Kehong Wang, Wei Zhao, Yao Dai, Yuge Cao, Zhangliu Tian, Yanli Liu, Fuqiang Huang
ABSTRACT Ruthenium‐based single‐atom catalysts (Ru‐SACs) are promising for the alkaline hydrogen evolution reaction (HER), but challenges like sluggish kinetics and poor stability limit their applications for high current water electrolysis (>500 mA cm −2 ). Herein, we develop a novel Ru–Eu dual single‐atom catalyst anchored on porous and conductive Magnéli‐phase Ti 4 O 7 (Ru/Eu@Ti 4 O 7 ) via selective etching and wet impregnation. Ru/Eu@Ti 4 O 7 exhibits a high specific surface area and metallic conductivity for efficient electrocatalytic HER. Europium incorporation significantly increases oxygen vacancies of Ti 4 O 7 induces lattice distortion, and modulates the electronical structure and coordination environment of Ru sites. Theoretical calculations indicate reduced adsorption strength of *H intermediate and decreased energy barrier of Ru/Eu@Ti 4 O 7 for HER. In situ Raman reveals enhanced water adsorption, dissociation, and intermediate desorption to accelerate the Volmer step in Ru/Eu@Ti 4 O 7 . Consequently, Ru/Eu@Ti 4 O 7 achieves exceptional HER performance with an overpotential of 29 mV at 10 mA cm −2 and a Tafel slope of 43 mV dec −1 in 1 m KOH and demonstrates impressive stability (>2000 h@1000 mA cm −2 @2.0 V) in a full electrolyzer with ultra‐low Ru mass loading (0.07 mg Ru cm −2 ). This study provides an effective strategy to construct noble metal based SACs with both high activity and high conductivity for large current water splitting.