Quasi-Two-Dimensional Intermetallic Electride CeRuSi for Efficient Alkaline Hydrogen Evolution

Electrides are emerging catalyst materials, in which excess electrons serve as periodic anions. Although they have been successfully used for various hydrogenation reactions, due to weak chemical stabilities, their applications in aqueous systems remain challenging. Herein, we develop a quasi-two-dimensional (2D) intermetallic electride CeRuSi as a high-performance alkaline hydrogen evolution electrocatalyst, realizing an ultralow over potential of 28 mV at a current density of 10 mA/cm(2 )and longterm stability in 1.0 M KOH. The rate-determining step is deduced to be the Tafel step with accelerated kinetics. We show that CeRuSi is so far the best electride-based electrocatalyst for hydrogen evolution. We further demonstrate that high activity is mainly ascribed to the unique electride features and the coordinatively unsaturated Ru sites, exposed and activated via selective chemical etching. Finally, we confirm the superior catalytic performance using density functional theory calculations and find an optimized H adsorption energy over the Ru active centers. This work will stimulate more electrocatalytic studies on electrides and provide guidance for the design of electrocatalysts.