The rational design of Cu2−xSe@(Co,Cu)Se2 core–shell structures as bifunctional electrocatalysts for neutral-pH overall water splitting

Abstract

Highly active and stable bifunctional electrocatalysts for H₂ generation from neutral-pH water are desired, but difficult to achieve. The modification of the electronic and crystal structure of a material by element doping, morphology design and constructing a complex is a valid strategy for obtaining high-performance catalysts toward overall water splitting. In this study, a novel Cu_2−xSe@(Co,Cu)Se₂ core–shell structure with ultrathin (Co,Cu)Se₂ nanosheets anchored as a shell on an internal Cu_2−xSe core was fabricated, for the first time, by integrating the three above-mentioned modification methods. Benefiting from the synergistic effect between components and the unique structure, the Cu_2−xSe@(Co,Cu)Se₂ core–shell structure can serve as an efficient bifunctional electrocatalyst for both HERs and OERs in neutral-pH electrolytes with a current density of 10 mA cm⁻² at the overpotentials of 106 mV and 396 mV, respectively. Additionally, the material just requires a cell voltage of 1.73 V to afford a current density of 10 mA cm⁻² in a neutral two-electrode electrolyzer. Such performances significantly outperform control catalysts and analogues. Even more importantly, the original concept of coordinated regulation presented in this work can broaden our horizons in the design of new and highly efficient catalysts for neutral water splitting.