Bismuth Single‐Atom Decorated Crystalline/Amorphous Ru/RuO 2 Heterojunctions With Abundant Oxygen Vacancies for pH‐Universal Hydrogen Evolution Reaction

ABSTRACT Inhibiting the excessive oxidation of Ru, regulating the composition, and optimizing the electronic structure are the keys to achieving efficient hydrogen evolution reaction (HER) of Ru/RuO 2 heterojunctions over the full pH range, yet significant challenges remain. To address the existing challenges, oxophilic Bi single atoms (SA) were introduced into the Ru precursor and partially oxidized to construct Bi SA decorated amorphous/crystalline Ru/RuO 2 heterojunctions with abundant oxygen vacancies (Bi SA ‐Ru@RuO 2 ‐2%). The key innovation lies in the fact that Bi SA subtly reduces the formation energy of defective RuO 2 , restrains Ru over‐oxidation, and promotes the formation of amorphous/crystalline Ru/RuO 2 heterostructures. Moreover, Ru–O–Bi interfacial bonds trigger efficient charge redistribution, activating adjacent Ru active centers. Electron‐deficient RuO 2 enhances H 2 O adsorption and reduces the O–H bond cleavage barrier, while electron‐rich metallic Ru optimizes hydrogen adsorption Gibbs free energy, boosting intrinsic HER kinetics. Benefiting from these advantages, Bi SA ‐Ru@RuO 2 ‐2% exhibits exceptional HER activity in alkaline (15 mV), neutral (30 mV), and acidic (32 mV) media at 10 mA cm −2 , better than most reported noble metal electrocatalysts, along with outstanding long‐term stability over 500 h without obvious activity loss in alkaline seawater. This study contributes to a viable strategy for the rational design of high‐performance HER electrocatalysts through single‐atom modification and heterojunction engineering, as well as assists in developing efficient, stable, and versatile electrocatalysts for renewable energy conversion applications.