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The application of heteroatom doped cobalt (Ni@Co/C) prepared from a porous metal–organic framework as the cathode material for the rechargeable zinc–air batteries has been demonstrated. The Ni@Co/C‐modified electrode showed an excellent catalytic activity toward oxidation–reduction reaction and oxygen evolution reactions. The Co/C catalysts, which were Co particle impregnated on graphitic carbon powders, were synthesized after the calcination of Co3 (SDA)3(DMF)2 precursor, and then Ni deposition (Ni@Co/C) was followed on it by chemical reduction. Linear sweep voltammetry measurement indicates that Ni@Co/C‐H800, which had Ni particles on Co/C derived from MOF at 800 °C under N2, exhibited excellent performance. The stable charging/discharging profiles at 20 mA cm−2 of current were obtained for the 350 h in alkaline medium, suggesting Ni@Co/C‐H800 as a potential candidate for oxidation–reduction and evolution reactions. [ABSTRACT FROM AUTHOR]

A metal–organic framework (MOF) was synthesized using 4,4′‐stilbenedicarboxylic acid (H2SDA) in dimethylformamide (DMF). Carbon‐coated Co (C@Co) catalysts were prepared by the direct calcination of Co3(SDA)3(DMF)2 MOF crystals at various temperatures. The highest surface area of the C@Co catalyst is obtained at 600 °C which can further be increased by the ball mill operation. The X‐ray photon spectroscopy and X‐ray diffraction analysis proved the formation of metallic Co in the carbon matrix at temperatures over 500 °C, while Co3O4 formation was observed at 500 °C. Furthermore, the graphitic properties of the Co particles were analyzed by Raman spectroscopy. The durability of the carbon‐coated Co catalysts derived from MOFs (C@Co catalysts) was analyzed by the cycle test (charge/discharge at 20 mA/cm2 per 2 h) and was retained over 350 h. These catalysts showed remarkable stability for both ORR (oxygen reduction reaction) and OER (oxygen evolution reaction), comparable to that of Co3O4 and Co metal powder in alkaline solution. [ABSTRACT FROM AUTHOR]

[Display omitted] • Highly porous carbon network was derived from zeolitic-imidazole frameworks. • Co-deposition on porous carbon enhanced the catalytic activity. • Co on carbon was electrochemically stable as cathode material during 520 h cycling. Porous carbon wrapped on cobalt catalyst is one of the promising candidates to replace noble metal-based catalysts for ORR. Herein, a porous carbon network (PCN) was obtained by synthesis of zeolitic-imidazole frameworks (ZIF-8) followed by pyrolysis at 1050 ℃ under a nitrogenous atmosphere and the cobalt (Co) was deposited on PCN to obtain Co-PCN by sequential reduction method. The PCN showed a relatively high specific surface area of 806.43 m2/g and decreases to 329.4 m2/g with the introduction of Co contents in PCN. The Co-PCN reveals excellent performance having a current density of 350 mA cm−2 for the ORR at 0.5 V after 20th cycles as a cathode material in rechargeable zinc-air batteries. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fabrication of nickel-cobalt nanocage for oxygen evolution reactions. • Excellent oxygen evolution reaction performance with overpotential of 350 mV. • Synergic effect of cobalt-nickel catalyst improves the conductivity and charge transfer. The development of efficient, eco-friendly, and inexpensive electrocatalysts has become crucial and significant in water-splitting applications. Herein, we developed a nickel-cobalt nanocage (Ni/Co-NC) electrocatalyst via the solvothermal method which can boost the performances towards oxygen evolution reactions (OER) and hydrogen evolution reactions (HER). The Ni/Co-NC reveals significant performance at an onset potential of 350 mV for the OER at a delivered current density of 10 mA cm−2. The significant amount of oxygen vacancies generated by the addition of nickel in cobalt has been verified by XPS and the nanocage structure revealed by TEM and SEM images helps in effective performance for OER/HER. Furthermore, the synergistic effect between various Ni3+/Ni2+ and Co2+ could optimize the performance resulting in a smaller Tafel slope of 70 mV dec−1 for Ni/Co-NC. [ABSTRACT FROM AUTHOR]