Modulating the Intrinsic Electrocatalytic Activity of Copper Sulfide by Silver Doping for Electrocatalytic Overall Water Splitting

Abstract Highly efficient and cost‐effective electrocatalysts towards bifunctional oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are critical for industrial scale and environmentally friendly electrocatalytic production. Herein, we attempt to synthesize a low‐cost copper sulfide bifunctional electrocatalyst and modulated the intrinsic electrocatalytic activity by silver doping at desired amounts by a facile chemical bath deposition technique. The intrinsic activity of the CuS by Ag doping was closely monitored and presented with detailed OER and HER electrochemical characterizations. Finally, the optimized overall water splitting electrolyzer with a doping level of Ag 10 % exhibited a relatively low cell voltage of 1.55 V at a current density of 10 mA/cm 2 . The surface having Ag 1+ and Cu 1+ oxidation states could effectively fetch electrons from OH − species leading to higher intrinsic activity. The stability of the best electrocatalyst checked up to 40 hours at a high current rate of 200 mA/cm 2 and shows a stable oxidation state. This work provides an important Ag doping strategy for bifunctional electrocatalyst to enhance their intrinsic catalytic activity for overall water splitting application.