Octahedral Ru Centers Modulate Lattice Covalency and Interfacial PCET for Stable Acidic Oxygen Evolution

ABSTRACT Developing active and durable catalysts for acidic oxygen evolution reaction (OER) is critical for proton‐exchange membrane water electrolysis (PEMWE). However, it remains challenging because highly active oxides often undergo over‐oxidation and structural degradation under anodic conditions. In this study, we report a Ru‐modified CoMn spinel catalyst in which highly oxyphilic Ru is anchored at octahedral sites to regulate both the lattice electronic structure and the interfacial reaction environment. The strong Ru‐O covalency and pronounced oxygen‐hole character enhance the OER kinetics. Meanwhile, the highly polarized Ru centers reconstruct the interfacial hydrogen‐bond network and accelerate interfacial proton‐coupled electron transfer (PCET). The introduction of Ru can maintain structural stability during OER through restraining excessive Co oxidation and local coordination changes. As a result, Ru‐MnCo 2 O x catalyst exhibits an overpotential of 203 mV at 10 mA cm −2 with over 500 h stability in acid. The Ru‐MnCo 2 O x ||Pt/C PEMWE device shows a cell voltage of 1.68 V@1.0 A cm −2 , which is much lower than that of commercial RuO 2 ||Pt/C PEMWE device (2.1 V@ 1 A cm −2 ). Moreover, the Ru‐MnCo 2 O x ||Pt/C can be operated steadily at 0.5 A cm −2 over 300 h.