Rational Design of a Copper Cobalt Sulfide/Tungsten Disulfide Heterostructure for Excellent Overall Water Splitting

Integrating different components into a heterostructure is a novel approach that increases the number of active centers to enhance the catalytic activities of a catalyst. This study uses an efficient, facile hydrothermal strategy to synthesize a unique heterostructure of copper cobalt sulfide and tungsten disulfide (CuCo₂S₄-WS₂) nanowires on a Ni foam (NF) substrate. The nanowire arrays (CuCo₂S₄-WS₂/NF) with multiple integrated active sites exhibit small overpotentials of 202 (299) and 240 (320) mV for HER and OER at 20 (50) mA cm^-2 and 1.54 V (10 mA cm^-2) for an electrolyzer in 1.0 M KOH, surpassing commercial and previously reported catalysts. A solar electrolyzer composed of CuCo₂S₄-WS₂ bifunctional electrodes also produced significant amounts of hydrogen through a water splitting process. The remarkable performance is accredited to the extended electroactive surface area, reasonable density of states near the Fermi level, optimal adsorption free energies, and good charge transfer ability, further validating the excellent dual function of CuCo₂S₄-WS₂/NF in electrochemical water splitting.