Polarized Ru-HxWO3 Interface Drives Interfacial Water Restructuring for Accelerated Neutral Hydrogen Evolution

The electrocatalytic hydrogen evolution reaction (HER) in neutral media is fundamentally limited by sluggish water dissociation. Here we report a Ru single-atom catalyst supported on hydrogen tungsten bronze (Ru─H x WO 3 ) and show that its high activity originates from strong metal–support interaction (SMSI) at the Ru─O─W interface. The strong Ru-support coupling induces pronounced interfacial polarization, which restructures the local hydration layer and enriches activation-relevant interfacial water configurations for the Volmer step. As a result, Ru─H x WO 3 achieves an ultralow overpotential of 14 mV at 10 mA cm −2 , delivers a high Ru mass activity of 11.09 A mg Ru −1 at 100 mV, and sustains stable HER operation for 80 h at 1 A cm −2 in neutral media. This work elucidates a complete mechanistic pathway, demonstrating how strong Ru-support coupling leverages interfacial electronic modulation to dynamically control hydration-layer structure, thereby accelerating HER kinetics in neutral media.