Copper-doped zinc cobalt sulfide nanosheets as advanced bifunctional electrocatalysts for sustainable hydrogen production via electrochemical water splitting

Heteroatom doping represents an innovative strategy for finely tuning a catalyst’s electronic structure and kinetics for efficient water splitting. We synthesized a novel electrocatalyst of copper-doped zinc cobalt sulfide nanosheets (Cu-ZnCoS/NF) via a hexamethylenetetramine-assisted hydrothermal process. The resulting catalyst exhibits exceptional performance, with minimal overpotentials for both the hydrogen evolution reaction (HER 119/217 mV) and the oxygen evolution reaction (OER 210/280 mV) at 20 and 50 mA cm⁻², respectively, in an alkaline environment. The water electrolyzer/anion–exchange membrane (AEM) electrolyzer containing Cu-ZnCoS/NF as both cathode and anode operate at a low voltage of 1.51 V/1.88 V, respectively, for several hours. The density functional theory (DFT) and electrochemical tests reveal that modulation of the electronic structure optimizes intermediate adsorption energy, enhances electroactive centers, and facilitates charge transfer of the water-splitting process. These findings pave the way for exploring similar catalysts as robust electrocatalysts for practical electrolyzer devices.