Oxygen Vacancy-Mediated Hetero-Asymmetrical Dual Active Sites Break the Activity-Stability Trade-Off for Efficient Acidic Water Oxidation

Regulating the reaction pathway to overcome the activity-stability trade-off of catalysts is significant but remains highly challenging in acidic oxygen evolution reactions (OERs). Herein, we incorporated atomically dispersed Ru into an oxygen vacancy-rich (Ovc) MnO2-x host through a combination of hydrothermal reaction, argon-plasma bombardment, and isomorphic substitution, resulting in a distinctive catalyst (Ru-AP-MnO2-x) featuring Ovc-mediated heteroasymmetric dual-active-site Mn-Ovc-Ru units. Impressively, the Ru-AP-MnO2-x catalyst achieved a low overpotential of 233 mV at 100 mA cm-2 and demonstrated an exceptional stability for >5000 h at 10 mA cm-2 in 0.5 M H2SO4. When used in a proton exchange membrane water electrolyzer (PEMWE), it required a potential of only 1.76 V to reach 3 A cm-2 (surpassing the DOE 2026 target: 1.8 V at 3 A cm-2) and operated stably at 1 A cm-2 for up to 2200 h with an extremely low potential decay rate of only 22.3 μV h-1, positioning it among the top-ranked Ru/Ir-based catalysts. Operando characterizations and theoretical calculations demonstrated that enhanced Ru-O covalency and reduced Ru-Mn distance in the unique Mn-Ovc-Ru unit enabled a heteroasymmetrical-dual-active-site-assisted lattice oxygen mechanism (HADAS-LOM) for OER, where the *O intermediates transferred from Ru to Mn sites coupled lattice O (Olat) for rapid O2 release. Moreover, the bridged Ovc increased the electron density at Ru sites to mitigate overoxidation, while synergistic Ru-Mn dual sites allowed Olat around Mn instead of Ru sites to form an *OO intermediate, effectively protecting Ru from dissolution. This work offers a blueprint for engineering Ovc and multiple active-site synergy in the design of acid-stable, high-efficiency OER electrocatalysts.