Sustained Hydrogen Spillover on Ru/MXene Electrocatalysts for Highly Efficient Alkaline Hydrogen Evolution

Abstract

Developing high-performance noble metal electrocatalysts with accelerated water dissociation and proton transport kinetics under alkaline conditions is critical for scalable green hydrogen production. Herein, we report a Ru@SC‑Ti3C2Tx electrocatalyst constructed via a green and novel supercritical CO2‑mediated solid‑phase etching strategy, which exhibits exceptional HER performance under alkaline conditions. Supercritical CO2, serving as a green solvent, leverages its exceptional penetrability and mass-transfer properties to deliver solid fluoride molecules into the interlayers of MAX phases, enabling selective etching of Al layers under entirely solvent-free conditions. Subsequent loading of ultrafine Ru nanoclusters onto this functionalized MXene support affords the formation of the Ru@SC‑Ti3C2Tx heterostructure electrocatalyst. The optimal catalyst achieves an overpotential of only 14 mV at 10 mA cm−2 in 1 M KOH, with a Tafel slope of 31.5 mV dec−1, and exceptional stability (over 60 h at 100 mA cm−2), outperforming commercial Ru/C (10%) and Pt/C (20%). Operando Raman spectroscopy, electrochemical kinetic analysis, and density functional theory calculations collectively reveal a unique hydrogen spillover mechanism: Ru nanoclusters serve as efficient water dissociation centers, while the SC‑Ti3C2Tx surface acts as an efficient H* acceptor and reservoir, promoting interfacial H* migration. This spatial decoupling of HER elementary steps (H2O activation → H* recombination) synergistically enhances electrochemical reaction kinetics.