Suppression of Oxygen Vacancies in Rutile Ruo2 via In Situ Exsolution for Enhanced Water Electrocatalysis

Elemental vacancies are proposed as an effective approach to tuning the electronic structure of catalysts that are critical for energy conversion. However, for reactions such as the sluggish oxygen evolution reaction, the excess of oxygen vacancies (VO) is inevitable and detrimental to catalysts’ electrochemical stability and activities, e.g., in the most active RuO2. While significant work is carried out to hinder the formation of VO, the development of a fast and efficient strategy is limited. Herein, a protection SrO layer produced successfully at the surface of RuO2 with the in situ exsolution method with perovskite SrRuO3 as the precatalyst, which could significantly hinder the generation of VO. Benefited from the suppression of VO, the surface‐modified RuO2 requires a low overpotential of 290 mV at 100 mA cm−2, accompanied by remarkably high electrochemical stability (100 h) and Faraday efficiency (≈100%). Theoretical investigation reveals that the formation energy of VO in RuO2 is almost doubled in the exsolved RuO2 phase as a result of the weakened RuO bond covalency. This work not only provides insight into the structural evolution of perovskite oxide catalysts but also demonstrates the feasibility of controlling vacancy formation via in situ exsolution.