Asymmetric Charge Redistribution at the Tri-Functional Cu₁–Ru/CeO_x Interface Enables Alkaline Hydrogen Evolution Reaction

Abstract

The development of efficient electrocatalysts for the alkaline hydrogen evolution reaction (HER) remains a key challenge for hydrogen energy conversion. Here, we report a Cu-substituted Ru nanoparticle catalyst in which atomically dispersed Cu (0.31 wt%) is substituted into Ru nanoparticles (3.54 wt%) supported on oxygen-deficient ceria (Cu₁–Ru/CeO_x). This catalyst exhibits outstanding alkaline HER performance, delivering a low overpotential of 47 mV at 10 mA cm⁻², a small Tafel slope of 43 mV dec⁻¹, and a high mass activity exceeding 3.0 A mg_Ru^-1, outperforming commercial Pt/C. The catalyst retains 95% of its initial activity after 100 h of continuous operation. Spectroscopic, structural, and DFT analyses reveal an asymmetric interfacial charge distribution: charge transfer from Cu to Ru generates electron-rich Ru and electron-deficient Cu₁, while electron donation from Ru to ceria forms Ce³⁺ and oxygen vacancies. This tri-functional interface enables efficient water dissociation at Ce³⁺–O_v sites, optimized hydroxyl adsorption/desorption on electron-rich Ru, and weakened H binding on electron-deficient Cu₁, thereby promoting H₂ release. When paired with a RuO₂ anode, the Cu₁–Ru/CeO_x(−)║RuO₂(+) electrolyzer surpasses Pt/C(−)║RuO₂(+) in full-cell efficiency and long-term stability, highlighting the importance of interfacial charge modulation and multi-site cooperativity in alkaline HER catalysis.

Keywords

alkaline hydrogen evolution reaction / Cu₁-substituted Ru nanoparticles / interfacial charge modulation / oxygen-deficient ceria / tri-functional active sites

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