Exploring nonprecious metal electrocatalysts to replace the noble metal-based catalysts for full water electrocatalysis is still an ongoing challenge. In this work, porous structured ternary nickel–iron–phosphide (Ni–Fe–P) nanocubes were synthesized through one-step phosphidation of a Ni–Fe-based Prussian blue analogue. The Ni–Fe–P nanocubes exhibit a rough and loose porous structure on their surface under suitable phosphating temperature, which is favorable for the mass transfer and oxygen diffusion during the electrocatalysis process. As a result, Ni–Fe–P obtained at 350 °C with poorer crystallinity offers more unsaturated atoms as active sites to expedite the absorption of reactants. Additionally, the introduction of nickel improved the electronic structure and then reduced the charge-transfer resistance, which would result in a faster electron transport and an enhancement of the intrinsic electrocatalytic activities. Benefiting from the unique porous nanocubes and the chemical composition, the Ni–Fe–P nanocubes exhibit excellent hydrogen evolution reaction and oxygen evolution reaction activities in alkaline medium, with low overpotentials of 182 and 271 mV for delivering a current density of 10 mA cm–2, respectively. Moreover, the Ni–Fe–P nanocubes show outstanding stability for sustained water splitting in the two-electrode alkaline electrolyzer. This work not only provides a facile approach for designing bifunctional electrocatalysts but also further extends the application of metal–organic frameworks in overall water splitting.Keywords: metal−organic frameworks; overall water splitting; porous structure; Prussian blue analogue; ternary Ni−Fe−P nanocube;

Inspired by the excellent absorption capability of spongelike bacterial cellulose (BC), three-dimensional hierarchical porous carbon fibers doped with an ultrahigh content of N (21.2 atom %) (i.e., nitrogen-doped carbon fibers, NDCFs) were synthesized by an adsorption–swelling strategy using BC as the carbonaceous material. When used as anode materials for sodium-ion batteries, the NDCFs deliver a high reversible capacity of 86.2 mAh g–1 even after 2000 cycles at a high current density of 10.0 A g–1. It is proposed that the excellent Na+ storage performance is mainly due to the defective surface of the NDCFs created by the high content of N dopant. Density functional theory (DFT) calculations show that the defect sites created by N doping can strongly “host” Na+ and therefore contribute to the enhanced storage capacity.Keywords: bacterial cellulose; carbonization; highly N-doped; sodium storage; three-dimensional;

A facile and scalable solvothermal high-temperature treatment strategy was developed to construct few-layered ultrasmall MoS2 with less than three layers. These are embedded in carbon spheres (MoS2–C) and can be used as advanced anode material for lithium ion batteries (LIBs). In the resulting architecture, the intimate contact between MoS2 surface and carbon spheres can effectively avert aggregation and volume expansion of MoS2 during the lithiation–delithiation process. Moreover, it improves the structural integrity of the electrode remarkably, while the conductive carbon spheres provide quick transport of both electrons and ions within the electrode. Benefiting from this unique structure, the resulting hybrid manifests outstanding electrochemical performance, including an excellent rate capability (1085, 885, and 510 mAh g–1 at 0.5, 2, and 5 A g–1), and a superior cycling stability at high rates (maintaining 100% of the initial capacity following 500 cycles at 0.5 A g–1). Using identical methods, molybdenum carbide and phosphide supported on carbon spheres (Mo2C–C, and MoP–C) were prepared for LIBs. As a result, MoS2–C exhibits outstanding lithium storage capacities due to its specific layered structure. This study investigates large-scale production capabilities of few-layered structure ultrasmall MoS2 for energy storage, and thoroughly compares lithium storage performance of molybdenum compounds.Keywords: anode materials; carbon sphere; few-layered ultrasmall structure; lithium ion battery; various molybdenum compounds;

Controlling of the particle size and surface strain is the key to tuning the surface chemistry and optimizing the catalytic performance of electrocatalysts. Here, we show that by introducing both Fe and Co into Pd lattices, the surface strain of Pd nanocatalysts can be tuned to optimize their oxygen reduction activity in both fuel cells and Zn–air batteries. The Pd2FeCo/C alloy particles are uniquely coated with an ultrathin Fe2O3 shell which is in situ formed during a thermal annealing treatment. The thin shell acts as an effective barrier that prevents the coalescence and ripening of Pd2FeCo/C nanoparticles. Compared with Pd/C, Pd2FeCo/C exhibits higher catalytic activity and long-term stability for the ORR, signifying changes in catalytic behavior due to particle sizes and strain effects. Moreover, by spontaneous decoration of Pt on the surface of Pd2FeCo/C, the Pd2FeCo@Pt/C core@shell structure was formed and the Pt mass activity was about 37.6 and 112.5 times higher than that on Pt/C in a 0.1 M HClO4 and KOH solution at 0.9 V, respectively, suggesting an enhanced ORR performance after Pt decoration. More interestingly, Pd2FeCo@Pt/C also shows a power density of ∼308 mW cm−2, which is much higher than that of Pt/C (175 mW cm−2), and excellent durability in a home-made Zn–air battery.

Glucose-derived carbon sphere supported cobalt phosphide nanoparticles (CoP/C) were synthesized via a concise two-step method. The electrochemical measurement results indicate that the CoP/C prepared at 900 °C presents excellent electrocatalytic performance for hydrogen evolution reaction (HER). The overpotential at a current density of 10 mA cm−2 is 108 and 163 mV in 0.5 M H2SO4 and 1 M KOH, respectively, and maintains its electrocatalytic durability for at least 10 h. This work supplies a new field to challenge the construction of electrocatalysts for HER through using cost-effective carbon supported transition metal phosphides.Carbon sphere supported cobalt phosphide nanoparticles (CoP/C) were successfully synthesized through a facile two-step method. The CoP/C exhibits an efficient HER electrocatalytic activity and long-term durability in both acid and alkaline media. Carbon sphere acts as a substrate which can not only avoid the nanoparticles aggregation, but also facilitate the electron transfer during the electrocatalytic process.Download high-res image (247KB)Download full-size image

Electrochemical splitting of water to obtain hydrogen plays a vital role in high energy density devices, especially for fuel cells. In this work, reduced graphene oxide supported molybdenum phosphide nanoparticles (MoP-RGO) were prepared via a facile solvothermal reaction followed by high-temperature phosphating treatment. The electrochemical measurement results indicate that the MoP-RGO nanocomposite obtained at 900 °C exhibits excellent electrocatalytic activity for hydrogen evolution reaction (HER) with overpotentials of 117 mV and 150 mV at a current density of 10 mA cm−2 in acid and alkaline media, respectively. Furthermore, the instability of the catalyst in basic medium was systemically investigated. This work provides a facile strategy for the synthesis of cost-effective carbon supported metal phosphide as HER electrocatalyst.Graphene supported MoP (MoP-RGO) was synthesized through a facile solvothermal reaction followed by high-temperature phosphating treatment method. The material exhibits an outstanding HER performance in both acid and alkaline media. RGO act as a substrate which can not only avoid the nanoparticles aggregation, but also facilitate the electron transfer during the electrocatalytic process.Download high-res image (175KB)Download full-size image

The SiOC ceramic was prepared with vinyltriethoxysilane as the sol − gel precursor, and followed by etching with KOH. The effect of KOH etching on the morphology, structure and electrochemical properties of SiOC anodes was investigated. The amorphous SiOC ceramics with different free carbon content is obtained by KOH etching. The reaction of oxygen-enriched units with KOH and the activation of free carbon resulted in the formation of micro and mesopores. The galvanostatic charging/discharging and rate capability suggest that the electrochemical performance of SiOC ceramics is improved by KOH etching. As compared with SiOC sample, KOH-SiOC-5 (KOH/SiOC weight ratio of 5:1) with a high BET surface area of 249.2 m2 g−1 deliveres a discharge capacity of 607 mAh g−1 at the current density of 36 mA g−1. Nano-sized pores, mixed SiOxC4-x structures and the free carbon phase both work together for the excellent electrochemical performance. The contribution of carbon to reversible capacity is higher than that of SiOxC4-x phases and surface area. However, the specific surface area, pore volume and free carbon content are decreased by excessive etching with KOH, which resulted in the decrease of electrochemical properties.

Developing porous carbon materials with low-cost, sustainable and eco-friendly natural resources is emerging as an ever important research field in the application of high-performance supercapacitor. In this paper, a simple synthetic method to fabricate nitrogen doped porous carbon (NPC) is developed via a one-pot carbonization of sodium alginate and urea. The as-prepared NPC annealed at 700 °C with meso- and macro-porous structure exhibits excellent specific capacitance (180.2 F/g at 1 A/g) and superior cycling life when serves as electrode materials for supercapacitor. Moreover, the investigation on the annealing temperature demonstrates that NPC pyrolysis at 700 °C possesses relatively high pyrrole nitrogen and pyridine nitrogen, which is favorable for enhancing supercapacitor performance. This work extends biomass derived carbon materials in energy storage applications.Download high-res image (317KB)Download full-size imageNitrogen doped porous carbon derived from sodium alginate via one-pot pyrolysis method with meso- and macro-porous structure and appropriate nitrogen content exhibits superior supercapacitor performance with high specific capacitance and outstanding cycling stability.

A simple one-pot synthetic strategy for the general preparation of nitrogen doped carbon supported metal/metal oxides (Co@CoO/NDC, Ni@NiO/NDC and MnO/NDC) derived from the complexing function of (ethylenediamine)tetraacetic acid (EDTA) is developed. EDTA serves not only as a resource to tune the morphology in terms of the complexation constant for M–EDTA, but also as a nitrogen and oxygen source for nitrogen doping and metal oxide formation, respectively. When the materials are used as electrocatalysts for the oxygen electrode reaction, Co@CoO/NDC-700 and MnO/NDC-700 show superior electrocatalytic activity towards the oxygen reduction reaction (ORR), while Co@CoO/NDC-700 and Ni@NiO/NDC-700 exhibit excellent oxygen evolution reaction (OER) activities. Taken together, the resultant Co@CoO/NDC-700 exhibits the best catalytic activity with favorable reaction kinetics and durability as a bi-functional catalyst for the ORR and OER, which is much better than the other two catalysts, Pt/C and Ir/C. Moreover, as an air electrode for a homemade zinc–air battery, Co@CoO/NDC-700 shows superior cell performance with a highest power density of 192.1 mW cm−2, the lowest charge–discharge overpotential and high charge–discharge durability over 100 h.

Effective electrocatalysts for the hydrogen evolution reaction (HER) in alkaline electrolytes can be developed via a simple solvothermal process. In this work, first, the prepared CoMoS nanomaterials through solvothermal treatment have a porous, defect-rich, and vertically aligned nanostructure, which is beneficial for the HER in an alkaline medium. Second, electron transfer from cobalt to MoS2 that reduces the unoccupied d orbitals of molybdenum can also enhance the HER kinetics in an alkaline medium. This has been demonstrated via a comparison of the catalytic performances of CoMoS, CoS, and MoS2. Third, the solvothermal treatment time evidently impacts the electrocatalytic activity. As a result, after 24 h of solvothermal treatment, the prepared CoMoS nanomaterials exhibit the lowest onset potential (42 mV) and overpotential (98 mV) for delivering a current density of 10 mA cm–2 in a 1 M KOH solution. Thus, this study provides a simple method to prepare efficient electrocatalysts for the HER in an alkaline medium.Keywords: defect-rich nanosheets; electrocatalysts; hierarchically porous; hydrogen evolution reaction; vertically aligned;

3D-transition binary metal oxides have been considered as promising anode materials for lithium-ion batteries with improved reversible capacity, structural stability and electronic conductivity compared with single metal oxides. Here, carbon nanotube supported NiCo2O4 nanoparticles (NiCo2O4/CNT) with 3D hierarchical hollow structure are fabricated via a simple one-pot method. The NiCo2O4 nanoparticles with interconnected pores are consists of small nanocrystals. When used as anode material for the lithium-ion battery, NiCo2O4/CNT exhibits enhanced electrochemical performance than that of Co3O4/CNT and NiO/CNT. Moreover, ultra-high discharge/charge stability was obtained for 4000 cycles at a current density of 5 A g−1. The superior battery performance of NiCo2O4 nanoparticles is probably attributed to the special structural features and physical characteristics, including integrity, hollow structure with interconnected pores, which providing sufficient accommodation for the volume change during charge/discharge process. Besides, the consisting of ultra-small crystals enhanced the utility of active material, and intimate interaction with CNTs improved the electron-transfer rate.Carbon nanotube supported hollow structured NiCo2O4 nanoparticles with interconnected pores were fabricated via a simple one-pot method which possess excellent charge storage kinetics and exhibited ultra-high discharge/charge stability for 4000 cycles at a high-rate current density of 5 A g−1, when used as anode material for the lithium ion battery.Download high-res image (205KB)Download full-size image

Heteroatom doping, especially dual-doped carbon materials have attracted much attention for the past few years, and have been regarded as one of the most efficient strategies to enhance the capacitance behavior of porous carbon materials. In this work, a facile two-step synthetic route was developed to fabricate nitrogen and sulfur co-doped carbon microsphere (NSCM) by using thiourea as dopant. The N/S doping content is controlled via varying the carbonization temperature. It has been proved that a suitable quantity of N and S groups could not only provide pseudo-capacitance but also promote the electron transfer for carbon materials, which ensures the further utilization of the exposed surfaces for charge storage. The optimized NSCM prepared at a carbonization temperature of 800 °C (NSCM-800) achieves a capacitance of 277.1 F g−1 at a current density of 0.3 A g−1 in 6.0 mol L−1 KOH electrolyte, which is 71% higher than that of undoped carbon microsphere. Besides, NSCM-800 shows an excellent cycling stability, 98.2% of the initial capacitance is retained after 5,000 cycles at a current density of 3.0 A g−1.A high level of N/S co-doped carbon microsphere (NSCM) has been successfully prepared by using a modified post-processing procedure. The N/S doping content can be controlled via varying the carbonization temperature. The optimized NSCM delivers a high capacitance of 277.1 F g−1 at a current density of 0.3 A g−1, and shows an excellent cycling stability of 98.2% after 5000 cycles at high current density of 3.0 A g−1.Download high-res image (136KB)Download full-size image

In order to explore low-cost, high efficiency, precious metal-free materials for electrochemical water splitting, three types of molybdenum-based compounds (MoO2, MoC and Mo2C) were synthesized by tuning the ratio of glucose and ammonium molybdate via a two-step procedure. TEM images reveal a uniform dispersion of the three molybdenum-based nanoparticles on the carbon support, and in particular, MoC and Mo2C exhibit ultra-small particle sizes which are lower than 3 nm. When used as catalysts for the HER in both acid and basic media, Mo2C exhibits the best catalytic activity with a small overpotential of 135 mV in acid media and 96 mV in alkaline media at a current density of 10 mA cm−2, which is about 105 mV and 30 mV higher than that with Pt/C, respectively. The enhanced catalytic activity of Mo2C could originate from the excellent crystal structure, the high electronic conductivity of the carbon support with a high degree of graphitization and the ultra-small particle size, which provides a large surface area and active sites.

Exploring highly active, stable and relatively low-cost nanomaterials for the oxygen reduction reaction (ORR) is of vital importance for the commercialization of proton exchange membrane fuel cells (PEMFCs). Herein, a highly active, durable, carbon supported, and monolayer Pt coated Pd–Co–Zn nanoparticle is synthesized via a simple impregnation–reduction method, followed by spontaneous displacement of Pt. By tuning the atomic ratios, we obtain the composition–activity volcano curve for the Pd–Co–Zn nanoparticles and determined that Pd:Co:Zn = 8:1:1 is the optimal composition. Compared with pure Pd/C, the Pd8CoZn/C nanoparticles show a substantial enhancement in both the catalytic activity and the durability toward the ORR. Moreover, the durability and activity are further enhanced by forming a Pt skin on Pd8CoZn/C nanocatalysts. Interestingly, after 10000 potential cycles in N2-saturated 0.1 M HClO4 solution, Pd8CoZn@Pt/C shows improved mass activity (2.62 A mg−1Pt) and specific activity (4.76 A m−2total), which are about 1.4 and 4.4 times higher than the initial values, and 37.4 and 5.5 times higher than those of Pt/C catalysts, respectively. After accelerated stability testing in O2-saturated 0.1 M HClO4 solution for 30000 potential cycles, the half-wave potential negatively shifts about 6 mV. The results show that the Pt skin plays an important role in enhancing the activity as well as preventing degradation.

Investigating active, stable, and low-cost materials for the oxygen reduction reaction is one of the key challenges in fuel-cell research. In this work, we describe the formation of N-doped carbon shell coated Co@CoO nanoparticles supported on Vulcan XC-72 carbon materials (Co@CoO@N–C/C) based on a simple supramolecular gel-assisted method. The double-shelled Co@CoO@N–C/C core–shell nanoparticles exhibit superior electrocatalytic activities for the oxygen reduction reaction compared to N-doped carbon and cobalt oxides, demonstrating the synergistic effect of the hybrid nanomaterials. Notably, the Co@CoO@N–C/C nanoparticles give rise to a comparable four-electron selectivity, long-term stability, and high methanol tolerance; all show a multi-fold improvement over the commercial Pt/C catalyst. The progress is of great importance in exploring advanced non-precious metal-based electrocatalysts for fuel cell applications.

Preventing the stacking of graphene sheets is of vital importance for highly efficient and stable fuel cell electrocatalysts. In the present work, we report a 3-D structured carbon nanotube intercalated graphene nanoribbon with N/S co-doping. The nanocomposite is obtained by using high temperature heat-treated thiourea with partially unzipped multi-walled carbon nanotubes. The unique structure preserves both the properties of carbon nanotubes and graphene, exhibiting excellent catalytic performance for the ORR with similar onset and half-wave potentials to those of Pt/C electrocatalysts. Moreover, the stereo structured composite exhibits distinct advantages in long-term stability and methanol poisoning tolerance in comparison to Pt/C.

In the present work, we report nitrogen and phosphorus co-doped 3-D structured carbon nanotube intercalated graphene nanoribbon composite. The graphene nanoribbons are prepared via partial exfoliation of multi-walled carbon nanotubes. In the graphene nanoribbons/CNTs composite, carbon nanotubes play a role of skeleton and support the exfoliated graphene nanoribbons to form the stereo structure. After high temperature heat-treatment with ammonium dihydrogen phosphate, the unique structure reserves both the properties of carbon nanotube and graphene, exhibiting excellent catalytic performance for the ORR with excellent onset and half-wave potential, which is similar to commercial Pt/C electrocatalysts.Nitrogen and phosphorus co-doped graphene nanoribbons/CNTs composite with 3-D stereo structure obtained by oxidation and exfoliation of multi-walled carbon nanotubes and following high temperature heat-treatment work as efficient electro-catalyst for the oxygen reduction reaction.

Improving the catalytic activity of Pt-based bimetallic nanoparticles is a key challenge in the application of proton-exchange membrane fuel cells. Electrochemical dealloying represents a powerful approach for tuning the surface structure and morphology of these catalyst nanoparticles. We present a comprehensive study of using electrochemical dealloying methods to control the morphology of ordered Cu3Pt/C intermetallic nanoparticles, which could dramatically affect their electrocatalytic activity for the oxygen reduction reaction (ORR). Depending on the electrochemical dealloying conditions, the nanoparticles with Pt-rich core–shell or porous structures were formed. We further demonstrate that the core–shell and porous morphologies can be combined to achieve the highest ORR activity. This strategy provides new guidelines for optimizing nanoparticles synthesis and improving electrocatalytic activity.

A carbon black incorporated nitrogen and sulfur co-doped graphene (NSGCB) nanocomposite has been synthesized through one-pot annealing of a precursor mixture containing graphene oxide, thiourea, and acidized carbon black (CB). The NSGCB shows excellent performance for the oxygen reduction reaction (ORR) with the onset and half-wave potentials at 0.96 V and 0.81 V (vs. RHE), respectively, which are significantly higher compared to those of the catalysts derived from only graphene (0.90 V and 0.76 V) or carbon nanospheres (0.82 V and 0.74 V). The enhanced catalytic activity of the NSGCB electrode could be attributed to the synergistic effect of N/S co-doping and the enlarged interlayer space resulted from the insertion of carbon nanospheres into the graphene sheets. The four-electron selectivity and the limiting current density of the NSGCB nanocomposite are comparable to those of the commercial Pt/C catalyst. Furthermore, the NSGCB nanocomposite is superior to Pt/C in terms of long-term durability and tolerance to methanol poisoning.

Controlling the size, composition, and structure of bimetallic nanoparticles is of particular interest in the field of electrocatalysts for fuel cells. In the present work, structurally ordered nanoparticles with intermetallic phases of Pt3Zn and PtZn have been successfully synthesized via an impregnation reduction method, followed by post heat-treatment. The Pt3Zn and PtZn ordered intermetallic nanoparticles are well dispersed on a carbon support with ultrasmall mean particle sizes of ∼5 nm and ∼3 nm in diameter, respectively, which are credited to the evaporation of the zinc element at high temperature. Meanwhile, these catalysts are less susceptible to CO poisoning relative to Pt/C and exhibited enhanced catalytic activity and stability toward formic acid electrooxidation. The mass activities of the as-prepared catalysts were approximately 2 to 3 times that of commercial Pt at 0.5 V (vs. RHE). This facile synthetic strategy is scalable for mass production of catalytic materials.

Carbon supported Pd3V bimetallic alloy nanoparticles (Pd3V/C) have been successfully synthesized via a simple impregnation–reduction method, followed by high temperature treatment under a H2 atmosphere. Electrochemical tests reveal that the half-wave potential of Pd3V/C-500 shifts positively 40 mV compared with Pd/C. However, the catalytic activity of Pd3V/C-500 suffers from serious degradation after 1k cycles. By a spontaneous displacement reaction or co-reduction method, a trace amount of Pt was decorated on the surface or inside of the Pd3V/C nanoparticles. The catalytic activity and stability of the Pd3V@Pt/C and Pt-Pd3V/C catalysts for the oxygen reduction reaction (ORR) are enhanced significantly, and are comparable to commercial Pt/C. In addition, the Pt mass activity of Pd3V@Pt/C and Pt-Pd3V/C improves by factors of 10.9 and 6.5 at 0.80 V relative to Pt/C. Moreover, Pt-decorated Pd3V/C nanoparticles show almost no obvious morphology change after durability tests, because the Pt-rich shell plays an important role in preventing degradation.

A template- and surfactant-free strategy is developed to prepare a hollow structured Co2FeO4/MWCNT electrocatalyst, which has been successfully used as a highly efficient non-precious metal electrocatalyst for the oxygen reduction reaction (ORR) in alkaline media. The hollow structured Co2FeO4 particles are transformed from solid Co2Fe nanoparticles via the Kirkendall effect, which increases their active sites and improves the contact between the electrolyte and catalyst surfaces and then enhances the electrocatalytic activity. Furthermore, the hollow structured Co2FeO4/MWCNT exhibits excellent long term stability and high methanol tolerance compared to commercial Pt/C. The hollow structured Co2FeO4/MWCNT electrocatalysts synthesized herein are promising electrode materials for fuel cell applications and the facile synthesis method could be used in low-cost and large-scale materials production, facilitating the screening of high efficiency catalysts.

We have developed a template-free procedure to synthesize Co3O4 hollow-structured nanoparticles on a Vulcan XC-72 carbon support. The material was synthesized via an impregnation–reduction method followed by air oxidation. In contrast to spherical particles, the hollow-structured Co3O4 nanoparticles exhibited excellent lithium storage capacity, rate capability, and cycling stability when used as the anode material in lithium-ion batteries. Electrochemical testing showed that the hollow-structured Co3O4 particles delivered a stable reversible capacity of about 880 mAh/g (near the theoretical capacity of 890 mAh/g) at a current density of 50 mA/g after 50 cycles. The superior electrochemical performance is attributed to its unique hollow structure, which combines nano- and microscale properties that facilitate electron transfer and enhance structural robustness.Keywords: anode materials; cobalt oxides; electrochemistry; hollowed structure; lithium battery;

•A facile way is developed to synthesize various molybdenum compounds.•Electrocatalytic performance of the catalysts is investigated detailed in both acid and alkaline media.•The prepared catalysts possess different structures, including few layered and nanoparticle morphologies.•Carbon sphere plays an important role on improving the catalytic activity.Efficient electrocatalysts for hydrogen evolution reaction (HER) were developed based on the homogeneous dispersion of molybdenum composites (MoP, Mo2C, MoS2) on a glucose- derived carbon sphere matrix obtained by simply changing the precursors during the high temperature treatment. The potential composite materials showed different performance characteristics in different experimental designs. The as-synthesized MoP showed the best HER performance in acid medium with a low overpotential of 136 mV obtained at 10 mA cm−2, while Mo2C-C showed the lowest overpotential for HER in alkaline medium, and for MoS2-C, which exhibited few layers structure (less than three layers), exhibiting favorable catalytic performance in both acid and alkaline electrolytes. Both MoP-C and Mo2C-C showed negligible overpotential loss after 5000 cycles in acid medium, but were relative unstable in alkaline medium. Moreover, the carbon sphere matrix improved the catalytic performance of molybdenum compounds by alleviating the aggregation of catalysts, providing sufficient area for electrolyte contact, and facilitating electron transfer. This work demonstrates a facile avenue to prepare cost-effective molybdenum compounds for HER. Furthermore, electrochemical performance of the catalysts was investigated in both acid and basic media.A novel and facile synthetic route was developed for the controllable preparation of molybdenum compounds (MoP, Mo2C and MoS2) supported on carbon spheres by post high temperature treatment of the solvothermal products. The catalytic activities for hydrogen evolution reaction (HER) of Molybdenum compounds were investigated in both acid and basic media systemically.

Controlling of the particle size and surface strain is the key to tuning the surface chemistry and optimizing the catalytic performance of electrocatalysts. Here, we show that by introducing both Fe and Co into Pd lattices, the surface strain of Pd nanocatalysts can be tuned to optimize their oxygen reduction activity in both fuel cells and Zn–air batteries. The Pd2FeCo/C alloy particles are uniquely coated with an ultrathin Fe2O3 shell which is in situ formed during a thermal annealing treatment. The thin shell acts as an effective barrier that prevents the coalescence and ripening of Pd2FeCo/C nanoparticles. Compared with Pd/C, Pd2FeCo/C exhibits higher catalytic activity and long-term stability for the ORR, signifying changes in catalytic behavior due to particle sizes and strain effects. Moreover, by spontaneous decoration of Pt on the surface of Pd2FeCo/C, the Pd2FeCo@Pt/C core@shell structure was formed and the Pt mass activity was about 37.6 and 112.5 times higher than that on Pt/C in a 0.1 M HClO4 and KOH solution at 0.9 V, respectively, suggesting an enhanced ORR performance after Pt decoration. More interestingly, Pd2FeCo@Pt/C also shows a power density of ∼308 mW cm−2, which is much higher than that of Pt/C (175 mW cm−2), and excellent durability in a home-made Zn–air battery.

Preventing the stacking of graphene sheets is of vital importance for highly efficient and stable fuel cell electrocatalysts. In the present work, we report a 3-D structured carbon nanotube intercalated graphene nanoribbon with N/S co-doping. The nanocomposite is obtained by using high temperature heat-treated thiourea with partially unzipped multi-walled carbon nanotubes. The unique structure preserves both the properties of carbon nanotubes and graphene, exhibiting excellent catalytic performance for the ORR with similar onset and half-wave potentials to those of Pt/C electrocatalysts. Moreover, the stereo structured composite exhibits distinct advantages in long-term stability and methanol poisoning tolerance in comparison to Pt/C.

In order to explore low-cost, high efficiency, precious metal-free materials for electrochemical water splitting, three types of molybdenum-based compounds (MoO2, MoC and Mo2C) were synthesized by tuning the ratio of glucose and ammonium molybdate via a two-step procedure. TEM images reveal a uniform dispersion of the three molybdenum-based nanoparticles on the carbon support, and in particular, MoC and Mo2C exhibit ultra-small particle sizes which are lower than 3 nm. When used as catalysts for the HER in both acid and basic media, Mo2C exhibits the best catalytic activity with a small overpotential of 135 mV in acid media and 96 mV in alkaline media at a current density of 10 mA cm−2, which is about 105 mV and 30 mV higher than that with Pt/C, respectively. The enhanced catalytic activity of Mo2C could originate from the excellent crystal structure, the high electronic conductivity of the carbon support with a high degree of graphitization and the ultra-small particle size, which provides a large surface area and active sites.

A template- and surfactant-free strategy is developed to prepare a hollow structured Co2FeO4/MWCNT electrocatalyst, which has been successfully used as a highly efficient non-precious metal electrocatalyst for the oxygen reduction reaction (ORR) in alkaline media. The hollow structured Co2FeO4 particles are transformed from solid Co2Fe nanoparticles via the Kirkendall effect, which increases their active sites and improves the contact between the electrolyte and catalyst surfaces and then enhances the electrocatalytic activity. Furthermore, the hollow structured Co2FeO4/MWCNT exhibits excellent long term stability and high methanol tolerance compared to commercial Pt/C. The hollow structured Co2FeO4/MWCNT electrocatalysts synthesized herein are promising electrode materials for fuel cell applications and the facile synthesis method could be used in low-cost and large-scale materials production, facilitating the screening of high efficiency catalysts.

Carbon supported Pd3V bimetallic alloy nanoparticles (Pd3V/C) have been successfully synthesized via a simple impregnation–reduction method, followed by high temperature treatment under a H2 atmosphere. Electrochemical tests reveal that the half-wave potential of Pd3V/C-500 shifts positively 40 mV compared with Pd/C. However, the catalytic activity of Pd3V/C-500 suffers from serious degradation after 1k cycles. By a spontaneous displacement reaction or co-reduction method, a trace amount of Pt was decorated on the surface or inside of the Pd3V/C nanoparticles. The catalytic activity and stability of the Pd3V@Pt/C and Pt-Pd3V/C catalysts for the oxygen reduction reaction (ORR) are enhanced significantly, and are comparable to commercial Pt/C. In addition, the Pt mass activity of Pd3V@Pt/C and Pt-Pd3V/C improves by factors of 10.9 and 6.5 at 0.80 V relative to Pt/C. Moreover, Pt-decorated Pd3V/C nanoparticles show almost no obvious morphology change after durability tests, because the Pt-rich shell plays an important role in preventing degradation.

Controlling the size, composition, and structure of bimetallic nanoparticles is of particular interest in the field of electrocatalysts for fuel cells. In the present work, structurally ordered nanoparticles with intermetallic phases of Pt3Zn and PtZn have been successfully synthesized via an impregnation reduction method, followed by post heat-treatment. The Pt3Zn and PtZn ordered intermetallic nanoparticles are well dispersed on a carbon support with ultrasmall mean particle sizes of ∼5 nm and ∼3 nm in diameter, respectively, which are credited to the evaporation of the zinc element at high temperature. Meanwhile, these catalysts are less susceptible to CO poisoning relative to Pt/C and exhibited enhanced catalytic activity and stability toward formic acid electrooxidation. The mass activities of the as-prepared catalysts were approximately 2 to 3 times that of commercial Pt at 0.5 V (vs. RHE). This facile synthetic strategy is scalable for mass production of catalytic materials.

A carbon black incorporated nitrogen and sulfur co-doped graphene (NSGCB) nanocomposite has been synthesized through one-pot annealing of a precursor mixture containing graphene oxide, thiourea, and acidized carbon black (CB). The NSGCB shows excellent performance for the oxygen reduction reaction (ORR) with the onset and half-wave potentials at 0.96 V and 0.81 V (vs. RHE), respectively, which are significantly higher compared to those of the catalysts derived from only graphene (0.90 V and 0.76 V) or carbon nanospheres (0.82 V and 0.74 V). The enhanced catalytic activity of the NSGCB electrode could be attributed to the synergistic effect of N/S co-doping and the enlarged interlayer space resulted from the insertion of carbon nanospheres into the graphene sheets. The four-electron selectivity and the limiting current density of the NSGCB nanocomposite are comparable to those of the commercial Pt/C catalyst. Furthermore, the NSGCB nanocomposite is superior to Pt/C in terms of long-term durability and tolerance to methanol poisoning.