Ru-embedded TiO2-x with rich Ru-Ti bonds and triggered oxygen vacancies for boosted and sustained hydrogen oxidation and evolution electrocatalysis in alkaline medium

[Display omitted] •RuSA-RuNC/TiO2-x, a novel catalyst featuring ultrafine Ru clusters and single atoms confined within the TiO2-x lattice, is first developed.•RuSA-RuNC/TiO2-x exhibits bifunctional activity toward HOR and HER in a wide potential range.•High-density Ru-Ti interfacial bonds are shown to markedly boost the HOR/HER performance.•Triggered oxygen vacancies-Ti3+ during the electrochemical reaction function as auxiliary protectors. The sluggish hydrogen energy conversion kinetics in alkaline medium and the complete passivation under high anodic potential as well as the easy detachment of active sites from the carbon substrate are three critical challenges of Ru-based electrocatalysts for their practical application. Herein, Ru (single atoms and nanoclusters)-embedded TiO2-x (RuSA-RuNC/TiO2-x) well solves above-mentioned urgent problems simultaneously. Specifically, the optimal RuSA-RuNC/TiO2-x electrocatalyst delivers a mass activity of 1620 A gRu–1 and a low overpotential of 24 mV at 10 mA cm−2 in alkaline hydrogen oxidation and evolution reactions (HOR/HER), respectively. More importantly, the Ru/TiO2-x can unprecedentedly catalyze the HOR up to a potential of 1.2 V vs. RHE without deactivation and almost maintain unchanged after accelerated stability tests of 10,000 CVs or the presence of 100 ppm CO impurity. Confirmed by in/ex-situ experimental measurements and computational analyses, the enhancement in performance is attributed mainly to the construction of high-density Ru-Ti bonds, maintaining the unblocked charge transfer from TiO2 to Ru and achieving more low-valence Ru species. The observed Ti3+ species on oxygen vacancies derived from the original structure and in-situ formation during the electrochemical reaction would be preferentially oxidized, further protecting Ru sites and aiding in the electrocatalytic process. Benefiting from Ru-Ti bonds and triggered oxygen vacancies, Ru could serve as exclusive optimal H adsorption sites and cooperate with the OHad on Ti sites, rapidly and stably accelerating hydrogen energy conversion.