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Abstract: Nitrogen‐doped porous carbons have been well‐recognized as promising materials for a wide range of applications. Therefore, the rational design and synthesis of nitrogen‐doped porous carbons are essential both for practical applications as well as for understanding of their fundamental properties. In this Communication, we report a silica‐template‐assisted fabrication of nitrogen‐doped porous carbons through pyrolysis of polyelectrolyte brushes. The resulting material has a surface area of 799 m2 g−1 and exhibits improved electrochemical catalytic ability towards the oxygen reduction reaction in basic medium and an increased carbon dioxide adsorption capability compared with samples derived from a physical mixture of polyelectrolyte and silica, although the latter sample has higher overall nitrogen content. The findings in this work provide a new strategy to fabricate nitrogen‐doped porous carbon not only for practical applications, but also as a model system for fundamental understanding of the correlation between heteroatom distribution and properties. [ABSTRACT FROM AUTHOR]

Robust and efficient catalysts for the oxygen reduction reaction (ORR) are required for the development of various energy storage and conversion devices. In this study, a durable and high-performance Fe3C@graphene ORR catalyst has been developed by the carbonization of urea- and agar-modified Fe2O3 nanorods. The influence of the carbonization temperature and annealing time on the activity and stability of the resulting Fe/ C catalyst was studied in detail. The Fe/C catalyst synthesized at a temperature of 700°C (holding time: 60 min) showed better ORR activity and improved stability compared to a commercial Pt/C catalyst. The improved ORR catalytic activity of the catalyst is due to its high Fe3C content and its good durability results from the unique microstructure of the Fe3C@graphene hybrid. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) porous carbon-based materials with tunable composition and microstructure are of great interest for the development of oxygen involved electrocatalytic reactions. Here, we report the synthesis of 3D porous carbon-based electrocatalyst by self-assembling Co-metal organic frameworks (MOF) building blocks on graphene via a layer-by-layer technique. Precise control of the structure and morphology is achieved by varying the MOF layer to tune the electrocatalytic properties. The as-produced electrocatalyst exhibits an excellent catalytic activity for the oxygen reduction reaction in 0.1 mol L−1 KOH, showing a high onset potential of 0.963 V vs. reversible hydrogen electrode (RHE) and a low tafel slope of 54 mV dec−1, compared to Pt/C (0.934 V and 52 mV dec−1, respectively). Additionally, it shows a slightly lower potential vs. RHE (1.72 V) than RuO 2 (1.75 V) at 10 mA cm−2 in an alkaline electrolyte. A rechargeable Zn-air battery based on the as-produced 3D porous catalyst demonstrates a high peak power density of 119 mW cm−2 at a cell voltage of 0.578 V while retaining an excellent stability over 250 charge-discharge cycles. [ABSTRACT FROM AUTHOR]

[Display omitted] • Simple low-temperature etching of ZIF-67 generate crystalline-amorphous Co/Co 3 O 4. • ZIF@RGO-400 maintains a cubic structure with a high surface area of 900 m2/g. • ZIF@RGO-400 exhibits promising bifunctional catalytic activity for the ORR and OER. • Stability of ZIF@RGO-400 is greater than those of Pt/C and IrO 2 in zinc-air cells. Development of a simple method for synthesizing transition metal-based bifunctional catalysts is of great importance in the context of oxygen-involved electrochemical energy conversion and storage devices. In this effort, electrochemical catalysts consisting of amorphous cobalt and cobalt oxides on graphene oxide (GO) were fabricated using a solvothermal process followed by etching ZIF-67 with oxygen-rich functional groups on GO (≈ 29 at. %) in a weak reduction atmosphere at 400 ℃. During the calcination process forming the ZIF-67@GO-based materials, exposed cobalt metal centers are created by partial vaporization and oxidation of ZIF-67. Also, metal ions are reduced to form Co and partially combine with oxygen from GO to generate amorphous Co 3 O 4. Moreover, the porous framework structure of ZIF is retained under the mild calcination temperatures used. Benefiting from their porous framework and heteroatoms-doped composition, the ZIF-67@GO-based materials have low overpotentials of 319 mV at 10 mA cm−2 and high catalytic activities toward the oxygen evolution and oxygen reduction reactions in an alkaline electrolyte. In addition, the liquid zinc-air battery assembled with the ZIF-67@GO composite produced at a calcination temperature of 400 ℃ displays a high performance. Overall, the results demonstrate that the ZIF-67@GO composites have the potential to be high-performing catalysts in energy conversion devices. The readily controllable and high-yielding calcination method in this study is expected to serve as a model for new strategies to synthesize low-cost and efficient bifunctional electrocatalysts. [ABSTRACT FROM AUTHOR]

Design and synthesis of earth-abundant elements-based electrocatalysts with sufficient activity and stability remain challenging for oxygen-involved electrochemical energy conversion and storage devices. In this work, catalyst with simultaneously engineered Fe-N 4 and Co-N 4 active sites and graphitic carbon multilayer-encapsulated FeCo alloy is developed by pyrolysis of metal salts doped G-g-C 3 N 4. The obtained composite material exhibits promising catalytic activity and good stability for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in alkaline electrolyte, as evidenced by the positive shift of half-wave potential by 44 mV compared to 20% Pt/C for ORR and the potential of 1.596 V at current density of 10 mAcm−2 for OER. In addition, the thus-assembled rechargeable zinc-air battery using the synthesized material as cathode delivers a maximum power density of 311.2 mWcm−2 with an open circuit potential of 1.51 V and a long-term cycling stability. DFT calculation results indicate that catalyst with composite active sites displays smaller energy barrier than that with single active site. • Catalyst consisting of Fe/Co-N 4 sites and N-doped carbon with encapsulated FeCo alloy is formed. • The catalyst possesses promising bifunctional activity towards ORR and OER. • The catalyst outperforms Pt/C catalyst for ORR in alkaline electrolyte. • The assembled Zn-air battery has a peak power density of 120 mWcm−2 with OCV of 1.52 V. [ABSTRACT FROM AUTHOR]

Abstract: A novel non-Pt catalyst silver-molybdate electrocatalyst prepared by hydrothermal method was used for the oxygen reduction reaction (ORR) in alkaline solution for the first time. These silver-molybdate electrocatalysts showed catalytic activity for ORR and higher durability than Pt/C catalyst. Such catalyst with advantages including facile synthesis, low cost and good durability could be a valuable catalyst for oxygen reduction reaction and be a potential candidate for application in alkaline fuel cells and metal–air batteries. [Copyright &y& Elsevier]