Hydrogen spillover in complex oxide multifunctional sites improves acidic hydrogen evolution electrocatalysis.

Improving the catalytic efficiency of platinum for the hydrogen evolution reaction is valuable for water splitting technologies. Hydrogen spillover has emerged as a new strategy in designing binary-component Pt/support electrocatalysts. However, such binary catalysts often suffer from a long reaction pathway, undesirable interfacial barrier, and complicated synthetic processes. Here we report a single-phase complex oxide La 2 Sr 2 PtO 7+δ as a high-performance hydrogen evolution electrocatalyst in acidic media utilizing an atomic-scale hydrogen spillover effect between multifunctional catalytic sites. With insights from comprehensive experiments and theoretical calculations, the overall hydrogen evolution pathway proceeds along three steps: fast proton adsorption on O site, facile hydrogen migration from O site to Pt site via thermoneutral La-Pt bridge site serving as the mediator, and favorable H 2 desorption on Pt site. Benefiting from this catalytic process, the resulting La 2 Sr 2 PtO 7+δ exhibits a low overpotential of 13 mV at 10 mA cm -2 , a small Tafel slope of 22 mV dec -1 , an enhanced intrinsic activity, and a greater durability than commercial Pt black catalyst.