Enhancing the Catalytic Kinetics and Stability of Ru Sites for Acidic Water Oxidation by Forming Brønsted Acid Sites in Tungsten Oxide Matrix

Abstract The oxygen evolution reaction (OER) suffers from sluggish kinetics even on the benchmark RuO 2 catalyst, due to the complex four sequential proton‐coupled electron transfer steps. Severe electrochemical oxidation and dissolution issues also make RuO 2 fail as an alternative to highly expensive iridium‐based OER catalysts applied in proton exchange membrane water electrolysis. Herein, an acid‐stable W 18 O 49‐δ matrix‐confined Ru solid solution oxide is developed with considerably reduced Ru loadings beyond commercial RuO 2 , to enhance the acidic OER kinetics and extend the long‐term durability simultaneously by incorporating Brønsted acid sites. The representative Ru 0.6 W 17.4 O 49‐δ with 3D urchin‐like morphology achieves an excellent catalytic stability with ultra‐slow degradation rate and a high mass activity of 27 110 A g −1 Ru @ 1.53 V versus RHE in 0.1 m HClO 4 electrolyte, which is ≈10.8 times higher than that of commercial RuO 2 . The enhanced electron transfer from W to Ru during the OER process prevents the over‐oxidation of surface Ru sites extending the long‐term stability, while the incorporated Ru‐O bri ‐W Brønsted acid sites accelerate the deprotonation step by promoting the mobility of proton from the oxo‐intermediate to the neighboring O bri sites, thus boosting the acidic OER kinetics.