Optimizing cobalt/nickle sulfide heterojunction interface with ordered porous framework for efficient rechargeable zinc-air batteries

Developing efficient oxygen evolution/reduction reaction (OER/ORR) bifunctional catalysts is essential to improve zinc-air batteries (ZABs) performance. In this study, an OER/ORR bifunctional catalyst consists of cobalt and nickel sulfide heterojunction with three-dimensional ordered mesoporous structure is fabricated (3DOM Co ₉S ₈/Ni ₃S ₄). In-situ attenuated total reflection Fourier transform infrared tests and theoretical calculations reveal that the heterojunction structure promotes electrons transfer from Co ₉S ₈ to Ni ₃S ₄ and modulates the d-band center, thus optimizing the adsorption/desorption of *OH, *O and *OOH oxygen-containing intermediates and contributing to the improvement of the reactivity of the catalyst. In-situ Raman analysis shows that 3DOM Co ₉S ₈/Ni ₃S ₄ undergoes surface reconstruction to form highly reactive NiOOH species during the OER process. Meanwhile, the 3DOM framework structure also increases the catalyst specific surface area and benefits the mass transfer process during the reactions. As a result, 3DOM Co ₉S ₈/Ni ₃S ₄ exhibits a low OER overpotential (334 mV) at 10 mA cm ⁻² and the ORR half-wave potential is 0.77 V vs. RHE. The rechargeable ZABs with 3DOM Co ₉S ₈/Ni ₃S ₄ cathode deliver an energy density of 760.73 mAh g ⁻¹ at 10 mA cm ⁻² and stable cycling performance for 100 hours. This study provides guidance for developing efficient heterojunction bifunctional catalysts for ZABs.