Hierarchical Nickel–Cobalt Dichalcogenide Nanostructure as an Efficient Electrocatalyst for Oxygen Evolution Reaction and a Zn–Air Battery

[Image: see text] A unique three-dimensional (3D) structure consisting of a hierarchical nickel–cobalt dichalcogenide spinel nanostructure is investigated for its electrocatalytic properties at benign neutral and alkaline pH and applied as an air cathode for practical zinc–air batteries. The results show a high oxygen evolution reaction catalytic activity of nickel–cobalt sulfide nanosheet arrays grown on carbon cloth (NiCo(2)S(4) NS/CC) over the commercial benchmarking catalyst under both pH conditions. In particular, the NiCo(2)S(4) NS/CC air cathode shows high discharge capacity, a narrow potential gap between discharge and charge, and superior cycle durability with reversibility, which exceeds that of commercial precious metal-based electrodes. The excellent performance of NiCo(2)S(4) NS/CC in water electrolyzers and zinc–air batteries is mainly due to highly exposed electroactive sites with a rough surface, morphology-based advantages of nanosheet arrays, good adhesion between NiCo(2)S(4) and the conducting carbon cloth, and the active layer formed of nickel–cobalt (oxy)hydroxides during water splitting. These results suggest that NiCo(2)S(4) NS/CC could be a promising candidate as an efficient electrode for high-performance water electrolyzers and rechargeable zinc–air batteries.