Regulating Crystal Phase in Ir-Ge Interstitials for Hydrogen Evolution Electrocatalysis

The exploration of new catalysts and identification of crucial active sites are of great significance to the field of energy conversion and storage. Here, we report the phase-selective synthesis of three interstitial Ir-Ge electrocatalysts: IrGe, Ir3Ge7, and Ir4Ge5. The IrGe catalyst possesses the appropriate d–sp orbital hybridization, which activates the Ge site with optimal hydrogen adsorption energy. In situ electrochemical experiments and density functional theory calculations reveal a hydrogen spillover effect by which the H* formed on Ir sites transfers to the Ge sites in IrGe, resulting in activated Ge sites with outstanding catalytic activity. As a result, IrGe exhibits an ultralow overpotential of 12 mV at 10 mA cm–2 for the hydrogen evolution reaction (HER) under acidic conditions, outperforming Pt and other reported Ir-based catalysts. This work not only provides an alternative strategy for the design of new catalysts but also lays a foundation for the identification of catalytic active sites.