanium nickel binary nitride. For the ORR, the catalyst exhibited a more than 400% and 200% increase in mass activity and specific activity, respectively, compared with the commercial Pt/C catalyst. It also showed excellent stability/durability, experiencing only a slight performance loss after 10 000 potential cycles, while TEM results showed its structure had remained intact. The catalyst’s outstanding performance may have resulted from the ultrahigh dispersion of Pt (several atomic layers coated on the nitride nanoparticles), and the excellent stability/durability may have been due to the good stability of nitride and synergetic effects between ultrathin Pt layer and the robust TiNiN support.

In the semiconductor photocatalyst system for overall water splitting, cocatalysts play crucial roles because they provide not only redox active sites but also charge separation function for photogenerated electrons and holes. In this work, we have investigated the cubic structured NaTaO3 with six equivalent {001} facets to address the following two important questions: Can charge separation occur among the equivalent facets? How can photogenerated charges be separated on the equivalent surface for photocatalytic reactions? Charge location probe experiments by photodepsotion of noble metals and metal oxides show that no spatial charge separation occurs among the six equivalent facets of NaTaO3. However, observation of efficient overall water-splitting reaction upon loading of well-known cocatalyst NiO on the NaTaO3 clearly demonstrates that photogenerated electrons and holes could still be well-separated. In-situ formation of Ni and NiO cocatalysts during the water-splitting process was revealed by X-ray photoelectron spectroscopy and synchrotron X-ray absorption spectroscopy, confirming the role of dual cocatalysts Ni/NiO, where nickel serves as an electron trap (catalytic sites for proton reduction) and NiO serves as a hole trap (catalytic sites for water oxidation). Such vicinal charge separation by dual cocatalysts leads to efficient overall water splitting.Keywords: charge separation; dual cocatalysts; equivalent facets; hydrogen production; overall water splitting; photocatalysis

The poor catalytic activity of early-transition-metal nitrides has prevented them from being competitive catalysts toward the oxygen reduction reaction (ORR). In the present study, we first explored the limitations for early-transition-metal nitrides as competitive catalysts in the view of O2 dissociation, finding that the limitations include insufficient d electrons (in the case of ScN, TiN, and VN) and unsuitable surface geometric structure (in the case of CrN), both of which can result in no O2 dissociation on early-transition-metal nitrides. Then on the basis of the above knowledge, we took VN as an example and proposed a strategy to enhance its ORR activity by enriching its d electrons through doping with 3d transition metals. The doped VN showed greatly enhanced ORR activity, with Co-doped VN exhibiting the best performance; its ORR activity was close to that of JM 20 wt % Pt/C. X-ray photoelectron spectroscopy (XPS) clearly revealed that Co doping significantly increased the proportion of V in a low-valence state. O2 temperature-programmed desorption (O2-TPD) measurements also presented some very important information induced by doping. Our theoretical analysis and experimental studies indicated that early-transition-metal nitrides with insufficient d electrons can be promising ORR catalysts via the strategy of enriching their d electrons through doping elements with rich d electrons.Keywords: d electrons; early-transition-metal nitrides; fuel cells; O2 dissociation; oxygen reduction reaction

A hollow spherical doped carbon catalyst with a large surface area and hierarchical porous structure is prepared by pyrolyzing zeolitic imidazolate framework nanocrystals (Z8Ncs) impregnated/covered with iron phthalocyanines (FePcs). It is found that the doping of FePcs into the Z8Nc precursor plays a crucial role in the structural evolution of the resulting hollow-core porous carbon as well as its high catalytic performance. Doped carbon catalysts derived from either Z8Ncs or FePcs exhibit poor activity towards oxygen reduction, whereas the catalyst derived from Z8Ncs impregnated/covered with FePcs exhibits extremely high performance in both acidic and alkaline media. In 0.1 M HClO4, its onset potential reaches up to 0.910 V, and its half-potential (0.790 V) is only 60 mV lower than that of the 20 wt% Pt/C catalyst (0.850 V). In 0.1 M KOH, its ORR activity even surpasses that of Pt/C. We suggest that the high performance of the catalyst is attributable to the following factors: (i) the high active site density caused by doping FePcs into/onto the highly porous, N-rich Z8Ncs, (ii) the high surface area and adequate active site exposure caused by its hollow spherical morphology, and (iii) the hierarchical porous structure which further facilitates the diffusion and adsorption of oxygen molecules.

A core–shell structured catalyst, Pd1Ru1Ni2@Pt/C, with a ternary alloy as its core and a Pt monolayer shell was prepared using a two-stage strategy, in which Pd1Ru1Ni2 alloy nanoparticles were prepared by a chemical reduction method, and then the Pt monolayer shell was generated via an underpotential deposition method. It was found that the addition of Ni to the core played an important role in enhancing the catalyst's oxygen reduction activity and stability. The optimal molar ratio of Pd:Ru:Ni was about 1:1:2; the catalyst with this optimal ratio had a half-wave potential approximately 65 mV higher than that of a PdRu@Pt/C catalyst, and its mass activity was up to 1.06 A mg−1 Pt, which was more than five times that of a commercial Pt/C catalyst. The catalyst's structure and composition were characterized using X-ray powder diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and energy-dispersive X-ray spectrometry. The core–shell structure of the catalyst was demonstrated by the EDS mapping results and supported by the XPS results. We also performed a stability test that confirmed the catalyst's superior stability in comparison to that of commercial JM Pt/C (20 wt% Pt).

•A facile method for highly active ORR electrocatalysts with high porosity and surface areas.•The catalyst’s ORR performance is much more superior to that of commercial Pt/C catalyst.•It is one of the best ORR catalysts in alkaline medium to date as far as we know.A highly porous N self-doped carbon catalyst, with three dimensional morphology/structures and high surface area (810.8 m2 g−1), is prepared through a pyrolysis procedure with polyacrylonitrile as the precursor, and zinc oxide (ZnO) as the templates/pore former. The catalyst exhibits excellent activity and stability towards oxygen reduction reaction (ORR) in alkaline medium, as well as outstanding methanol tolerance and stability. For our optimal catalyst PAC/ZnO-900, its half-wave potential is 26 mV more positive (0.859 V, vs. RHE) than that of commercial Pt/C catalyst (0.833 V, vs. RHE), and its current density at 0.88 V (vs. RHE) is almost twice as high as that of Pt/C catalyst (−1.922 and −0.957 mA cm−2, respectively). It is found that the addition of ZnO plays a crucial role for the formation of catalysts’ 3D porous structures and high ORR performance. With the addition of ZnO in precursor, the surface area of the catalyst is enhanced by 13 times, and the ORR activity is enhanced by 10 times. Also, pyrolyzing temperature seems to be another important factor significantly affected the structure and performance of the catalyst.Highly active electrocatalyst for oxygen reduction, with high porosity and surface area, derived from polyacrylonitrile.

Reduced graphene oxide co-doped with nitrogen and fluorine (N–F/rGO) was successfully prepared by a simple one-step thermal annealing process using a mixture of graphene oxide and ammonium fluoride in an argon atmosphere. X-ray photoelectron spectroscopy demonstrated that the nitrogen and fluorine atoms were successfully doped into the rGO structure at atomic percentages of 2.51 and 0.74, respectively. Nitrogen adsorption–desorption measurement revealed that the as-prepared N–F/rGO has a high surface area (412 m2 g−1) with numerous slit-shaped pores (1.60 cm3 g−1). The electrocatalytic activity of N–F/rGO for oxygen reduction reaction was found to be higher than that of rGO doped only with nitrogen (N/rGO); in fact, it was comparable to the activity of conventional commercial Pt/C in an alkaline electrolyte. In addition, the catalyst exhibited excellent long-term stability/durability, good methanol tolerance, and high selectivity for the four-electron transfer pathway. A possible mechanism is suggested for the improvement conferred by fluorine.

Ni, Mo co-doped LiMn2O4 cathode materials for lithium-ion batteries were prepared using a high-temperature solid-state method. The materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM),and electrochemical impedance spectroscopy. The original material’s performance was significantly enhanced by co-doping. The sample with optimal composition, LiNi0.03Mo0.01Mn1.96O4, had a discharge capacity at1C of 114 mAhg−1, which was 8.6% higher than that of undoped LiMn2O4. Importantly, this doped material exhibited significantly improved stability: after 300 charge–discharge cycles at 1C, its capacity retention was 91.2%, whereas the capacity retention of the undoped LiMn2O4 was only 61.9% after 300 cycles. SEM images and XRD patterns showed no obvious morphological changes in the co-doped material after cycling, implying that it had high structural stability. We suggest that this material’s significantly improved electrochemical performance was probably caused by reduced Mn3+ dissolution and decreased Li+ intercalation and de-intercalation resistances.

•Co and N co-doped graphene mounted with IrO2 nanoparticles was prepared.•The catalyst showed high capacity and good cycling stability in a Li-O2 battery.•The mounting of IrO2 significantly enhanced the OER performance of doped graphene.•The ORR activity apparently was improved by co-doping graphene with Co and N.In this work, a high-performance composite catalyst comprised of IrO2 nanoparticles mounted on Co and N co-doped reduced graphene oxide (Co-N-rGO) is designed and successfully prepared for use in a Li-O2 battery. A battery with this catalyst as the cathode demonstrates very high capacity retention ability and cycling stability: it delivered a high reversible capacity of 11,731 mAh g−1 after five cycles at 200 mA g−1, and after 200 cycles with limited capacity of 600 mAh g−1, the battery’s discharge terminal voltage remains over 2 V and its energy efficiency still above 65%. Doping with Co and N, along with mounting the IrO2 nanoparticles, greatly enhances the catalyst’s performance. We suggest that its outstanding performance is attributable to the high surface area of rGO, the enhanced oxygen reduction reaction (ORR) activity arising from doping with Co and N, and the high dispersion and great promotion of IrO2 nanoparticles.

It is highly desirable but remains challenging to develop efficient bifunctional electrocatalysts for both the oxygen reduction and oxygen evolution reactions (ORR/OER) in rechargeable metal–air batteries and unitized regenerative fuel cells. Herein, we developed a facile and cost-effective strategy to prepare a cobalt and nitrogen codoped three-dimensional (3D) graphene catalyst through inserting carbon nanospheres into the interlayers of graphene sheets. The catalyst exhibited not only excellent ORR performance but also excellent OER performance, and both were greatly enhanced by the insertion of carbon nanospheres. Its activities for the ORR/OER ranked among the best for doped carbon catalysts thus far reported. Its overall oxygen electrode activity parameter (ΔE) was as low as 0.807 V, which was much lower than that of Pt/C, and made it comparable with the best nonprecious metal based catalysts to date. Furthermore, the catalyst exhibited excellent stability toward ORR and OER, making it a new noble-metal-free bifunctional catalyst for future applications in the fields of alternative energy conversion and storage systems.Keywords: Carbon nanospheres; Cobalt and nitrogen codoping; Graphene; Insertion; Oxygen evolution reaction; Oxygen reduction reaction

In this work, nitrogen self-doped porous nanoparticles were synthesized through a low cost and simple method with spiral seaweed as a source of nitrogen and carbon. Transmission electron microscopy (TEM), nitrogen adsorption–desorption, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analysis showed that nitrogen was successfully doped into the framework of porous nanostructures. The nitrogen self-doped porous nanomaterial featured a high surface area and micro/mesoporous structures. The fabricated nanomaterial was then used as a metal-free catalyst for oxygen reduction reaction (ORR). This catalyst exhibited improved electrocatalytic activity, long-term operation stability, and high CH3OH tolerance for ORR in alkaline fuel cells compared with commercial Pt/C catalysts. The influence of different nitrogen species formed in different atmospheres on ORR activity was further investigated. This study shows that spirulina is a suitable nitrogen and carbon source for various carbon-based materials for the development of metal-free efficient catalysts for applications beyond fuel cells.

In this study, using a template (Pluronic P123) as an in situ carbon source, ordered mesoporous carbons (OMC) were successfully synthesized through directing carbonization of templates. Two key factors in the morphology evolution of mesoporous carbon materials were introduced, one is the tailoring role of micelles by ethanediol, and the other is the dehydrated cross-linking effect by sulfuric acid. Through the two factors, the morphology of as-synthesized ordered mesoporous carbons can be altered from bulks to rods and even to sheets. Transmission electron microscopy (TEM) showed ordered mesoporous carbon rods (OMCR) and ordered mesoporous carbons sheets (OMCS) possessed regular morphology and good mesopore structure. Nitrogen adsorption–desorption analysis confirmed that both OMCR and OMCS had high surface area and uniform mesopore distribution, OMCR had the highest surface area (919 m2 g−1) and OMCS had the biggest pore size (9.11 nm). This study also showed that OMCR and OMCS were good carbon carriers; the size of Pt loading nanoparticles can be decreased to 3 nm and Pt/OMCS especially presents very high Pt dispersion and uniformly smallest Pt nanoparticles (2.49 nm).

•A air-breathing cathode was prepared with mixture of Pt/CNT and Pt/C as catalyst.•The performance of air-breathing PEMFC with the cathode is enhanced significantly.•The porosity and water management are improved through inducing Pt/CNTs catalyst.It is well recognized that pore structure and the hydrophilicity/hydrophobicity balance are key factors for the cathodes of air-breathing proton exchange membrane fuel cells (AB-PEMFCs). In this work, we attempted to adjust the pore structure and hydrophilicity of an air-breathing cathode by using two types of catalysts, Pt/C and Pt/CNT, to prepare the catalyst layer for the air-breathing cathode instead of using a single catalyst. An MEA with the dual-catalyst cathode exhibited significantly improved single-cell performance, which was affected by the ratio of Pt/C to Pt/CNT. Our optimized MEA, which had a ratio of 54:46 in the cathode catalyst layer, achieved a current density of up to 290 mA cm−2 at 0.6 V, which was 14% higher than that of a MEA without Pt/CNT. The Pt/CNT in the catalyst layer played the key role in the overall performance of the AB-PEMFC. We propose that the CNT improved charge transfer and enabled better electrical conductivity than carbon black. In addition, the tubular structure of Pt/CNT made the catalyst layer more porous and permeable to gas. Furthermore, the addition of Pt/CNT may have changed the cathode's hydrophilicity/hydrophobicity balance, giving the cathode better water balance and consequently yielding better performance.A high performance air-breathing cathode for air-breathing PEMFCs is prepared by using the mixture of Pt/C and Pt/CNTs as cathode catalysts. The significantly enhanced performance has been achieved by the PEMFC with the cathode.

•A heteroatoms-doped biocarbon spheres are prepared with brewer's yeast powder as precursor.•The addition of Fe plays a crucial role for the formation of spherical morphology.•The spheres are abounded with heteroatoms (N, O, P, Fe) and hierarchical porosity.•The material shows superior ORR activity to 20 wt.% Pt/C (JM) catalyst in KOH solution.A high-performance, spherical, heteroatom-doped carbon catalyst for the oxygen reduction reaction (ORR), with a porous structure and a high surface area, has been prepared through a hydrothermal treatment process and subsequent carbonization procedures using brewer's yeast powder, ferric chloride, and ammonium hydroxide as precursors. We found that the addition of iron had a significant effect on the catalyst's spherical morphology and ORR activity. Electrochemical measurements demonstrated that the catalyst has excellent ORR performance, with a half-wave potential 28 mV more positive (0.861 V vs. RHE) than that of commercial 20 wt.% Pt/C (0.833 V vs. RHE) in an alkaline medium. The catalyst also displays remarkable methanol tolerance and durability. The abundance of active N and P species and the porous structure may be responsible for this catalyst's high ORR performance. The present work provides a facile way of using economical, environmentally friendly, and renewable biomass to develop a high-activity cathode electrocatalyst for fuel cell applications.A heteroatoms-doped hollow biocarbon spheres with high surface area and hierarchical porous structure were successfully prepared by hydrothermal treating and followed pyrolyzing the mixture of brewer's yeast powder, ferric chloride and ammonium hydroxide. The catalyst displays excellent ORR catalytic activity in alkaline medium, with a 28 mV positive shift (0.861 vs. 0.833 V) in half-wave potential compared to that of commercial 20 wt.% Pt/C (JM).

•Self-humidification MEA is fabricated with home-made Pt/SnO2–SiO2/C anode catalyst.•The MEA shows good self-humidification performance at 60 °C and 10% RH.•The current density is up to 1050 mA cm−2 at 0.6 V at 60 °C and 10% RH condition.•The long term testing of 96 h reveals the good stability of the MEA at low RH.A novel self-humidifying membrane electrode assembly (MEA) with homemade multi-functional Pt/SnO2–SiO2/C as the anode was developed to improve the performance of a proton exchange membrane fuel cell under low humidity. The MEAs' performance was evaluated at various temperatures and relative humidity levels. One MEA with a Pt/SnO2–SiO2/C anode catalyst achieved excellent low-humidity performance at a cell temperature of up to 60 °C: the current density reached 600 mA cm−2 at 0.7 V and 1050 mA cm−2 at 0.6 V with 10% RH; after 96 h of continuous operation under the same conditions, the current density decreased by only 16% (to ∼880 mA cm−2), whereas the current density of an MEA with JM Pt/C as the anode degraded by more than 60% within 10 h. The contact angle of the Pt/SnO2–SiO2/C anode was much lower than that of the Pt/C anode, indicating the former's excellent wettability. The high performance of the MEA with the Pt/SnO2–SiO2/C anode is attributable to the wettability of the doped binary oxide, especially of silicon oxide, and the promotion of tin oxide, which caused an interaction between the Pt and the oxide, resulting in enhanced performance under low humidification.The MEA prepared by home-made multi-functional Pt/SnO2–SiO2/C as the anode catalyst exhibits high and stable self-humidification performance at cell temperature of 60 °C and 10% relative humidity, the current density at 0.6 V can be up to 1050 mA cm−2 and stable at 880 mA cm−2 after 96 h continuous running, with the degradation of 16%, which is much better than that of the blank MEA without insertion.

Lithium-rich layered nickel–manganese oxide (LRL-NMO) as a cathode material for rechargeable lithium-ion batteries was successfully prepared using an oxalic acid co-precipitation method, with polyethylene glycol (PEG1000) as an additive. The effects of the Ni/Mn ratio and of PEG on the phase purity, morphology, and electrochemical performance of LRL-NMO were investigated with X-ray diffraction, scanning electron microscope, electrochemical impedance spectroscopy, and charge/discharge testing. Li[Li0.167Ni0.25Mn0.580]O2 delivered the best electrochemical performance among the various Li[Li1/3−2x/3NixMn2/3−x/3]O2 (0 < x < 0.5) materials. Furthermore, the sample to which an appropriate amount of PEG had been added showed much smaller and more uniform particle size, higher discharge capacity and energy density, better cycling stability, and lower resistance. The material prepared by adding 9 wt% PEG exhibited high discharge capacity and stability; after 100 cycles at 2 C, it still delivered a discharge capacity of 125.6 mAh g−1, which was 50 % higher than that of a sample prepared without PEG.

Poor durability is one of the two major problems hindering the commercialization of proton exchange membrane fuel cells, due to Pt nanoparticle aggregation in the electrocatalyst and corrosion of its carbon support. In this paper, we report a Pt electrocatalyst in which carbon black decorated with a tin and silicon binary oxide layer was used as the support, with SnO2 as a promoter and SiO2 as a stabilizer. Transmission electron microscopy revealed that the binary oxide formed a thin layer on the surface of the carbon support particles. The catalyst exhibited significantly enhanced performance toward the oxygen reduction reaction (ORR): at 0.9 V (vs RHE), the ORR current density was ∼1.5 times higher than that of a commercial JM Pt/C catalyst with the same Pt loading. Furthermore, it showed excellent durability, again better than that of JM Pt/C: after 8000 cyclic voltammetry cycles in 0.5 M H2SO4 solution, the electrochemically active surface area was almost unchanged and the ORR half-wave potential shifted by only 10 mV. We attribute the catalyst’s high activity and durability to the binary oxide coating the surface of the carbon nanoparticles. We suggest it may play two roles: (1) promoted by tin oxide and thereby enhancing the catalytic activity and (2) preventing the Pt nanoparticles from aggregating and carbon support from corrosion. The high ORR performance and excellent stability of this catalyst make it promising for use in practical fuel cell applications.Keywords: binary oxide; carbon support; decorate; durability; ORR; Pt electrocatalyst

An ultralow platinum loading membrane electrode assembly (MEA) is prepared by a facile synthesis process in which pulse electrodeposition is used to achieve a catalyst layer by the in situ decoration of carbon-supported Pd nanoparticles with a thin layer of Pt atoms. The novel MEA exhibits excellent performance in a H2/air single fuel cell, with Pt loading of as little as 0.015 mg cm–2 at the anode and 0.04 mg cm–2 at the cathode, outperforming the commercial Pt/C MEA (Johnson Matthey, 40 wt % Pt). The shift in binding energy of the XPS peak of Pd and Pt in the Pd@Pt/C MEA confirms the presence of the Pt shell and the interaction between the shell and the Pd core. We suggest that the high performance of this Pd@Pt/C MEA may be due to several factors: high Pt dispersion arising from the core–shell structure, high Pt utilization because there is no Nafion binder covering the Pt, the quantum effect caused by the high distribution of Pt, and the interaction between the Pt shell and the Pd in the core.Keywords: core−shell structure; fuel cell; membrane electrode assembly; pulse electrodeposition; ultralow platinum

Three-dimensional palladium nanoflowers (Pd-NF) composed of ultrathin Pd nanosheets were synthesized by a solvothermal approach. The Pd-NF catalyst shows 6.6- and 5.5-fold enhancements in mass activity and surface activity compared to normal palladium nanoparticles (Pd-NP) in the electro-oxidation of formic acid.

A novel high-performance air cathode was prepared by synthesizing Co3O4 nanowire clusters on a nickel foam (NF) substrate and then decorating these clusters with Pd nanoparticles using a pulse electrodeposition method. This carbon-free and binder-free cathode had a well-defined, flower-like morphology, presenting clusters composed of nanowires with a diameter of ∼60 nm and a length of ∼5 μm on which were located Pd particles as small as 10 nm. The new cathode exhibited excellent low polarization and superior cycling performance. We found that its enhanced electrochemical properties could be attributed to the homogeneous distribution of Pd nanoparticles on the Co3O4 nanowires, which ensured uniform growth of Li2O2 on the Pd/Co3O4/NF electrodes. This, in turn, significantly improved the cathode's OER/ORR activity and aided the formation of discharge products with uniform morphologies, as well as the decomposition of these discharge products during recharging.

With a novel two-step approach, we prepared a low-cost, high-performance, binary transition metal nitride (BTMN) catalyst. An ammonia (NH3) complex of Ti and a transition metal was prepared in an organic solvent by the reaction of metal ions with ammonium; the complex then was dried in a vacuum oven, followed by nitridation in a tubular furnace under NH3 flow. The catalyst exhibited excellent activity towards the oxygen reduction reaction (ORR) in an alkaline medium and good ORR activity in an acidic medium. The effects of the doping elements (Fe, Co, and Ni), the doping concentration, and various nitriding temperatures on catalytic performance were intensively investigated. The onset potential of the Ti0.95Ni0.5N catalyst reached 0.83 V, with a limiting diffusion current density of 4 mA cm−2 (at a rotation speed of 1600 rpm) in 0.1 M HClO4 solution, which is the highest to date among the reported TiN-based electrocatalysts in an acidic medium. In 0.1 M KOH solution, the performance of this catalyst was almost comparable to that of commercial JM Pt/C; the diffusion current density reached 5.3 mA cm−2, and the halfway potential was only 71 mV inferior to that of commercial JM Pt/C. Furthermore, the catalyst showed high stability and only a slight drop in its current density after the durability test. All of these findings make our BTMN catalyst attractive for PEMFCs.

Developing a high-performance Li–O2 battery demands an air electrode with a high-efficiency bifunctional catalyst. Here we designed a new type of bifunctional cathode catalyst by mounting ruthenium nanoparticles on reduced graphene oxide co-doped with nitrogen, iron, and cobalt. The catalyst exhibited significantly higher ORR and OER activities than a commercial Pt/C catalyst in both aqueous and non-aqueous electrolytes. With this novel catalyst as the cathode, the battery exhibited an ultra-high reversible capacity of 23905 mA h g−1 at a current density of 200 mA g−1. Furthermore, the battery also exhibited an excellent cycling stability—after 300 cycles of limited capacity, the discharge plateau potential decreased only slightly, and the energy efficiency was still above 60%. The battery also demonstrated good rate performance; with discharge current densities of up to 1000 and 2000 mA g−1, the capacities still reached 14560 and 6420 mA h g−1, respectively. We suggest that the excellent performance of our catalyst can be ascribed to the excellent ORR performance of the multielement co-doped graphene and the excellent OER performance of the mounted Ru nanoparticles. In addition, the nanosheet structure with high surface area of the multielement co-doped graphene may result in the formation of uniform Li2O2 nanocrystals, which make the formation (discharge) and decomposition (charge) processes much more reversible.

A high performance doped carbon catalyst with ordered mesoporous structures and a high surface area (1217 m2 g−1) was prepared through a nanocasting-pyrolysis procedure by using poly(4-vinylpyridine) and iron chloride as the precursors and SBA-15 as the template. The catalyst exhibited excellent oxygen reduction reaction (ORR) performance, and was far more active than a commercial Pt/C catalyst in alkaline media, with its half-wave potential (−0.083 V, vs. Ag/AgCl) 64 mV more positive and current density at −0.1 V (vs. Ag/AgCl, −3.651 mA cm−2) almost three times higher than those of a commercial Pt/C catalyst (−0.147 V, vs. Ag/AgCl, and −0.967 mA cm−2), respectively. To our knowledge, it is one of the best carbon-based ORR catalysts to date in an alkaline medium. In addition to the outstanding ORR performance, our catalyst also illustrated excellent stability, methanol tolerance, and high catalytic efficiency. It is found that the total N contents and the compositions of each N species in the catalysts strongly depend on the pyrolysis temperatures. Furthermore, we found that the SBA-15 templates not only give catalysts well-defined mesoporous structures, but also seem to help increase the total N content whilst the proportion of each N species in the catalysts is not changed obviously.

•N, P and Fe co-doped carbon nanospheres were prepared by a facile method.•The catalyst shows a high surface area and hierarchical porous structure.•The catalyst exhibits excellent ORR performance superior to the Pt/C catalyst.Nitrogen, phosphorus and Fe doped carbon nanospheres have been synthesized by a facile method in which polyacrylonitrile nanospheres are pyrolyzed in the presence of diammonium phosphate and iron trichloride hexahydrate. The specific surface area of the catalyst is high up to 771.3 m2 g−1, and it has a hierarchical micro-meso-macroporous structure. In an alkaline medium, the catalyst exhibits high electrocatalytic activity towards the oxygen reduction reaction (ORR) as well as excellent stability and methanol tolerance—superior in each case to commercial Pt/C catalyst. The effects that adding Fe salt and phosphorus on the structure and performance of the catalyst are also investigated. We suggest that the catalyst's excellent electrocatalytic performance may be attributed to: (1) the synergistic effect, which provides more catalytic sites for the ORR, due to the nitrogen and phosphorus co-doping; (2) the strong promotion by trace Fe residues; and (3) the high surface area and excellent mass transport rate arising from the hierarchical porous structure.

•A highly performance membrane electrode assembly was prepared by ALD technique.•The platinum atoms were deposited on the gas diffusion layer directly.•The ALD-electrode achieved 2.5 times mass activity of the conventional electrode.A high-performance membrane electrode assembly (MEA) with low platinum loading was successfully prepared using an atomic layer deposition (ALD) technique, in which the platinum was directly deposited on the gas diffusion layer to form the catalyst layer. MEAs were fabricated with an ALD-prepared electrode as the anode, and assembled with pretreated Nafion® membrane (Nafion® 117) and a commercial cathode. The MEAs were evaluated in a single-cell test station and characterized by cyclic voltammetry (CV), field-emission scanning electron microscope (FE-SEM), high-resolution transmission electron microscope (HRTEM) and grazing incident X-ray diffraction (XRD). The results revealed that the active component, Pt, was highly dispersed in the ALD anode, and the MEA with the ALD anode showed excellent activity and stability. The mass activity reached 4.80 kW g Pt−1, which was 2.53 times higher than that of the MEA with the anode prepared using the commercial catalyst and a conventional screen printing method. In 100 h of durability testing, the ALD–MEA exhibited excellent durability (98.2% voltage retention) compared with the CC–MEA (92.5% voltage retention) when the MEA was discharged at a current density of 400 mA cm−2. The high performance, along with low platinum loading and high platinum utilization, make the ALD technique promising for use in PEM fuel cells.

•Electrolessly-plated copper foams were synthesized for preparation of N, P and B doped CNFs.•Doped CNFs were hydrophilic and employed as supports to anchor Pt without any functionization.•Pt/CNF was highly active and stable for ORR and was resistant to corrosion.Aimed at improved durability and catalytic activity for oxygen reduction reaction, carbon nanofibers(CNFs) with nitrogen, phosphorus and boron dopants have been synthesized by chemical vapor deposition of acetylene on electrolessly-plated copper foams. The as-prepared CNFs were extensively characterized by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy and Raman analysis. Without any functionalization, the as-prepared CNF was employed as support for 40 wt.% Pt electrocatalyst (Pt/CNF). In an accelerated stability test (AST), Pt/CNF displayed higher stability relative to the state-of-the-art electrocatalyst from Johnson Matthey (Pt/C-JM) with the same Pt loading. TEM images after AST for Pt/CNF were obtained and found that the doped carbon nanofiber support is more resistant to corrosion. At the meantime, the catalytic activity to oxygen reduction for Pt/CNF surpassed Pt/C-JM by more positive on-set potential. CNFs with N, P and B dopants synthesized in this work should have promised applications for polymer electrolyte membrane fuel cells.

•A self-humidifying MEA is prepared by inserting a MCC layer between CL and GDL.•The MEA exhibits good self-humidification performance at the humidity lower to 30%.•Self-humidification performance can be kept at the cell temperature up to 70 °C.•The MEA presents good stability at low humidity and high cell temperature.A high-performance self-humidifying membrane electrode assembly (MEA) was prepared by inserting hygroscopic microcrystalline cellulose (MCC) between the gas diffusion layer (GDL) and the catalyst layer (CL). At low humidity, the MEA exhibited good self-humidification, including high output and good stability. With our optimal MEA, in which the MCC loading was ca. 0.5 mg cm−2, the current density at 0.6 V reached 1100 mA cm−2 and the maximum power density was 751 mW cm−2, at a relative humidity (RH) of 30% for both anode and cathode gases and a cell temperature of 70 °C; the performance was comparable to that of a MEA prepared without added MCC and operated at 100% RH. Further, after 24 h of operation at low humidity and 0.6 V, the MEA's current density decreased by only 9.1%, compared with the 60% decline experienced by the MEA without MCC after 3 h under the same conditions, demonstrating the former's good self-humidification stability. When we attempted to insert the MCC layer elsewhere, including between the membrane and the anode CL, we found that inserting it between the GDL and the anode CL yielded the best performance. The high self-humidification performance of this MEA is attributable to the strong wettability and water-retention capacity of MCC. The MCC layer between the GDL and the anode CL ensured the latter would remain sufficiently wet and accelerated hydrogen activation and proton transfer, resulting in the MEA having high self-humidification under conditions of low humidity and high cell temperature.The MEA prepared by inserting a microcrystalline cellulose (MCC) hygroscopic layer between the anode catalyst layer and the gas diffusion layer exhibits high and stable self-humidification performance at cell temperature of 70 °C and 30% relative humidity, the current density at 0.6 V can be up to 1100 mA cm−2 and stable at 1000 mA cm−2 after 24 h continuous running, with the degradation of only 9.1%, which is much better than that of the blank MEA without insertion.

•A dual catalyst layer cathode is designed for water management of ab-PEMFCs.•The cathode is composed of a hydrophilic inner layer and hydrophobic outer layer.•The GDL composition affects the performance of the ab-PEMFC significantly.•The ab-PEMFC with the dual catalyst layer cathode exhibits excellent performance.In an air-breathing proton exchange membrane fuel cell (ab-PEMFC), large amounts of water are generated and condensed on the cathode at high current densities due to the low operating temperature. Water management for ab-PEMFCs remains a challenge. In this paper, a cathode with a dual catalyst layer structure is designed, and the gas diffusion layer (GDL) and microporous layer (MPL) are optimized to improve the water management of an ab-PEMFC. A thin hydrophilic layer using perfluorosulfonate (Nafion) as the catalyst binder is coated on the electrolyte membrane to form an inner layer that maintains a good proton transfer rate, while a hydrophobic outer layer is prepared using a mixture of Nafion and polytetrafluoroethylene as the binder, preventing the removal of water under low-humidity conditions and expelling the excess water generated in the high current density area. A membrane electrode assembly (MEA) with this dual catalyst layer cathode exhibits excellent air-breathing performance, as the MEA's water management is greatly improved by the dual layer structure. We also find that the thickness of the MPL and the hydrophobicity of the GDL significantly affect the air-breathing performance of the MEA, and we attempt to optimize these parameters.

We investigate the performance effects of adding succinic anhydride (SA) to a carbonate-based electrolyte in a high-voltage lithium-ion battery (LIB). The SA significantly improves the electrolyte’s performance, especially its stability, for a 5-V LIB with high-potential LiNi0.5Mn1.5O4 as the cathode material. The oxidation of the carbonate-based electrolyte is strongly inhibited, with the onset potential of oxidation delayed by ca. 0.5 V, as SA has a lower oxidative stability than the carbonate and thus decomposes first. When a sample containing 3 wt% SA is used as the electrolyte for a Li/LiNi0.5Mn1.5O4 half cell, the cell exhibits quite good cycling stability; the capacity fade up to 200 cycles at 1 and 2 C is 90 and 92 %, compared with only 48 and 47 % for a cell containing the standard electrolyte. The electrolyte and cathode are characterized with electrochemical impedance spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy, which demonstrate that a stable protective film is formed on the cathode’s surface in the presence of SA, resulting in the good cycling stability of Li/LiNi0.5Mn1.5O4 half cells at room temperature.

In this work, the effects of the addition of transition metals (Mn, Fe, Co, Ni, Cu) on the structure and performance of the doped carbon catalysts M-PANI/C-Mela are investigated. The results show that the doping of various transition metals affected structures and performances of the catalysts significantly. Doping with Fe and Mn leads to a catalyst with a graphene-like structure, and doping with Co, Ni, and Cu leads to a disordered or nanosheet structure. The doping of transition metals can enhance the performance of the catalysts, and their ORR activity follows the order of Fe > Co > Cu > Mn > Ni, which is consistent with the order of their active N contents. We suggest that the various performance enhancements of the transition metals may be the result of the joint effect of the following three aspects: the N content/active N content, metal residue, and the surface area and pore structure, but not the effect of any single factor.Keywords: doped carbon; effect; oxygen reduction reaction; performance; structure; transition metals

A high-performance doped carbon catalyst with ultrahigh surface area (1123 m2 g−1) and hierarchical porous structures was prepared through an economical, non-template pyrolyzing approach using cross-linked polystyrene, melamine and iron chloride as precursors. The catalyst exhibits excellent oxygen reduction reaction (ORR) performance, outstanding methanol tolerance, remarkable stability, and high catalytic efficiency (nearly 100% selectivity for the four-electron ORR process). Remarkably, its ORR activity can even surpass that of the commercial Pt/C catalyst in alkaline media, with a half-wave potential 20 mV more positive. To the best of our knowledge, it is also one of the most active ORR catalysts in alkaline media to date. By investigating the effects of N dopants and Fe residue on the catalyst's ORR performance, we find that residual Fe is as important as doped nitrogen in enhancing the ORR performance. The catalyst's high ORR performance, outstanding stability and excellent methanol tolerance, combined with its hierarchical porous morphology, make it promising for the application in novel, environmentally friendly electrochemical energy systems. This research also provides a potential way to turn waste into wealth.

A Pt@TNT catalyst with Pt nanoparticles entrapped in titanate nanotubes (TNT) was prepared by hydrophobic modification of the exterior surface of the TNT and impregnation with hexachloroplatinic acid (H2PtCl6) aqueous solution. The catalyst's enhanced activity towards the hydrogenation of phenol (as high as ∼3200 gphenol h−1 gPt−1 of qTOF) can be ascribed to the confinement effect.

High-performance heteroatom-doped carbon catalysts with large surface areas were prepared by pyrolyzing nanorod precursors that had been synthesized by polymerizing a mixture of aniline (An) and β-naphthalene sulfonic acid (NSA). The catalysts were characterized by scanning and transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, N2 adsorption/desorption isotherms, and elemental analysis. We intensively investigated how the catalysts’ structure and catalytic performance were affected by (i) the ratio of NSA to An and (ii) the addition of Fe. The catalysts retained their nanorod morphology after pyrolysis. The optimal NSA/An ratio was 3/2 and the optimal Fe content was 3 wt%. The catalysts showed excellent activity toward oxygen reduction in an acidic medium, with the onset potential, half-wave potential, and limiting current density values reaching 0.86, 0.73 V (vs. reversible hydrogen electrode), and 5.28 mA cm−2, respectively. We suggest that the catalysts’ high performance may be due to the co-doping effects of nitrogen, sulfur, and iron, as well as the large surface area created by the nanorod structures.

Uniform nitrogen and sulfur co-doped carbon nanospheres with an average diameter of approximately 200 nm were prepared using sulfur and polyacrylonitrile as precursors. The materials were characterized using scanning electron microscopy, transmission electron microscopy, elemental analysis, and X-ray photoelectron spectroscopy. The characterization results suggest the as-prepared materials had uniform, porous, nanospherical morphologies and high surface areas. For the typical sample containing 9.5% sulfur, the surface area is up to 653 m2 g−1. The catalysts exhibited enhanced catalytic activity, outstanding long-term stability, and excellent methanol tolerance in an alkaline medium. Significantly, the sulfur addition was found to be vital in improving materials’ catalytic performance through preventing aggregation of the nanospheres, constructing porous structures, increasing the surface area, and participating in the formation of active sites.

•Spinel LiNi0.5Mn1.5O4 materials are synthesized by a two-step approach.•The spinel oxide precursor is derived from the oxalate precipitation.•The materials had capacities of 136 mAh g−1 at C/10 rate and good cycle stability.•The calcining temperature plays an important role for the performance of the materials.A high voltage cathode material, LiNi0.5Mn1.5O4, is synthesized with a two-step approach, in which the nickel–manganese oxalate precipitate is firstly obtained by adding oxalic acid to the solution of nickel and manganese ions precursors, followed by calcining the oxalates to obtain spinel nickel–manganese oxide, incorporating lithium ions with ball milling and calcining at 900 °C for 15 h. The materials are characterized with TG, XRD, SEM, BET and FTIR; it is revealed that both nickel–manganese oxide and final LiNi0.5Mn1.5O4 have well defined spinel structure. The LiNi0.5Mn1.5O4 spinel materials exhibit high capacities and good cyclic stability, the capacity of the materials is in the range from 126 to 136 mAh −1, depending on the calcining temperatures. The sample calcined at an optimal temperature of 900 °C exhibits best performance, the capacity is high up to 136 mAh g−1 at tenth cycle and the capacity retention after 50 cycles is 93%. For the sample prepared by mixing and milling oxalate with lithium salt, the discharge capacity is only 115 mAh g−1. We suggest that the spinel oxide derived from oxalate may play an important role for the high performance and high stability of the final cathode materials.

•Nitrogen doped graphene catalyst is prepared by a facile transfer doping approach.•The nitrogen content of the catalyst is high up to 6.25 at%.•This catalyst shows ORR catalytic activity comparable to Pt/C in alkaline medium.Well defined nitrogen-doped graphene (NG) is prepared by a transfer doping approach, in which the graphene oxide (GO) is deoxidized and nitrogen doped by the vaporized polyaniline, and the GO is prepared by a thermal expansion method from graphite oxide. The content of doped nitrogen in the doped graphene is high up to 6.25 at% by the results of elements analysis, and oxygen content is lowered to 5.17 at%. As a non-precious metal cathode electrocatalyst, the NG catalyst exhibits excellent activity toward the oxygen reduction reaction, as well as excellent tolerance toward methanol. In 0.1 M KOH solution, its onset potential, half-wave potential and limiting current density for the oxygen reduction reaction reach 0.98 V (vs. RHE), 0.87 V (vs. RHE) and 5.38 mA cm−2, respectively, which are comparable to those of commercial 20 wt% Pt/C catalyst. The well defined graphene structure of the catalyst is revealed clearly by HRTEM and Raman spectra. It is suggested that the nitrogen-doping and large surface area of the NG sheets give the main contribution to the high ORR catalytic activity.A nitrogen-doped graphene (NG) catalyst is prepared with a transfer doping approach, in which the graphene oxide (GO) is deoxidized and doped by the polyaniline evaporated from another lower boat containing polyaniline. The graphene oxide is prepared through thermal expansion of graphite oxide. For the catalyst prepared at optimal conditions, the nitrogen content could be high up to 6.25 at%, for the oxygen reduction reaction in alkaline medium, the catalyst exhibited high activity, which is comparable to commercial 20 wt% Pt/C catalyst.

•The particle size of Au could be reduced by the addition of small amount of Pt.•A core–shell catalyst was prepared by a facile pulse electrodeposition method.•The catalyst exhibits excellent activity towards the oxidation of formic acid.A novel core–shell structured AuPt@Pd/C catalyst for the electrooxidation of formic acid is synthesized by a pulse electrodeposition process, and the AuPt core nanoparticles are obtained by a NaBH4 reduction method. The catalyst is characterized with X-ray powder diffraction and transmission electron microscopy, thermogravimetric analysis, cyclic voltammetry, CO stripping and X-ray photoelectron spectroscopy. The core–shell structure of the catalyst is revealed by the increase in particle size resulting from a Pd layer covering the AuPt core, and by a negative shift in the CO stripping peaks. The addition of a small amount of Pt improves the dispersion of Au and results in smaller core particles. The catalyst's activity is evaluated by cyclic voltammetry in formic acid solution. The catalyst shows excellent activity towards the anodic oxidation of formic acid, the mass activity reaches 4.4 A mg−1Pd and 0.83 A mg−1metal, which are 8.5 and 1.6 times that of commercial Pd/C. This enhanced electrocatalytic activity could be ascribed to the good dispersion of Au core particles resulting from the addition of Pt, as well as to the interaction between the Pd shell layer and the Au and Pt in the core nanoparticles.

•A novel biomass-derived carbon catalyst is prepared through pyrolyzing the nori.•The catalyst shows excellent activity and stability toward oxygen reduction.•The addition of melamine improved the performance of the catalyst significantly.A novel biomass-derived, N-doped carbon catalyst for fuel cell cathodes is synthesized using nori as the precursor and melamine as the promoter. The catalyst is characterized using various physicochemical techniques as well as electrochemical analysis. The results show that the catalyst has a graphene-like structure and that its ORR activity is comparable or even superior to that of Johnson Matthey Pt/C catalyst in 0.1 M KOH medium. It also exhibits excellent tolerance to methanol and impressive stability, showing almost no deterioration after 10,000 cyclic voltammetry cycles.A novel biomass-derived N-doped carbon catalyst for fuel cell cathode is synthesized using nori as precursor. The catalyst has graphene-like structure, and exhibits excitingly high ORR activity in an alkaline medium, excellent tolerance to methanol, and impressive stability. Its ORR activity is comparable even superior to that of JM Pt/C catalyst.

•Core–shell Ir@Pt/C catalyst is prepared by pulse electrochemical deposition method.•The catalyst exhibits ultra high Pt dispersion with shell thickness of ca. 1.0 nm.•The oxidation potential of CO on the catalyst is 108 mV lower than that of Pt/C.•The Pt mass activity of the catalyst towards MOR and ORR is enhanced by three times.A novel core–shell structured catalyst, Ir@Pt/C, was prepared by a facile pulse electrochemical deposition approach, demonstrating several times higher mass activity towards both the anodic oxidation of methanol and the cathodic reduction of oxygen than commercial Pt/C catalyst. And the results of CO stripping revealed that the Ir@Pt/C catalyst exhibited greater ease of CO removal. The enhanced performance of the catalyst could be ascribed to the high dispersion of Pt, which led to the higher utilization of Pt, and the synergetic effect of Pt with Ir in the core–shell structure.

•A multielement co-doped reduced graphene oxide is prepared by a one-pot method.•The catalyst exhibits excellent ORR performance superior to the Pt/C catalyst.•The catalyst has a high surface area of 437 m2 g− 1.•The co-doping effect of Fe, N and S is well investigated and demonstrated.A Fe, N and S multielement co-doped reduced graphene oxide (Fe–N–S/rGO) was successfully prepared using a one-pot method by directly pyrolyzing a mixture of graphene oxide (GO), FeCl3, melamine and sulfur in N2 flow, during which deoxidization of GO and multielement co-doping are realized simultaneously. This catalyst shows excellent oxygen reduction activity in an alkaline medium, with an onset potential of 0.95 V (vs. RHE) and a kinetic-limiting current density of 4.78 mA cm− 2 at 0.68 V (vs. RHE), which is superior to that of commercial Pt/C. Furthermore, it exhibits long-term stability, excellent methanol tolerance and high selectivity for the four-electron reduction pathway.

•Self-humidifying membrane electrode assembly is prepared with microcrystalline cellulose.•Excellent performance is obtained under 20% low humility.•The optimal microcrystalline cellulose content for membrane electrode assembly is ca.4 wt.%.•Good self-humidification stability is confirmed by a 22 h long term experiment.A novel self-humidifying membrane electrode assemblies (MEAs) with the addition of microcrystalline cellulose (MCC) as a hygroscopic agent into anode catalyst layer was prepared to improve the performance of proton exchange membrane fuel cell (PEMFC) under low humidity conditions. The MEAs were characterized by SEM, contact angles and water uptake measurements. The MEAs with addition of MCC exhibit excellent self-humidifying single cell performance, the cell temperature for self-humidification running is up to 60 °C. As an optimized MEA with 4 wt.％ MCC in its anode catalyst layer, its current density at 0.6 V could be up to 760 mA cm−2 under 20% of relative humidity, and remains at 680 mA cm−2 after 22 h long time continuous testing, the attenuation of the current density is only 10%. While the current density of the blank MEA without addition of MCC degraded sharply from 300 mA cm−2 to 110 mA cm−2, the attenuation of the current density is high up to 70% within 2 h.

•A novel biomass-derived doped carbon catalyst is prepared using soybean as precursor.•The catalyst exhibited high ORR activity comparable to Pt/C in an alkaline medium.•The addition of ZnCl2 enhanced the surface area and performance of the catalyst.A high-performance doped carbon catalyst with a BET surface area of up to 949 m2 g−1 has been prepared by pyrolyzing soybean biomass with ZnCl2 as an activator, followed by acid leaching with H2SO4 and graphitization. For the cathodic reduction of oxygen, the catalyst exhibits excellent activity in an alkaline medium. Its onset potential and half-wave potential for the oxygen reduction reaction reach −0.02 V and −0.12 V (vs. Ag/AgCl) in 0.1 M KOH, almost comparable to those of commercial 20 wt% Pt/C catalyst. It is found that the addition of zinc chloride can significantly enhance the catalyst's surface area and activity. We suggest that the high performance of this type of catalyst is mainly contributed from its high active center density resulted from the high surface area of the catalyst, which is caused by the activation of zinc chloride.A novel high-performance, biomass-derived, carbon-based catalyst, with a BET surface area of up to 949 m2 g−1, has been prepared for the first time by pyrolyzing soybean biomass impregnated with a chemical activator, followed by acid leaching and graphitization. For the cathodic reduction of oxygen, the catalyst exhibits excellent activity in an alkaline medium, almost comparable to the performance of commercial 20 wt% Pt/C catalyst.

Titanate nanotubes (TNTs) were coupled with amino-propyl-triethoxy silane (KH550) and calcinated at 400 °C, then the silica modified titanate nanotubes (STNTs) were prepared and used as the support of a Pd catalyst by the method of wet-impregnation. The catalyst was characterized with XRD, Raman spectra, TEM, XPS, and H2-TPR/TPD. The silica modification could effectively resist morphology collapse and crystallization of TNT during calcination, and preserve the high surface area of the TNT support, which contribute to the high metal dispersion of loaded Pd. Moreover, the introduced silica could strengthen the metal–support interaction, causing an electronic effect that facilitates the reduction of Pd ions. The Pd/STNT showed 3 times and 2.5 times higher activity than those of commercial Pd/C and unmodified Pd/TNT catalysts towards the selective hydrogenation of cinnamaldehyde at room temperature, respectively, indicating the enhanced catalytic activity by the addition of silica.

•Pd nanospheres are synthesized by a solvothermal method.•Pd@Pt catalyst is prepared by an underpotential deposition process.•The mass activity of Pt of the Pd@Pt nanospheres is 3.3 times higher than that of commercial Pt/C.Pd@Pt nanoparticles with a three-dimensional (3D) nanospherical shape have been prepared using a two-step approach in which the Pd nanospheres are synthesized controllably by a solvothermal method, and then a Pt monolayer is deposited on the Pd nanospheres using an underpotential deposition process. We systematically investigate (i) the influences of temperature and additive on the morphology of the Pd nanoparticles and (ii) the electrochemical activity of Pd@Pt for the oxygen reduction reaction (ORR). The Pd@Pt nanoparticles exhibit enhanced activity towards the ORR. The mass activity of Pt in the Pd@Pt nanospheres (1.03 A mgPt−1) is 3.3 times higher than that of commercial Pt/C (0.24 A mgPt−1). The catalyst enhanced activity may result from the 3D structure of the Pd nanospheres and the monolayer dispersion of Pt on the surface of the nanoparticles.Pd@Pt nanoparticles with a three-dimensional (3D) nanospherical shape have been prepared using a two-step approach in which the Pd nanospheres are synthesized controllably by a solvothermal method, then a Pt monolayer is deposited on the Pd nanospheres using an underpotential deposition process. The Pd@Pt nanoparticles exhibit enhanced activity towards the ORR; the mass activity of Pt in the Pd@Pt nanospheres (1.03 A mgPt−1) is 3.3 times higher than that of commercial Pt/C (0.24 A mgPt−1).

Lithium nickel manganate is recognized as a type of promising cathode material for lithium-ion battery, due to its advantages such as high voltage, high power density, and relative lower cost. In this paper, a series of LiNixMn2 − xO4 cathode materials with various molar ratio of Ni/Mn have been prepared with a co-precipitation method, followed by a solid state reaction, and the effect of the molar ratio of Ni/Mn on the structure and properties of materials are intensively investigated by means of X-ray diffraction (XRD), Fourier transform infrared spectrometer (FTIR), scanning electron microscopy (SEM), and performance measurements, etc. It is revealed that all the samples with x from 0 to 0.5 have well-defined spinel structure and fit well to Fd-3 m space group. With the increase of the molar ratio of Ni/Mn, the diffraction peaks shift to higher angle slightly and the lattice parameter decreases gradually by the XRD results. Furthermore, it is found that the capacity at the 4.0 V plateau decreases while the capacity at 4.7 V plateau increases with the increase of the ratio of Ni/Mn, and the total discharge capacity shows growth trend with the increase of Ni content. It is important that all the samples with various molar ratio of Ni/Mn exhibit good cyclic stability. Based on the experimental results, we suggest that the Ni may incorporate into the lattice of LiMn2O4 substituting of Mn. The plateau at 4.7 V is related to the Ni ions and the plateau at 4.0 V is related to the Mn ions in the materials.

A novel hierarchical nano/microstructure of LiFePO4 microspheres consisting of nanofibers has been synthesized by a solvothermal approach with a mixture of water and 1,2-propanediol as solvent. The influences of temperature and solvent composition on the morphology and electrochemical performance of the products are investigated. The optimum temperature is 140 °C, and the optimum solvent composition is 1:5 for the volume ratio of water to 1,2-propanediol. The initial discharge capacity of the LiFePO4/C microsphere electrode is high and up to 163.9 mA h g−1 and the capacity increased gradually to 164.9 mA h g−1 after 10 cycles, indicating the excellent stability of the materials.

A high-performance, low platinum loading catalyst for the anodic oxidation of methanol, Pd@PtRu/C, is prepared by a two-step colloidal approach. The activity of the Pd@PtRu/C catalyst is 1.67 times and 1.81 times that of PtRu/C and PtRuPd/C catalysts, respectively. The catalysts are characterized by TEM, XPS, and XRD. The active components are dispersed on the surface of the carbon support very well, yielding a particle size of ca. 4.7 nm and a shell thickness of ca. 0.25 nm. The catalyst's high activity may be attributed to the high exposure and dispersion of PtRu, as well as the interaction of PtRu in the shell layer with Pd in the core, resulting from the catalyst's core–shell structure.Graphical abstractA core–shell structured catalyst, Pd@PtRu/C, with PtRu alloy shell was prepared by two stage colloidal method. The catalyst showed superior activity to PtRu/C and PtRuPd/C catalysts for the anodic oxidation of methanol, its activity is 1.67 times and 1.81 times of that of PtRu/C and PtRuPd/C catalysts, respectively. The If/Ib ratio of the catalyst is high up to 1.58, indicating the good poisoning tolerance of the core–shell catalyst with PtRu shell layer.Highlights► Core–shell Pd@PtRu/C catalyst was prepared by a two-step colloidal method. ► The mass activity for Pd@PtRu/C catalyst is about 1.67 times as large as PtRu/C. ► The catalyst shows excellent poisoning tolerance as PtRu/C catalyst. ► The interaction of alloy shell with Pd core was revealed by XPS results.

•A self-humidifying MEA is prepared by adding both PVA and silica to the anode layer.•The MEA shows excellent self-humidification performance at 60 °C and under 15% RH.•Good self-humidification stability is confirmed by a 30 h long term experiment.A novel self-humidifying membrane electrode assembly (MEA) has been successfully prepared by adding both a hydrophilic organic polymer (polyvinyl alcohol, PVA) and an inorganic oxide (silica) to the anode catalyst layer. This MEA shows excellent self-humidification performance under low-humidity conditions. A sample containing 3 wt.% PVA and 3 wt.% silica in the anode catalyst layer achieves a current density as high as 1100 mA cm−2 at 0.6 V, and the highest peak power density is 780 mW cm−2, operating at 60 °C and 15% relative humidity for both anode and cathode. The sample also shows excellent stability at low-humidity: after 30 h of continuous operation under the same conditions, the current density decreases just slightly, from 1100 mA cm−2 to ca. 900 mA cm−2, whereas with MEAs to which only PVA or silica alone had been added, the current densities after 30 h is just 700 mA cm−2 and 800 mA cm−2, respectively. The improved self-humidification performance can be attributed to the synergistic effect of two hygroscopic materials in the anode catalyst layer.The MEA prepared with addition of silica and PVA simultaneously in anode catalyst layer exhibits excellent self-humidification performance at cell temperature of 60 oC under 15% RH both for anode and cathode. Its long term self-humidification performance is much better than those with addition of silica or PVA only, as well as the blank MEA.

•Nitrogen doped carbon catalyst with vesicular structure has been prepared.•The catalyst has the BET surface area of high up to 555 m2 g−1.•Excellent ORR performance closing to Pt/C in acid medium has been achieved.Vesicular nitrogen doped carbon (VNC) material, with BET surface area of high up to 555 m2 g−1, has been prepared by pyrolyzing the polyaniline covering on the Fe2O3 nanoparticles, followed by acid leaching with H2SO4 and graphitization. For the cathodic reduction of oxygen, the catalyst exhibits excellent activity and stability. Its onset potential and half-wave potential for the oxygen reduction reaction reach 0.93 V and 0.82 V (vs. reversible hydrogen electrode) in 0.5 M H2SO4, which are comparable to the performance of commercial 20 wt% Pt/C catalyst. It is demonstrated that the air/hydrogen single cell with VNC as cathode catalyst, has an open-circuit cell potential of 0.85 V and 191 mW cm−2 of maximum power density at cell temperature of 70 °C. It is suggested that the high performance of this type of catalyst results from its high active center density, which may be caused by the high surface area of the vesicular structure of the catalyst. Furthermore, we believe that the ferric oxide may act as the template of the vesicular structure, and the iron may just participate in the construction of active sites, but not as a component of the active site.Vesicular nitrogen doped carbon (VNC) catalyst has been prepared by covering polyaniline on the Fe2O3 nanoparticles, followed by pyrolysis, acid leaching with H2SO4, and graphitization. This catalyst has BET surface area of high up to 555 m2 g−1, and exhibits excellent ORR electrocatalytic activity closing to Pt/C in acid medium, far higher than that of the non-vesicular nitrogen doped carbon catalyst.

Controllable growth of high-quality hybrid nanostructures is highly desirable for the fabrication of hierarchical, complex and multifunctional devices. Here, PdAg alloys have been controllably grown at different locations on gold nanorods, producing dumbbell-like nanostructures with PdAg at the ends of the gold nanorods or branched nanostructures with PdAg grown almost perpendicular to the gold nanorods. The nucleation sites of PdAg alloys on the gold nanorods can be effectively tuned by varying the concentrations of H2PdCl4, AgNO3 and cetyltrimethylammonium bromide (CTAB). The dumbbell-like and branched nanostructures were characterized by transmission electron microscopy (TEM), high-resolution TEM (HRTEM), line-scanning energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and UV-Vis absorption spectroscopy. Their electrocatalytic performance was evaluated using ethanol oxidation as a probe reaction. The dumbbell-like nanostructures show a better anti-poisoning performance, but a worse electrochemical activity than the branched ones. The results provide guidelines for the controlled growth of complicated nanostructures for either fundamental studies or potential applications.

By introducing nickel chemical into the precursor sol of LiFePO4, a series of Ni-doped LiFePO4 composite cathode materials, denoted as LiFe1 − xNixPO4/C (x = 0, 0.01, 0.03, 0.05 and 0.10) were prepared by a spray drying–carbothermal approach. The materials were characterized with X-ray diffraction (XRD), scanning electron microscope (SEM), and electrochemical impedance spectrum etc. It is found that the doping of nickel with appropriate amount caused a slight shift of diffraction peaks towards higher angles and enhanced the dispersion of nanoprimary particles, which could be observed from their XRD patterns and SEM images. For the sample with 3 mol% Ni doing, the charge transfer resistance reduced from 52.4 Ω of LiFePO4 to 18.7 Ω of LiFe0.97Ni0.3PO4/C, and the potential interval of the redox peaks reduced from 0.51 to 0.40 V, indicating the better reversible of Ni-doped materials. For the sample LiFe0.97Ni0.03PO4/C, its initial discharge capacities at various rates are 169.2 (0.2 C), 156.2 (1.0 C), 147.9 (2.0 C), 135.5 (5.0 C), and 94.0 (10.0 C) mAh g−1, respectively, enhanced by 55.2 % (at 5.0 C) and 82.1 % (at 10.0 C) compared with LiFePO4. Furthermore, after 200 cycles of charge/discharge at 0.5 C, the capacity of LiFe0.97Ni0.03PO4/C only decreased 8.8 %, but over 25 % decrease was observed for LiFePO4/C.

Nitrogen-doped carbon nanotube (N-CNT) arrays were prepared by chemical vapor deposition, using ferrocene as the catalyst precursor and imidazole as the carbon and nitrogen precursor. For the reduction of oxygen, the N-CNTs showed excellent electrocatalytic activity in both acidic and alkaline media. The N-CNTs were characterized by scanning and transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and elemental analysis. The samples had a high nitrogen content (8.54 at.%) and a bamboo-like structure, and their activity varied according to the amount of pyridinic nitrogen they contained.

A biocompatible nanovalve attached to the surface of MCM-41 mesoporous nanoparticles is designed to release encapsulated guest molecules controllably under pH activation. This nanovalve system is comprised of α-cyclodextrin (α-CD) rings that encircle p-anisidino linkers, and can be tuned to respond under specific pH conditions through chemical modification of the linkers. One of the distinctive features of this functional nanovalve system lies in its excellent bio-stability and durability in cell culture medium solution, the binding between the α-CD and p-anisidino groups was not interrupted or disintegrated by the proteins in the DMEM solution without adjusting the pH value. Luminescence spectroscopy demonstrates that the on-command pH-activated system displays very good bio-stability—no drug leakage at pH ∼7.4 and excellent drug release performance not only in H2O but also in cell culture medium at pH ∼5.5.Graphical abstractA biocompatible pH-responsive drug delivery nanovalve system was designed, synthesized, and tested. The on-command pH-activated system displayed very good stability—no drug leakage at pH ∼7.4 and excellent drug release performance not only in H2O but also in cell culture medium at pH ∼5.5.Highlights► A biocompatible pH-responsive nanovalve was designed based on MCM-41 mesoporous nanoparticles. ► The nanoparticles possess uniform small size and good monodispersion. ► The on-command pH-activated system displays very good bio-stability. ► No drug leakage was observed in cell culture medium solution before the pH was tuned. ► The nanovalve system exhibits excellent drug release performance not only in H2O but also in cell culture medium at pH ∼5.5.

In this work, a novel self-humidifying membrane electrode assembly (MEA) with addition of polyvinyl alcohol (PVA) as the hygroscopic agent into anode catalyst layer was developed for proton exchange membrane fuel cell (PEMFC). The MEA shows good self humidification performance, for the sample with PVA addition of 5 wt.% (MEA PVA5), the maximum power density can reach up to 623.3 mW·cm−2, with current densities of 1000 mA·cm−2 at 0.6 V and 600 mA·cm−2 at 0.7 V respectively, at 50 °C and 34% of relative humidity (RH). It is interesting that the performance of MEA PVA5 hardly changes even if the relative humidity of both the anode and cathode decreased from 100% to 34%. The MEA PVA5 also shows good stability at low humidity operating conditions: keeping the MEA discharged at constant voltage of 0.6 V for 60 h at 34% of RH, the attenuation of the current density is less than 10%, whilst for the MEA without addition of PVA, the attenuation is high up to 80% within 5 h.Highlights► A self-humidifying MEA is firstly prepared by adding PVA in anode catalyst layer. ► The MEA still shows excellent performance even if the RHs are lower down to 34%. ► Good self-humidification stability is confirmed by a 60 h long term experiment.

PdPt bimetallic catalysts that employ CeO2-modified carbon black as a support have been prepared using an organic colloidal method. PdPt/CeO2-C shows excellent performance toward the anodic oxidation of formic acid. The effects of varying both Pd to Pt ratio and CeO2 content have been investigated. The optimal Pd to Pt atomic ratio is 15, indicating that addition of small amounts of Pt can significantly enhance the activity of the catalyst. When the CeO2 content in the catalyst reaches as high as ∼15 wt.%, the catalyst shows the maximum activity. Adding CeO2 not only enhances the catalytic activity of the material, but may also change the mechanism of its catalysis of the anodic oxidation of formic acid. Pd15Pt1/15CeO2-C exhibited 60% higher activity than Pd/C, and had a negative shift in onset potential of more than 0.1 V. Based on characterization by X-ray diffraction, X-ray photoelectron spectroscopy, thermogravimetric analysis and transmission electron microscopy, the interactions between the components are revealed and discussed in detail.

The direct ethanol fuel cell has been attracting increased attention due to its safety and the wider availability of ethanol as compared with methanol. The present work investigates the anodic oxidation of ethanol on a core-shell structured Ru@PtPd/C catalyst in alkaline media. The catalyst shows high activity toward the anodic oxidation of ethanol; with 18 wt.% ruthenium as the core and 12 wt.% PtPd (Pt:Pd = 1:0.2) as the active shell, its activity in terms of PtPd loading is 1.3, 3, 1.4, and 2.0 times as high as that of PtPd/C, PtRu/C, Pd/C, and Pt/C, respectively, indicating high utilization of Pt and Pd. The ratio of forward peak current density to backward peak current density (If/Ib) reaches 1.5, which is 1.9 times that of PtPd/C catalyst, revealing high poisoning tolerance to the intermediates in ethanol electrooxidation. In addition, the stability of Ru@PtPd/C is higher than that of Pt/C and PtPd/C, as evidenced by chronoamperometric evaluations. The catalyst is extensively characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy. The core-shell structure of the catalyst is revealed by XRD and TEM.Highlights► Core-shell structured Ru@PtPd catalyst prepared by a two-stage procedure. ► High activity towards ethanol electrooxidaiton in alkaline media. ► High poisoning tolerance to the intermediates. ► Higher stability than that of Pt/C, Pd/C and PtPd/C.

Small nanoparticles offer high surface areas and are certainly desirable for electrocatalytic reactions and fuel cells. However, the drawback of using small nanoparticles is their tendency towards particle aggregation. This paper aims to inhibit platinum agglomeration by adding silicon oxide to a carbon support for enhanced catalytic activity in low-temperature fuel cells. The catalysts are characterized by X-ray diffraction and transmission electron microscopy. Physical characterization and cyclic voltammetry techniques at room temperature are used to assess the effects of silicon oxide amount, post-heating temperature, and holding time on particle size and dispersion of active components, and the catalysts’ activity towards the methanol oxidation and oxygen reduction reactions. It is found that using a support of carbon powder with 3 wt.% silicon oxide can enhance the electrochemically active surface area of Pt catalysts and their activity towards the anodic oxidation of methanol and reduction of oxygen. The active components are also more resistant than Pt/C to agglomeration upon heating.

A miniature air-breathing direct formic acid fuel cell (DFAFC) based 4-cell stack, with a gold coated printed circuit board as the end plate and current collector, and with an independent fuel reservoir to avoid undesired interlaced electrolysis between different cells, is designed and investigated. Emphasis in the investigation is placed on design details, cell performance, dynamic response, and the stability of both the stack and individual cells. The striking difference in our cell configuration as compared with constructions reported in the literature is the existence of independent cavities as fuel reservoirs for each single cell. The outstanding merit of this particular design is the avoidance of water hydrolysis between electrodes, which is inevitable in stacks built with a shared fuel tank. A maximum power density of 56.6 mW cm−2 is achieved and 5.0 M is considered as the optimum concentration for this 4-cell stack. A single cell can discharge at 20 mA for 70 h with a voltage decline rate of only 2.7 mV h−1 while sufficient formic acid is pumped into the cell.

Sponge-like mesoporous silica (SMS) was prepared using a gelatin-assisted templating route with dodecyl amine (DDA) as the main template. The synthesized SMS showed a bimodal pore size distribution, with mesopores of 3.2 nm and texture pores of 50–80 nm. We found that gelatin (GE) had a pronounced effect on the morphology and porosity of the synthesized silica, which was then extensively investigated by electron microscopy. When the mass ratio of GE to DDA, MGE/MDDA, was increased from 0.05 to 0.6, the morphology evolved from a sponge-like sphere to a hollow sphere, and finally to a popcorn-like hollow sphere. It was also found that the porosity could be modulated by changing the GE concentration. Due to its unique bimodal porosity, the synthesized SMS demonstrated a higher adsorption capacity and faster lysozyme adsorption rate, making SMS potentially applicable in the immobilization of enzymes with high capacity and bio-activity.Graphical abstractSponge-like mesoporous silica (SMS), with bimodal pore size of 3.2 nm and texture pores of 50–80 nm was sythesized using a gelatin-assisted templating route with dode- cyl amine (DDA) as the main template. The material demonstrated a higher adsorption capacity and faster lysozyme adsorption rate, making it potentially applicable in the immobilization of enzymes with high capacity and bio-activity..Highlights► Naturally occurring polymer (gelatin) as assisted template. ► Sponge like silica with bimodal porosity. ► High lysozyme adsorption capacity.

A palladium decorated Pt/C catalyst, Pt@Pd/C, is prepared by a colloidal approach with a small amount of platinum as core. It is found that the catalyst shows excellent activity towards anodic oxidation of formic acid at room temperature and its activity is 60% higher than that of Pd/C. Decoration of palladium shell on the platinum core is supported by XPS results. Due to the use of platinum as core, active components are dispersed very well and the particle sizes are smaller than those of Pd/C. The cyclic voltammetry measurement clearly shows synthetic electro-oxidation effects of formic acid on Pt@Pd/C. It is speculated that the high performance of Pt@Pd/C may result from the unique core–shell structure and synergistic effect of Pt and Pd at the interface. The preparation method for Pt@Pd/C reported in this work will provide additional options for the design of catalysts for direct formic acid fuel cell (DFAFC).

Membrane electrode assemblies (MEAs) with ultra-low platinum loadings are attracting significant attention as one method of reducing the quantity of precious metal in polymer electrolyte membrane fuel cells (PEMFCs) and thereby decreasing their cost, one of the key obstacles to the commercialization of PEMFCs. In the present work, high-performance MEAs with ultra-low platinum loadings are developed using a novel catalyst-sprayed membrane technique. The platinum loadings of the anode and cathode are lowered to 0.04 and 0.12 mg cm−2, respectively, but still yield a high performance of 0.7 A cm−2 at 0.7 V. The influence of Nafion content, cell temperature, and back pressures of the reactant gases are investigated. The optimal Nafion content in the catalyst layer is ca. 25 wt.%. This is significantly lower than for low platinum loading MEAs prepared by other methods, indicating ample interfacial contact between the catalyst layer and membrane in our prepared MEAs. Scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS) measurements reveal that our prepared MEA has very thin anode and cathode catalyst layers that come in close contact with the membrane, resulting in a MEA with low resistance and reduced mass transport limitations.

Conventional double catalyst layer (DCL) structures show no obvious improvement in cathode performance, due to the contradiction between improving mass transfer and maintaining good platinum (Pt) utilization. To decrease this conflict, a novel DCL cathode is prepared using catalysts with two different amounts of Pt; the catalyst with higher Pt content is used in the inner layer to concentrate the Pt, and the catalyst containing less Pt is used in the outer layer to maintain a suitable layer thickness. Polarization characteristics of cathodes with this novel DCL, a conventional DCL, and a single catalyst layer (SCL) are evaluated at ambient pressure in an H2/air PEMFC. The results show a significant increase in performance with the novel DCL cathode. Compared with the SCL cathode, the current density of the novel DCL cathode at 0.6 V increases by 35.9%, while that of the conventional DCL cathode increases by just 8.8%.

In this work, a novel self-humidifying membrane electrode assembly (MEA) with Pt/SiO2/C as anode catalyst was developed to improve the performance of proton exchange membrane fuel cell (PEMFC) operating at low humidity conditions. The characteristics of the composite catalysts were investigated by XRD, TEM and water uptake measurement. The optimal performance of the MEA was obtained with the 10 wt.% of silica in the composite catalyst by single cell tests under both high and low humidity conditions. The low humidity performance of the novel self-humidifying MEA was evaluated in a H2/air PEMFC at ambient pressure under different relative humidity (RH) and cell temperature conditions. The results show that the MEA performance was hardly changed even if the RHs of both the anode and cathode decreased from 100% to 28%. However, the low humidity performance of the MEA was quite susceptible to the cell temperature, which decreased steeply as the cell temperature increased. At a cell temperature of 50 °C, the MEA shows good stability for low humidity operating: the current density remained at 0.65 A cm−2 at a usual work voltage of 0.6 V without any degradation after 120 h operation under 28% RH for both the anode and cathode.

An ultra-low platinum loading membrane electrode assembly (MEA) with a novel double catalyst layer (DCL) structure was prepared by using two layers of platinum catalysts with different loadings. The inner layer consisted of a high loading platinum catalyst and high Nafion content for keeping good platinum utilization efficiency and the outer layer contained a low loading platinum catalyst with low Nafion content for obtaining a proper thickness thereby enhancing mass transfer in the catalyst layers. Polarization characteristics of MEAs with novel DCL, conventional DCL and single catalyst layer (SCL) were evaluated in a H2–air single cell system. The results show that the performance of the novel DCL MEA is improved substantially, particularly at high current densities. Although the platinum loadings of the anode and cathode are as low as 0.04 and 0.12 mg cm−2 respectively, the current density of the novel DCL MEA still reached 0.73 A cm−2 at a working voltage of 0.65 V, comparable to that of the SCL MEA. In addition, the maximum power density of the novel DCL MEA reached 0.66 W cm−2 at 1.3 A cm−2 and 0.51 V, 11.9% higher than that of the SCL MEA, indicative of improved mass transfer for the novel MEA. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) tests revealed that the novel DCL MEA possesses an efficient electrochemical active layer and good platinum utilization efficiency.

In this work, a membrane electrode assembly (MEA) for proton exchange membrane fuel cell (PEMFC) operating under no external humidification has been successfully fabricated by using a composite Pt/SiO2/C catalyst at the anode. In the composite catalyst, amorphous silica, which originated from the hydrolysis of tetraethyl orthosilicate (TEOS), was immobilized on the surface of carbon powder to enhance the stability of silica and provide a well-humidified surrounding for proton transport in the catalyst layer. The characteristics of silica in the composite catalyst were investigated by XRD, SEM and XPS analysis. The single cell tests showed that the performance of the novel MEA was comparable to MEAs prepared using a standard commercial Pt/C catalyst with 100% external humidification, when both were operated on hydrogen and air. However, in the absence of humidification, the MEA using Pt/SiO2/C catalyst at the anode continued to show excellent performance, while the performance of the MEA containing only the Pt/C catalyst rapidly decayed. Long-term testing for 80 h further confirmed the high performance of the non-humidified MEA prepared with the composite catalyst. Based on the experimental data, a possible self-humidifying mechanism was proposed.

In this paper, we report a one-step solution-phase approach to synthesize hexagonal close-packed (hcp) phase Co thin film composed of Co nanosheets generated by chemical reduction of Co2+–EDTA complexes under an external magnetic field. The as-prepared Co film was characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and superconducting quantum interference device (SQUID) magnetometer. The effects of synthetic conditions, such as solvents, reaction temperature and intensity of the magnetic field, on the morphology of the final products were investigated. The coercivity of the as-prepared Co thin film measured in the directions parallel and perpendicular to the film plane reached 321.7 Oe and 220.5 Oe, respectively, which was much higher than that of the bulk Co counterpart. The facile magnetic-field-assisted solution-phase route presented here may provide a new method to prepare magnetic thin film composed of magnetic nanocrystals with anisotropic shapes.

A core–shell structured low-Pt catalyst, PdPt@Pt/C, with high performance towards both methanol anodic oxidation and oxygen cathodic reduction, as well as in a single hydrogen/air fuel cell, is prepared by a novel two-step colloidal approach. For the anodic oxidation of methanol, the catalyst shows three times higher activity than commercial Tanaka 50 wt% Pt/C catalyst; furthermore, the ratio of forward current If to backward current Ib is high up to 1.04, whereas for general platinum catalysts the ratio is only ca. 0.70, indicating that this PdPt@Pt/C catalyst has high activity towards methanol anodic oxidation and good tolerance to the intermediates of methanol oxidation. The catalyst is characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The core–shell structure of the catalyst is revealed by XRD and TEM, and is also supported by underpotential deposition of hydrogen (UPDH). The high performance of the PdPt@Pt/C catalyst may make it a promising and competitive low-Pt catalyst for hydrogen fueled polymer electrolyte membrane fuel cell (PEMFC) or direct methanol fuel cell (DMFC) applications.

A new type of CsHSO4–HZSM-5 inorganic composite electrolyte membrane is prepared by mechanically mixing CsHSO4 (CHS) and nanometer-scale HZSM-5 zeolite powders. The effects of HZSM-5 on the crystallite structure, proton conductivity, and thermal stability of the CsHSO4 electrolyte are investigated. Incorporation of HZSM-5 is found to significantly increase the low-temperature proton conductivity of the CsHSO4 electrolyte, extending its operating temperature down to 100 °C. The composite electrolyte with 40 mol% HZSM-5 shows the highest proton conductivity in the measured temperature range. The low-temperature activation energy of the composite with 40 mol% HZSM-5 is lower than that of the CHS–SiO2 composite. The improvement of the proton conductivity can be attributed to the enhanced interfacial interaction between the two phases. And the small HZSM-5 particles lead to a change in the bulk properties of the ionic salts. The melting point of the CHS–HZSM-5 composite electrolyte is lower than that of the pure CHS electrolyte. The CHS–HZSM-5 composite electrolyte is suitable for polymer electrolyte membrane fuel cells operated at 100–200 °C.

By using two non-ionic surfactants, 1,12-diaminododecane and a triblock copolymer surfactant F127, as templates, grape-like solid spheres of super-microporous silica (SMS) with ordered, worm-like pore structures have been successfully synthesized, then characterized by SEM/TEM, XRD, TG/DTA, etc. In a sample synthesized at 70 °C, well-formed grape-like spheres with worm-like pores were observed by SEM and TEM. The average pore size is ca. 1.87 nm and the specific surface area of the spheres is 865 m2/g. The hydrogen storage capacity of the sample Pd/SMS-70-C, prepared by supporting 5 wt% palladium on SMS (synthesized at 70 °C), is up to 2.56 wt% at 1.2 MPa hydrogen pressure.

Polyphosphazenes are considered to be more useful as proton-conducting membranes than Nafion due to their low methanol permeability, low water swelling ratios, satisfactory mechanical properties, and conductivities comparable to those of Nafion. In this work, compounds 1–6, six polyphosphazenes with different side groups, were designed and calculated. Structural parameters, proton affinities and water adsorptions were obtained on the basis of the optimized geometrical structures. Our calculations were in agreement with experimental results. It was found that the proton conductivities of the sulfonated poly[(aryloxy)phosphazenes] (R1SO3H) are higher than those of the phosphonated ones (R1PO3H2), while the phosphonated poly[(aryloxy)phosphazenes] will retain water better at higher temperature than the sulfonated ones. The electron-withdrawing substituent of R2 is beneficial to proton conductivities and water adsorptions of both sulfonated and phosphonated poly[(aryloxy)phosphazenes].

A novel approach is proposed to prepare ordered hierarchical mesoporous TiO2 by using yeast cells as the template via biomimetic mineralization. The structure and the mophology were characterized by atomic force microscopy (AFM), X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDX), Raman spectra, high-resolution transmission electron microscopy (HRTEM), and N2 adsorption–desorption isotherms (NADI). The bio-templated TiO2 has a hierarchical pore structure mainly distributed at 4.7 nm and 11.3 nm. An air electrode fabricated using this hierarchical mesoporous TiO2 exhibited remarkable electrocatalytic activity for oxygen reduction reaction (ORR). Compared to the electrolytic manganese dioxide (EMD) air electrode employed commercially, a 90% higher catalytic reduction current was achieved for this mesoporous TiO2 electrode. It is supposed that the hierarchically mesoporous structure and ordered pore distribution play important roles in significantly reducing electrochemical polarization and improving mass transport of the air diffusion electrode. This simple and efficient approach could spread as a general way to prepare advanced mesoporous materials in mild condition.

Nano-sized cobalt particles with the diameter of 2 nm were prepared via an organic colloidal process with sodium formate, ethylene glycol and sodium citrate as the reducing agent, the solvent and the complexing agent, respectively. The effects of sodium citrate on the yield, crystal structure, particle size and size distribution of the prepared nano-sized cobalt particles were then investigated. The results show that the average particle diameter decreases from 200 nm to 2 nm when the molar ratio of sodium citrate to cobalt chloride changes from 0 to 6. Furthermore, sodium citrate plays a crucial role in the controlling of size distribution of the nano-sized particles. The size distribution of the particle without sodium citrate addition is in range from tens of nanometers to 300 or 400 nm, while that with sodium citrate addition is limited in the range of (2±0.25) nm. Moreover, it is found that the addition of sodium citrate as a complex agent could decrease the yield of the nano-sized cobalt particle.

Some metal oxides modified with sulfate ions form highly acidic or superacidic catalysts. SO2−4/MxOy solid superacid catalysts, play a vital role in more and more fields such as organic synthesis, fine chemicals, pharmaceuticals, and means for strengthening environmental safeguards. This review highlights the recent development of solid superacid catalysts based on SO2−4/MxOy, including synthesis method, characterization of acid sites and acid strength, and applications.

Two novel catalysts for anode oxidation of formic acid, Pd2Co/C and Pd4Co2Ir/C, were prepared by an organic colloid method with sodium citrate as a complexing agent. These two catalysts showed better performance towards the anodic oxidation of formic acid than Pd/C catalyst and commercial Pt/C catalyst. Compared with Pd/C catalyst, potentials of the anodic peak of formic acid at the Pd2Co/C and Pd4Co2Ir/C catalyst electrodes shifted towards negative value by 140 and 50 mV, respectively, meanwhile showed higher current densities. At potential of 0.05 V (vs. SCE), the current density for Pd4Co2Ir/C catalyst is as high as up to 13.7 mA cm−2, which is twice of that for Pd/C catalyst, and six times of that for commercial Pt/C catalyst. The alloy catalysts were nanostructured with a diameter of ca. 3–5 nm and well dispersed on carbon according to X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements. The composition of alloy catalysts was analyzed by energy dispersive X-ray analysis (EDX). Pd4Co2Ir/C catalyst showed the highest activity and best stability making it the best potential candidate for application in a direct formic acid fuel cell (DFAFC).

Novel ternary palladium based alloy catalysts, PdFeIr/C, for oxygen reduction reaction (ORR) have been successfully prepared via an organic colloid method with ethylene glycol as solvent and sodium citrate as complexing agent. The catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy dispersive X-ray analysis (EDX). Electrochemical activity of the catalysts for ORR was evaluated by steady state polarization measurements, which were carried out on an ultra thin layer rotating disk electrode (RDE). Compared to pure Pd/C and Pd3Fe/C, results showed that the ORR activity of PdFeIr/C was highest, and its methanol tolerance was better than Pt/C catalyst.

A hollow sphere neodymium embedded mesoporous silica material (NEMS) has been synthesized successfully by using neutral 1,12-diaminododecane as template and embedding Nd into the framework simultaneously. It is interesting that a lamellar structured material with MSU-V structure was obtained if only DADD was used as template without embedding of Nd. The synthesized materials were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), BET method, thermal gravimetry/differential thermal analysis (TG/DTA), and X-ray photoelectron spectroscopy (XPS). The hollow sphere morphology was observed by TEM images and clearly revealed the structure of NEMS molecular sieves. Both XRD and XPS results confirmed that the Nd atoms were incorporated into the framework of mesoporous materials. The TG/DTA results verified the good thermal stability of the synthesized NEMS material. The surface area of samples with Si/Nd molar ratio from 10 to 60 reached from 543 to 1103 m2 g−1, respectively. It also found that the Nd embedded mesoporous silica material showed good catalytic activity and selectivity towards the oxidation of styrene, proportional to the neodymium content in the catalysts.

Ultrafine Co nanoparticles with the size of ca. 2 nm were prepared by an organic colloid method, in which sodium formate acted as reducing agent, ethylene glycol acted as solvent, sodium citrate acted as both complexing agent and stabilizing agent, respectively. X-ray diffraction (XRD) analysis indicated that the as-prepared Co nanoparticles were in hexagonal close-packed phase, and transmission electron microscope (TEM) images revealed that the size of the well-dispersed Co nanoparticles was as small as 2 nm, and the sizes were distributed in a very narrow region. The hysteresis loop of the as-prepared Co sample measured at room temperature showed a superparamagnetic behavior due to the extremely small size of the products. It was revealed that sodium citrate played a crucial role in decreasing the particle size and narrowing the size distribution.

Pt–Se/C catalyst for oxygen reduction reaction (ORR) was prepared by a modified organic colloid method with sodium citrate and triphenyl phosphine as complexing agents. The active components were highly dispersed on the carbon black support. The addition of Se improved the dispersion of platinum significantly and reduced the particle size to be less than 1.8 nm. The catalyst showed similar activity compared to Pt/C catalyst, and had a higher tolerance to methanol than Pt/C catalyst. The catalyst was characterized with X-ray diffraction (XRD) and transmission electron microscope (TEM). Electrochemical measurements showed that the synthesized Pt–Se/C catalyst had a four-electron transfer mechanism for oxygen reduction.

PtMoSi/C nanocatalysts were prepared by chemical reduction using formaldehyde, H2, and hydrazine as reducing agents, respectively. The nanocomposites were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). XRD patterns showed a face-centered cubic crystal structure, and TEM images indicated that the nanoparticles that were uniformly dispersed on carbon were 3-4 nm in diameter. XPS analysis revealed that the catalysts contained mostly Pt(0), Mo(VI), and Si(IV). The effects of preparation methods and additives on the catalytic activity were then studied by linear sweep voltammetry (LSV) and cyclic voltammetry (CV). It was found that the PtMoSi/C nanocatalysts (nPt:nMo=3:1 was the optimal ratio of Pt to Mo) prepared using formaldehyde as reducing agent showed higher electrocatalytic activity and better tolerance to poisoning species in methanol oxidation than the homemade PtRu/C and the commercial E-TEK PtRu/C catalysts, and this could be ascribed to the high dispersion of Pt nanoparticles on the carbon by the addition of silicomolybdic acid.

Zirconium embedded MSU-V materials (Zr-MSU-V) have been synthesized using neutral 1,12-diaminododecane as template and zirconyl chloride as precursor. The materials were characterized by X-ray diffraction (XRD), BET method, transmission electron microscopy (TEM), FT-IR, X-ray photoelectron spectroscopy (XPS), UV–vis and thermal gravimetry/differential thermal analysis (TG/DTA). The XRD results showed that the Zr-MSU-V materials retained their structural integrity even when the molar ratio of Si to Zr was up to 10. The surface area of samples with Si/Zr ratio of 10 reached 658 m2/g, and the well-ordered structure of Zr-MSU-V was observed by TEM. FT-IR, XPS and diffuse reflection UV–vis (DR UV–vis) studies confirmed that the Zr atoms were completely incorporated into the mesoporous structure. The thermal stability of the as-synthesized materials was verified using TG/DTA analysis. The Zr-MSU-V materials also showed good hydrothermal stability, and the structure was retained even after boiling in water for 48 h. It was found that the Zr embedded MSU-V materials showed good catalytic activity and selectivity towards the oxidation of styrene, proportional to the zirconium content in the catalysts.

A novel binary oxide photocatalyst ZnO/TiO2 was prepared by a new modified sol–gel method using citric acid as a complex reagent and its photocatalytic activity was investigated. The factors, such as the ratio of amount of doped zinc ion, the precursors, and the calcination temperature on the activities of ZnO/TiO2 photocatalyst, were investigated. SO42−/ZnO/TiO2 was prepared by sulfating the dry gels of ZnO/TiO2 with H2SO4 solution. It was showed that the addition of ZnO could enhance the activity significantly, and sulfating ZnO/TiO2 with sulfuric acid resulted to dramatic enhancement, the degradation ratio of methyl orange could be up to 71.9%, compared with 55% of degradation of ZnO/TiO2 catalyst.

A high-performance bimetallic catalyst with mesoporous silica nanoparticles as support, PdAu/MSN, was prepared by an organic impregnation–hydrogen reduction approach. A series of investigations were conducted to assess the effects of (i) the porous nanoparticle support on the dispersion of active components and on the catalyst’s performance, (ii) the addition of gold on the dispersion of active components and the catalyst’s activity, and (iii) the preparation parameters, such as solvent, pressure, and temperature, on the catalyst’s activity. The active metallic components were highly dispersed, with particle size 2.5 nm. The addition of gold to the catalyst favorably promoted the hydrogenation of cinnamaldehyde. The activity of PdAu0.2/MSN (with Au/Pd molar ratio 0.2:1) was up to four times higher than that of Pd/MSN (without Au as a promoter) and eight times higher than that of commercial Pd/C catalyst. The enhanced activity of PdAu0.2/MSN can be attributed to the synergistic effect of Pd with the added Au and the highly dispersed active components. The ultrahigh activity, as well as its novel structure with controllable compositions, makes this catalyst very attractive for both fundamental research and practical applications.A high-performance bimetallic catalyst with mesoporous silica nanoparticles as support, PdAu/MSN, was prepared successfully. For the hydrogenation of cinnamaldehyde, the activity of PdAu0.2/MSN (with a Au/Pd molar ratio of 0.2:1) was up to four times and eight times higher than that of Pd/MSN and commercial Pd/C catalysts, respectively. The enhanced activity of PdAu0.2/MSN is attributable to the synergistic effect of Pd with added Au and the high dispersion of its active components, which may result from the high surface area of MSN nanoparticles, and mostly the addition of gold.Download high-res image (243KB)Download full-size image

We report a high performance supported Pt catalyst, in which a perfluorosulfonic acid (Nafion) functionalized carbon black is used as support. The catalyst is characterized by infrared spectroscopy (IR), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The TEM image shows that the active Pt component is in nanoparticles and highly dispersed on the carbon black with an average particle size of 1.9 nm. The catalyst shows improved activity towards the methanol anodic oxidation and oxygen reduction reaction (ORR), resulting from the high dispersion of active Pt component. It leads to increases in electrochemically accessible surface areas and ion channels, as well as easier charge-transfer at polymer/electrolyte interfaces. The high platinum utilization and high performance of Pt/Nafion-C catalyst make it a promising electrocatalyst for fuel cell application.

Transition metal nitrides have recently attracted significant interest as electrocatalysts for the oxygen reduction reaction (ORR) owing to their low electrical resistance and good corrosion resistance. In this paper, we describe the preparation of a Nb-based binary nitride material with a porous nanogrid morphology/structure. The catalyst exhibited good catalytic activity and high stability towards oxygen reduction. We also intensively investigated the effect that doping with a second transition metal had on the performance of the catalyst. We found that the ORR activity of NbN could be enhanced significantly by enriching the d electrons of Nb through doping with a second transition metal, and that doping with cobalt resulted in the best improvement. Our optimal catalyst, Nb0.95Co0.05N, had an ORR activity ∼4.6 times that of NbN (current density @ 0.6 V vs. the RHE). XPS results revealed that Co doping increased the proportion of Nb in a low-valence state, which may be one of the most important reasons for the enhanced performance. Another important reason is the high surface area resulting from the porous nanogrid morphology. As transition metal doping is an attractive way to enhance the activity of nitride catalysts, our work may provide an effective pathway to achieve this.

Developing high-performance bifunctional electrocatalysts for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) using nonprecious metal-based catalysts is a major challenge for achieving the commercial success of regenerative fuel cells and rechargeable metal–air batteries. In the present study, we designed a new type of bifunctional catalyst by embedding cobalt sulfide hollow nanospheres in nitrogen and sulfur co-doped graphene nanoholes (Co1−xS/N–S–G) via a simple, one-pot pyrolysis method. The catalyst had a high specific surface area (390.6 m2 g−1) with a hierarchical meso–macroporous structure. In an alkaline medium, the catalyst exhibited high ORR catalytic activity, with a half-wave potential 30 mV more positive and a diffusion-limiting current density 15% higher than a commercial Pt/C catalyst, and the catalyst is also highly active for OER with a small overpotential of 371 mV for 10 mA cm−2 current density. Its overall oxygen electrode activity parameter (ΔE) is 0.760 V, which is smaller than that of Pt/C and most of the non-precious metal catalysts in previous studies. Furthermore, it demonstrated better durability towards both the ORR and OER. Detailed investigation clarified that the material's excellent electrocatalytic performance is attributable to: (1) a synergistic effect, induced by the presence of multiple types of active sites, including cobalt sulfide hollow nanospheres, nitrogen and sulfur dopants, and possible Co–N–C sites; (2) cobalt sulfide hollow nanospheres penetrating through the plane of graphene sheets form strong interaction between them; (3) more edge defects associated with the existence of nanoholes on the graphene basal plane; and (4) the high surface area and efficient mass transfer arising from the hierarchical porous structure.

We report a composite catalyst in which binary transition metal nitride nanoparticles (NPs) were mounted on nitrogen-doped reduced graphene oxide (TiCoNx/N-rGO). The catalyst exhibited outstanding oxygen reduction activity in an alkaline medium. In its optimal form, our catalyst yielded a half-wave potential of 0.902 V (vs. RHE), ∼30 mV more positive than that of the commercial Pt/C catalyst, and its current density at 0.9 V (vs. RHE) reached 2.51 mA cm−2. The ORR activity of our transition metal nitride-mounted N-rGO was much higher than the activities of transition metal nitride alone or N-rGO alone, revealing a strong synergistic effect between the two materials. Further, the catalyst mounted with Ti and Co binary NPs exhibited higher ORR activity than the catalyst mounted solely with Ti nitride NPs, indicating the significant improvement gained by the addition of cobalt. XPS analysis results showed that the mounting of transition metal nitride clearly changed the amount and distribution of N species in the catalyst, causing the percentage of active pyridinic-N species to increase significantly. Moreover, changes in the binding energies of C and Ti atoms proved the synergy between TiCoNx NPs and N-rGO. We therefore ascribe the superior electrochemical activity of our TiCoNx/N-rGO catalyst to this synergy and to the improvement resulting from the addition of Co. In addition to its outstanding ORR activity, this catalyst also showed excellent stability and methanol tolerance, making it a promising Pt-free ORR catalyst for alkaline H2/O2 fuel cells and direct methanol fuel cells.

Developing highly efficient and low-cost electrocatalysts for the oxygen reduction reaction (ORR) to substitute precious Pt-based catalysts is highly important for the commercialization of advanced electrochemical energy conversion systems. Doped carbons have attracted wide attention and have become one of the hottest topics in new energy fields due to their high ORR performance and low cost. In this work, uniform nitrogen and sulphur co-doped hollow carbon nanospheres with an ultra-high surface area (1060 m2 g−1) were fabricated by using polyacrylonitrile and sulphur as the precursors. The catalyst exhibits outstanding ORR performance, excellent stability, methanol tolerance, as well as high selectivity toward the four-electron catalytic pathway. By analyzing the effects of sulphur addition, we found that the sulphur addition is crucial for the formation of uniform nanospherical morphologies, as well as highly porous structures and high surface areas. Besides, sulphur addition was also found to be able to modify the catalysts' atomic compositions effectively by increasing the total and pyridinic N contents while reducing oxidized N contents. Sulphur addition induced unique features in the catalysts' structures and compositions. We believe that this should be the main origins of our catalyst's outstanding ORR performance.

A Pt@TNT catalyst with Pt nanoparticles entrapped in titanate nanotubes (TNT) was prepared by hydrophobic modification of the exterior surface of the TNT and impregnation with hexachloroplatinic acid (H2PtCl6) aqueous solution. The catalyst's enhanced activity towards the hydrogenation of phenol (as high as ∼3200 gphenol h−1 gPt−1 of qTOF) can be ascribed to the confinement effect.

Three-dimensional palladium nanoflowers (Pd-NF) composed of ultrathin Pd nanosheets were synthesized by a solvothermal approach. The Pd-NF catalyst shows 6.6- and 5.5-fold enhancements in mass activity and surface activity compared to normal palladium nanoparticles (Pd-NP) in the electro-oxidation of formic acid.

A novel high-performance air cathode was prepared by synthesizing Co3O4 nanowire clusters on a nickel foam (NF) substrate and then decorating these clusters with Pd nanoparticles using a pulse electrodeposition method. This carbon-free and binder-free cathode had a well-defined, flower-like morphology, presenting clusters composed of nanowires with a diameter of ∼60 nm and a length of ∼5 μm on which were located Pd particles as small as 10 nm. The new cathode exhibited excellent low polarization and superior cycling performance. We found that its enhanced electrochemical properties could be attributed to the homogeneous distribution of Pd nanoparticles on the Co3O4 nanowires, which ensured uniform growth of Li2O2 on the Pd/Co3O4/NF electrodes. This, in turn, significantly improved the cathode's OER/ORR activity and aided the formation of discharge products with uniform morphologies, as well as the decomposition of these discharge products during recharging.

A high performance doped carbon catalyst with ordered mesoporous structures and a high surface area (1217 m2 g−1) was prepared through a nanocasting-pyrolysis procedure by using poly(4-vinylpyridine) and iron chloride as the precursors and SBA-15 as the template. The catalyst exhibited excellent oxygen reduction reaction (ORR) performance, and was far more active than a commercial Pt/C catalyst in alkaline media, with its half-wave potential (−0.083 V, vs. Ag/AgCl) 64 mV more positive and current density at −0.1 V (vs. Ag/AgCl, −3.651 mA cm−2) almost three times higher than those of a commercial Pt/C catalyst (−0.147 V, vs. Ag/AgCl, and −0.967 mA cm−2), respectively. To our knowledge, it is one of the best carbon-based ORR catalysts to date in an alkaline medium. In addition to the outstanding ORR performance, our catalyst also illustrated excellent stability, methanol tolerance, and high catalytic efficiency. It is found that the total N contents and the compositions of each N species in the catalysts strongly depend on the pyrolysis temperatures. Furthermore, we found that the SBA-15 templates not only give catalysts well-defined mesoporous structures, but also seem to help increase the total N content whilst the proportion of each N species in the catalysts is not changed obviously.

Developing a high-performance Li–O2 battery demands an air electrode with a high-efficiency bifunctional catalyst. Here we designed a new type of bifunctional cathode catalyst by mounting ruthenium nanoparticles on reduced graphene oxide co-doped with nitrogen, iron, and cobalt. The catalyst exhibited significantly higher ORR and OER activities than a commercial Pt/C catalyst in both aqueous and non-aqueous electrolytes. With this novel catalyst as the cathode, the battery exhibited an ultra-high reversible capacity of 23905 mA h g−1 at a current density of 200 mA g−1. Furthermore, the battery also exhibited an excellent cycling stability—after 300 cycles of limited capacity, the discharge plateau potential decreased only slightly, and the energy efficiency was still above 60%. The battery also demonstrated good rate performance; with discharge current densities of up to 1000 and 2000 mA g−1, the capacities still reached 14560 and 6420 mA h g−1, respectively. We suggest that the excellent performance of our catalyst can be ascribed to the excellent ORR performance of the multielement co-doped graphene and the excellent OER performance of the mounted Ru nanoparticles. In addition, the nanosheet structure with high surface area of the multielement co-doped graphene may result in the formation of uniform Li2O2 nanocrystals, which make the formation (discharge) and decomposition (charge) processes much more reversible.

A novel hierarchical nano/microstructure of LiFePO4 microspheres consisting of nanofibers has been synthesized by a solvothermal approach with a mixture of water and 1,2-propanediol as solvent. The influences of temperature and solvent composition on the morphology and electrochemical performance of the products are investigated. The optimum temperature is 140 °C, and the optimum solvent composition is 1:5 for the volume ratio of water to 1,2-propanediol. The initial discharge capacity of the LiFePO4/C microsphere electrode is high and up to 163.9 mA h g−1 and the capacity increased gradually to 164.9 mA h g−1 after 10 cycles, indicating the excellent stability of the materials.

A core–shell structured catalyst, Pd1Ru1Ni2@Pt/C, with a ternary alloy as its core and a Pt monolayer shell was prepared using a two-stage strategy, in which Pd1Ru1Ni2 alloy nanoparticles were prepared by a chemical reduction method, and then the Pt monolayer shell was generated via an underpotential deposition method. It was found that the addition of Ni to the core played an important role in enhancing the catalyst's oxygen reduction activity and stability. The optimal molar ratio of Pd:Ru:Ni was about 1:1:2; the catalyst with this optimal ratio had a half-wave potential approximately 65 mV higher than that of a PdRu@Pt/C catalyst, and its mass activity was up to 1.06 A mg−1 Pt, which was more than five times that of a commercial Pt/C catalyst. The catalyst's structure and composition were characterized using X-ray powder diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and energy-dispersive X-ray spectrometry. The core–shell structure of the catalyst was demonstrated by the EDS mapping results and supported by the XPS results. We also performed a stability test that confirmed the catalyst's superior stability in comparison to that of commercial JM Pt/C (20 wt% Pt).

With a novel two-step approach, we prepared a low-cost, high-performance, binary transition metal nitride (BTMN) catalyst. An ammonia (NH3) complex of Ti and a transition metal was prepared in an organic solvent by the reaction of metal ions with ammonium; the complex then was dried in a vacuum oven, followed by nitridation in a tubular furnace under NH3 flow. The catalyst exhibited excellent activity towards the oxygen reduction reaction (ORR) in an alkaline medium and good ORR activity in an acidic medium. The effects of the doping elements (Fe, Co, and Ni), the doping concentration, and various nitriding temperatures on catalytic performance were intensively investigated. The onset potential of the Ti0.95Ni0.5N catalyst reached 0.83 V, with a limiting diffusion current density of 4 mA cm−2 (at a rotation speed of 1600 rpm) in 0.1 M HClO4 solution, which is the highest to date among the reported TiN-based electrocatalysts in an acidic medium. In 0.1 M KOH solution, the performance of this catalyst was almost comparable to that of commercial JM Pt/C; the diffusion current density reached 5.3 mA cm−2, and the halfway potential was only 71 mV inferior to that of commercial JM Pt/C. Furthermore, the catalyst showed high stability and only a slight drop in its current density after the durability test. All of these findings make our BTMN catalyst attractive for PEMFCs.

A hollow spherical doped carbon catalyst with a large surface area and hierarchical porous structure is prepared by pyrolyzing zeolitic imidazolate framework nanocrystals (Z8Ncs) impregnated/covered with iron phthalocyanines (FePcs). It is found that the doping of FePcs into the Z8Nc precursor plays a crucial role in the structural evolution of the resulting hollow-core porous carbon as well as its high catalytic performance. Doped carbon catalysts derived from either Z8Ncs or FePcs exhibit poor activity towards oxygen reduction, whereas the catalyst derived from Z8Ncs impregnated/covered with FePcs exhibits extremely high performance in both acidic and alkaline media. In 0.1 M HClO4, its onset potential reaches up to 0.910 V, and its half-potential (0.790 V) is only 60 mV lower than that of the 20 wt% Pt/C catalyst (0.850 V). In 0.1 M KOH, its ORR activity even surpasses that of Pt/C. We suggest that the high performance of the catalyst is attributable to the following factors: (i) the high active site density caused by doping FePcs into/onto the highly porous, N-rich Z8Ncs, (ii) the high surface area and adequate active site exposure caused by its hollow spherical morphology, and (iii) the hierarchical porous structure which further facilitates the diffusion and adsorption of oxygen molecules.

A high-performance doped carbon catalyst with ultrahigh surface area (1123 m2 g−1) and hierarchical porous structures was prepared through an economical, non-template pyrolyzing approach using cross-linked polystyrene, melamine and iron chloride as precursors. The catalyst exhibits excellent oxygen reduction reaction (ORR) performance, outstanding methanol tolerance, remarkable stability, and high catalytic efficiency (nearly 100% selectivity for the four-electron ORR process). Remarkably, its ORR activity can even surpass that of the commercial Pt/C catalyst in alkaline media, with a half-wave potential 20 mV more positive. To the best of our knowledge, it is also one of the most active ORR catalysts in alkaline media to date. By investigating the effects of N dopants and Fe residue on the catalyst's ORR performance, we find that residual Fe is as important as doped nitrogen in enhancing the ORR performance. The catalyst's high ORR performance, outstanding stability and excellent methanol tolerance, combined with its hierarchical porous morphology, make it promising for the application in novel, environmentally friendly electrochemical energy systems. This research also provides a potential way to turn waste into wealth.

In this paper, we report a one-step solution-phase approach to synthesize hexagonal close-packed (hcp) phase Co thin film composed of Co nanosheets generated by chemical reduction of Co2+–EDTA complexes under an external magnetic field. The as-prepared Co film was characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and superconducting quantum interference device (SQUID) magnetometer. The effects of synthetic conditions, such as solvents, reaction temperature and intensity of the magnetic field, on the morphology of the final products were investigated. The coercivity of the as-prepared Co thin film measured in the directions parallel and perpendicular to the film plane reached 321.7 Oe and 220.5 Oe, respectively, which was much higher than that of the bulk Co counterpart. The facile magnetic-field-assisted solution-phase route presented here may provide a new method to prepare magnetic thin film composed of magnetic nanocrystals with anisotropic shapes.