Nickel Foam‐Supported CoCO₃@CoSe Nanowires with a Heterostructure Interface for Overall Water Splitting with Low Overpotential and High Efficiency

The development of highly efficient and stable bifunctional catalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is important for the practical application of water splitting technologies. Herein, heterostructured Co(CO 3 ) 0.5 (OH)·0.11H 2 O@CoSe nanowire arrays supported on nickel foam (CCH@CoSe/NF) are successfully fabricated using a simple and facile two‐step hydrothermal method as efficient bifunctional catalysts for overall water splitting in alkaline media. The optimized CCH@CoSe/NF catalytic electrode exhibits an excellent OER activity with a low overpotential of 255 mV at 10 mA cm −2 and superior stability and HER activity with a low overpotential of 128 mV at 10 mA cm −2 and superior stability after 1000 cyclic voltammetry cycles. The defect‐rich heterojunction structure of the catalyst and the NF substrate are helpful to enhance the catalytic activity of a catalyst and the electron migration ability. Significantly, the cell based on bifunctional CCH@CoSe/NF//CCH@CoSe/NF electrodes shows highly efficient overall water electrolysis with a low potential of 1.638 V at 10 mA cm −2 in an alkaline electrolyte and maintains a good stability, indicating that the as‐prepared CCH@CoSe/NF electrodes show a promising potential in the practical overall water splitting electrocatalysis.