Highly efficient overall water splitting over a porous interconnected network by nickel cobalt oxysulfide interfacial assembled Cu@Cu₂S nanowires

The development of highly efficient electrocatalysts for simultaneous evolution of hydrogen and oxygen is a vital concern in water splitting. In this study, a novel catalyst derived from a porous interconnected network of nickel cobalt oxysulfide interfacial assembled Cu@Cu2S nanowires was rationally designed. It was recognized that the formation of multi-integrated active centers and a higher number of active sites, together with an adjusted adsorption energy towards reactants caused by the modulated surface and crystalline distortion of the NiCo oxide layer due to S insertion synergistically promoted both HER and OER. In addition, such 3D innovative core-shell structure effectively fine-tuned conductive properties and maximized interfacial contact to improve charge/mass transfer, thereby boosting catalytic activity and durability towards hydrogen and oxygen evolution. The catalyst only required an overpotential of 203 mV to achieve a current response of 20 mA cm-2 for the HER and 295 mV to reach 50 mA cm-2 for the OER in 1.0 M KOH medium. A developed electrolyzer enabled a small cell voltage of 1.61 V at 20 mA cm-2 without performance decay upon long-term operation. This result suggested an exciting prospect for developing new bifunctional electrocatalysts, which could effectively accelerate both hydrogen and oxygen evolution for water splitting applications.