Rare Earth Dilute Alloys Unlock Fast Water Dissociation for Alkaline Hydrogen Evolution
Ruthenium (Ru)-based alloys are promising alternatives to commercial Pt/C catalysts for the hydrogen evolution reaction (HER) owing to their low cost and favorable hydrogen adsorption properties. However, the sluggish water dissociation on Ru catalysts remains a major kinetic bottleneck in alkaline solutions. Herein, we report a rare earth (RE) dilute alloy strategy by incorporating a trace amount of cerium (Ce, ~1 at%) into a RuCu alloy to promote interfacial water activation. The oxophilic Ce sites strengthen H2O adsorption and reduce the energy barrier for water dissociation, thereby accelerating the Volmer step during alkaline hydrogen evolution. Consequently, the RuCuCe catalyst delivers 10 mA cm−2 at an overpotential of only 18 mV in 1.0 M KOH and maintains stable operation for over 100 h at 500 mA cm−2 in a membrane electrode assembly. In situ electrochemical impedance spectroscopy and pH-dependent measurements verify the facilitated Volmer process induced by Ce incorporation. Temperature-dependent analysis further shows that the apparent activation energy decreases from 47.4 kJ mol−1 for RuCu to 26.4 kJ mol−1 for RuCuCe, consistent with enhanced water dissociation kinetics. This work establishes RE dilute metal alloys as an effective platform for boosting the intrinsic activity of Ru-based alloy catalysts, in which RE incorporation promotes water dissociation while inducing charge redistribution in the alloy matrix.