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.