A raisin bread-like electrocatalyst composed of iron sulfides (Fe1−xS) and nitrogen and sulfur dual-doped mesoporous graphitic carbon spheres (N, S-MGCSs) is successfully synthesized via a two-step pyrolysis and acid leaching process. The resulting Fe1−xS/N, S-MGCS catalysts demonstrate excellent electrocatalytic activities towards the oxygen reduction reaction (ORR) in alkaline and acidic media, the activities of which are closely related to the content and distribution of iron sulfide species. The most optimized electrocatalytic activity achieved over (Fe1−xS/N, S-MGCS)0.2 even outperforms that of the commercial Pt/C catalyst in alkaline media, and is close to that of highly active non-precious metal catalysts reported so far in acidic media. The remarkable catalytic performance is ascribed to the iron sulfide nanocrystals introduced into the highly conductive carbon supports for significantly enhancing the reactivity of catalytically active sites, and the raisin bread-like structure constructed for improving the characteristics of electron and ion transport and inhibiting the self-aggregation and leaching of iron sulfide species. Moreover, this work inspires a new consideration in the field for understanding the catalytic roles of the doped carbon species and transition metal chalcogenides during the ORR electrocatalysis.

A raisin bread-like electrocatalyst composed of iron sulfides (Fe1−xS) and nitrogen and sulfur dual-doped mesoporous graphitic carbon spheres (N, S-MGCSs) is successfully synthesized via a two-step pyrolysis and acid leaching process. The resulting Fe1−xS/N, S-MGCS catalysts demonstrate excellent electrocatalytic activities towards the oxygen reduction reaction (ORR) in alkaline and acidic media, the activities of which are closely related to the content and distribution of iron sulfide species. The most optimized electrocatalytic activity achieved over (Fe1−xS/N, S-MGCS)0.2 even outperforms that of the commercial Pt/C catalyst in alkaline media, and is close to that of highly active non-precious metal catalysts reported so far in acidic media. The remarkable catalytic performance is ascribed to the iron sulfide nanocrystals introduced into the highly conductive carbon supports for significantly enhancing the reactivity of catalytically active sites, and the raisin bread-like structure constructed for improving the characteristics of electron and ion transport and inhibiting the self-aggregation and leaching of iron sulfide species. Moreover, this work inspires a new consideration in the field for understanding the catalytic roles of the doped carbon species and transition metal chalcogenides during the ORR electrocatalysis.

Correction for ‘Cobalt ion-coordinated self-assembly synthesis of nitrogen-doped ordered mesoporous carbon nanosheets for efficiently catalyzing oxygen reduction’ by Haitao Wang, et al., Nanoscale, 2017, 9, 15534–15541.

Correction for ‘Cobalt ion-coordinated self-assembly synthesis of nitrogen-doped ordered mesoporous carbon nanosheets for efficiently catalyzing oxygen reduction’ by Haitao Wang, et al., Nanoscale, 2017, 9, 15534–15541.

Developing a facile strategy to synthesize an efficient and inexpensive catalyst for the oxygen reduction reaction (ORR) is critical to the commercialization of many sustainable energy storage and conversion techniques. Herein, a novel and convenient strategy was presented to prepare Fe3O4 embedded into nitrogen-doped mesoporous carbon spheres (Fe3O4/N-MCS) by the polycondensation between methylolmelamines and ammonium ferric citrate (AFC) and subsequent pyrolysis process. In particular, the polycondensation reaction was completely finished within a very short time (6.5 min), and the iron contents can be adjusted and had a great influence on the microstructure. Moreover, the Fe3O4/N-MCS can be used as a robust catalyst for the ORR in alkaline media, and the catalyst with the iron content of 3.35 wt % exhibited excellent electrochemical performance in terms of more positive onset potential (E0 = 1.036 V vs RHE) and half-wave potential (E1/2 = 0.861 V) and much better methanol tolerance and long-term durability, in comparison with that of 20% Pt/C. The remarkable performance was ascribed to the characteristics of large specific surface area, mesoporous structure, high contents of pyridinic N and graphitic N, as well as strong electronic interaction between Fe3O4 and protective N-doped graphitic layers.Keywords: ammonium ferric citrate; iron oxides; mesoporous structure; nitrogen-doped carbon matrices; oxygen reduction reaction;

The design and synthesis of a promising porous carbon-based electrocatalyst with an ordered and uninterrupted porous structure for oxygen reduction reaction (ORR) is still a significant challenge. Herein, an efficient catalyst based on cobalt-embedded nitrogen-doped ordered mesoporous carbon nanosheets (Co/N-OMCNS) is successfully prepared through a two-step procedure (cobalt ion-coordinated self-assembly and carbonization process) using 3-aminophenol as a nitrogen source, cobalt acetate as a cobalt source and Pluronic F127 as a mesoporous template. This work indicates that the formation of a two dimensional nanosheet structure is directly related to the extent of the cobalt ion coordination interaction. Moreover, the critical roles of pyrolysis temperature in nitrogen doping and ORR catalytic activity are also investigated. Benefiting from the high surface area and graphitic degree, high contents of graphitic N and pyridinic N, ordered interconnected mesoporous carbon framework, as well as synergetic interaction between the cobalt nanoparticles and protective nitrogen doped graphitic carbon layer, the resultant optimal catalyst Co/N-OMCNS-800 (pyrolyzed at 800 °C) exhibits comparable ORR catalytic activity to Pt/C, superior tolerance to methanol crossover and stability.

•A facile approach is proposed to synthesize ultra-small Fe2N nanocrystals/MNGCS.•The Fe2N content and BET surface area of Fe2N/MNGCS can be adjusted by altering the acid etching time.•The optimized Fe2N/MNGCS catalyst demonstrates better ORR performance than 10 wt% Pt/C catalyst.•Such excellent performance is ascribed to the rational balance of the density of Fe–N/C active sites, and the transport of electron and electrolyte ion.A low-cost, highly active, stable, and methanol tolerant electrocatalyst towards the oxygen reduction reaction (ORR) is extremely desirable for promoting the commercialization of fuel cells. Herein, we reported a facile two-step pyrolysis and acid leaching process to synthesize a high performance ORR electrocatalyst, where ultra-small Fe2N nanocrystals were incorporated into mesoporous nitrogen-doped graphitic carbon spheres (MNGCS). The Fe2N/MNGCS electrocatalysts with difference Fe2N contents and BET surface areas were obtained via altering the acid leaching time, and all exhibited the apparent electrocatalytic activity. The optimized ORR activity was achieved over (Fe2N/MNGCS)4 with the positive half-wave potentials (0.881 V vs RHE), high selectivity (4 e− process), excellent long-term stability (95.2% of the initial current remaining after 60,000 s of continuous operation) and good tolerance against methanol-crossover effect (94.9% of the current retained prior to 4.0 M methanol injection) in alkaline media, which even was more superior to that of commercial Pt/C catalyst. The remarkable ORR activity was originated from the cooperative effect of ultra-small Fe2N nanocrystals and MNGCS, where the balance of catalytic active site density, mesoporous structure, BET specific surface area, and electron conductivity played a key role in determining the ORR performance.

A facile approach is reported to synthesize (Fe,Co)@nitrogen-doped graphitic carbon (NGC) nanocubes (NCs) via the pyrolysis of polydopamine-encapsulated Fe3[Co(CN)6]2 NCs at 700 °C. Besides the comparable catalytic activity for oxygen reduction reaction (ORR) to the Pt/C catalyst, it showed much more outstanding catalytic selectivity and superior durability.

•MOx nanorod arrays are grown on the carbon fiber papers via a hydrothermal method.•GNR and GNS are deposited on the MOx nanorods via a facile dipping-coating method.•The electrochemical performance is enhanced with the introduction of GNR and GNS.•A high performance (MOx/GNR)@GNS-based solid-stated cells is successfully achieved.Electrochemical capacitors and rechargeable batteries are still limited in applications by the low energy and power densities they can deliver, respectively, holding back their deployment in electric vehicles. Here we develop a type of solid-state hybrid cells (SHCs) composed of graphene nanoribbons and nanosheets-coated metal oxide nanorod arrays ((MOx/GNR)@GNS). GNR and GNS are deposited on the surface of MOx nanorod arrays to improve the electron transport characteristic, and thus enhance the energy storage performance. The (MOx/GNR)@GNS-based SHCs can achieve a maximum volumetric energy density of 0.9 mWh cm−3, and still retain 0.4 mWh cm−3 even at 0.1 W cm−3. The energy storage performance is much better than the electrochemical capacitors reported previously, and can even rival the commercial Li thin-film battery but with a significantly higher power density, lower cost and higher safety. Also demonstrated is the good long-term cycle life with only ∼17% loss after 2500 cycles. These salient features make the (MOx/GNR)@GNS composites-based SHCs a strong contender for electrochemical energy storage.

We report on the development of highly conductive NiCo2S4 single crystalline nanotube arrays grown on a flexible carbon fiber paper (CFP), which can serve not only as a good pseudocapacitive material but also as a three-dimensional (3D) conductive scaffold for loading additional electroactive materials. The resulting pseudocapacitive electrode is found to be superior to that based on the sibling NiCo2O4 nanorod arrays, which are currently used in supercapacitor research due to the much higher electrical conductivity of NiCo2S4. A series of electroactive metal oxide materials, including CoxNi1–x(OH)2, MnO2, and FeOOH, were deposited on the NiCo2S4 nanotube arrays by facile electrodeposition and their pseudocapacitive properties were explored. Remarkably, the as-formed CoxNi1–x(OH)2/NiCo2S4 nanotube array electrodes showed the highest discharge areal capacitance (2.86 F cm–2 at 4 mA cm–2), good rate capability (still 2.41 F cm–2 at 20 mA cm–2), and excellent cycling stability (∼4% loss after the repetitive 2000 cycles at a charge–discharge current density of 10 mA cm–2).

The controllable synthesis of transition metal oxide nanomaterials has attracted considerable attention for the replacement of the current precious metal catalysts. Herein, we have developed a facile method to successfully synthesize Mn3O4–CoO core–shell mesoporous spheres, which are wrapped by carbon nanotubes (CNT), and investigated the catalytic activity for the oxygen reduction reaction (ORR) and CO oxidation for the first time. The ORR process on the Mn3O4–CoO/CNT catalysts was via a complete oxygen reduction process (4e−), and the catalytic activity was far better than for the Mn3O4/CNT and CoO/CNT catalysts. The durability even out-performed the commercial Pt/C catalysts. As compared with the Mn3O4/CNT and CoO/CNT catalysts, the Mn3O4–CoO/CNT catalysts also exhibited better catalytic activity for CO oxidation. The initial and complete conversion temperatures for the Mn3O4–CoO/CNT catalysts can decrease to 30 and 120 °C, respectively. The good catalytic activity for the ORR and CO oxidation is due to the high specific surface area (138.9 m2 g−1) provided which gives many catalytically active sites, mesoporous structure (15 to 120 nm) favoured for molecule accessibility to the active surface of the nanocrystals and mass transport, and the synergistic catalytic effect of Mn3O4 and CoO catalytically active sites.

The electrochemical performance of the pseudocapacitive materials is seriously limited by poor electron and ions transport. Herein, an advanced integrated electrode has been designed by growing the pseudocapacitive materials, including CoxNi1–x(OH)2, CoxNi1–xO, and (CoxNi1–x)9S8, on a three-dimensional hollow carbon nanorod arrays (HCNA) scaffold. The HCNA scaffold not only can provide large surface area for increasing the mass loading of the pseudocapacitive materials, but also is with good electrical conductivity and hollow structure for facilitating fast electron and electrolyte ions transport, and thus improve the electrochemical performance. Particularly, in comparison with CoxNi1–x(OH)2 and CoxNi1–xO nanosheets, (CoxNi1–x)9S8 nanosheets on the HCNA scaffold exhibit better electrochemical performance. The discharge areal capacitance of the (CoxNi1–x)9S8/HCNA electrode can be achieved to 1.32 F cm–2 at 1 mA cm–2, ∼1.5 times as that of the CoxNi1–x(OH)2/HCNA electrode. The rate capability performance is also improved. 71.8% of the capacitance is retained with increasing the discharge current density from 1 to 10 mA cm–2, in contrast to ∼59.9% for the CoxNi1–x(OH)2/HCNA electrode. Remarkably, the cycling stability is significantly enhanced. ∼111.2% of the initial capacitance is gained instead of decaying after the 3000 cycles at 8 mA cm–2, while there is ∼11.5% loss for the CoxNi1–x(OH)2/HCNA electrode tested under the same condition. Such good electrochemical performance can be ascribed by that (CoxNi1–x)9S8 exhibits the similar energy storage mechanism as CoxNi1–x(OH)2 and CoxNi1–xO, and more importantly, is with better electrical conductivity.Keywords: (Co, Ni)-based compounds; carbon fiber paper; hollow carbon nanorod array; supercapacitors; three-dimensional; ZnO nanorod array;

Self-standing single crystalline NiCo2S4 hollow nanorod arrays are prepared for catalysing the polysulfide redox couple in quantum dot-sensitized solar cells (QDSCs). The QDSCs using NiCo2S4 as a counter electrode (CE) achieved a power conversion efficiency of 4.22%, which exceeds the performance of QDSCs based on a Pt CE by 38.4%.

A raisin bread-like electrocatalyst composed of iron sulfides (Fe1−xS) and nitrogen and sulfur dual-doped mesoporous graphitic carbon spheres (N, S-MGCSs) is successfully synthesized via a two-step pyrolysis and acid leaching process. The resulting Fe1−xS/N, S-MGCS catalysts demonstrate excellent electrocatalytic activities towards the oxygen reduction reaction (ORR) in alkaline and acidic media, the activities of which are closely related to the content and distribution of iron sulfide species. The most optimized electrocatalytic activity achieved over (Fe1−xS/N, S-MGCS)0.2 even outperforms that of the commercial Pt/C catalyst in alkaline media, and is close to that of highly active non-precious metal catalysts reported so far in acidic media. The remarkable catalytic performance is ascribed to the iron sulfide nanocrystals introduced into the highly conductive carbon supports for significantly enhancing the reactivity of catalytically active sites, and the raisin bread-like structure constructed for improving the characteristics of electron and ion transport and inhibiting the self-aggregation and leaching of iron sulfide species. Moreover, this work inspires a new consideration in the field for understanding the catalytic roles of the doped carbon species and transition metal chalcogenides during the ORR electrocatalysis.

A raisin bread-like electrocatalyst composed of iron sulfides (Fe1−xS) and nitrogen and sulfur dual-doped mesoporous graphitic carbon spheres (N, S-MGCSs) is successfully synthesized via a two-step pyrolysis and acid leaching process. The resulting Fe1−xS/N, S-MGCS catalysts demonstrate excellent electrocatalytic activities towards the oxygen reduction reaction (ORR) in alkaline and acidic media, the activities of which are closely related to the content and distribution of iron sulfide species. The most optimized electrocatalytic activity achieved over (Fe1−xS/N, S-MGCS)0.2 even outperforms that of the commercial Pt/C catalyst in alkaline media, and is close to that of highly active non-precious metal catalysts reported so far in acidic media. The remarkable catalytic performance is ascribed to the iron sulfide nanocrystals introduced into the highly conductive carbon supports for significantly enhancing the reactivity of catalytically active sites, and the raisin bread-like structure constructed for improving the characteristics of electron and ion transport and inhibiting the self-aggregation and leaching of iron sulfide species. Moreover, this work inspires a new consideration in the field for understanding the catalytic roles of the doped carbon species and transition metal chalcogenides during the ORR electrocatalysis.

The controllable synthesis of transition metal oxide nanomaterials has attracted considerable attention for the replacement of the current precious metal catalysts. Herein, we have developed a facile method to successfully synthesize Mn3O4–CoO core–shell mesoporous spheres, which are wrapped by carbon nanotubes (CNT), and investigated the catalytic activity for the oxygen reduction reaction (ORR) and CO oxidation for the first time. The ORR process on the Mn3O4–CoO/CNT catalysts was via a complete oxygen reduction process (4e−), and the catalytic activity was far better than for the Mn3O4/CNT and CoO/CNT catalysts. The durability even out-performed the commercial Pt/C catalysts. As compared with the Mn3O4/CNT and CoO/CNT catalysts, the Mn3O4–CoO/CNT catalysts also exhibited better catalytic activity for CO oxidation. The initial and complete conversion temperatures for the Mn3O4–CoO/CNT catalysts can decrease to 30 and 120 °C, respectively. The good catalytic activity for the ORR and CO oxidation is due to the high specific surface area (138.9 m2 g−1) provided which gives many catalytically active sites, mesoporous structure (15 to 120 nm) favoured for molecule accessibility to the active surface of the nanocrystals and mass transport, and the synergistic catalytic effect of Mn3O4 and CoO catalytically active sites.

Self-standing single crystalline NiCo2S4 hollow nanorod arrays are prepared for catalysing the polysulfide redox couple in quantum dot-sensitized solar cells (QDSCs). The QDSCs using NiCo2S4 as a counter electrode (CE) achieved a power conversion efficiency of 4.22%, which exceeds the performance of QDSCs based on a Pt CE by 38.4%.

A facile approach is reported to synthesize (Fe,Co)@nitrogen-doped graphitic carbon (NGC) nanocubes (NCs) via the pyrolysis of polydopamine-encapsulated Fe3[Co(CN)6]2 NCs at 700 °C. Besides the comparable catalytic activity for oxygen reduction reaction (ORR) to the Pt/C catalyst, it showed much more outstanding catalytic selectivity and superior durability.