Growth of Lattice Coherent Co9S8/Co3O4 Nano‐Heterostructure for Maximizing the Catalysis of Co‐Based Composites

Gas purging during electrodeposition has significant influence on microstructures and compositions of materials. Co−Mn LDH was electrodeposited on Ni foam without gas purging. In contrast, the product grown by electrodeposition with N2 purging changes to Co9S8/Co3O4 heterostructure with the assistance of annealing. This remarkable distinction is mainly due to the decrease of concentration of hydroxide ions (produced by the reduction of NO3−) near electrode surface where the ion transport is remarkably enhanced by N2 purging. The heterostructure has shown superior performance for water splitting, especially for oxygen evolution reaction (OER). The 250 mV overpotential (@ 10 mA ⋅ cm−2) and 73.54 mV ⋅ dec−1 Tafel slope required for OER are lower than that of the state‐of‐the‐art Co‐based composites. It has also demonstrated excellent durability in alkaline media indicating its promising potential for practical application in industry. Controllable synthesis of lattice coherent Co9S8/Co3O4 nano‐heterostructure as highly efficient bifunctional electrocatalyst for water splitting in alkaline media: (a) HRTEM images (inset is the FFT pattern of the square region); (b) Inverse FFT (IFFT) image; (c) comparison of HER performance (inset is the corresponding EIS spectrum); (d) Comparison of OER performance