Single-Atom Ru-Triggered Lattice Oxygen Redox Mechanism for Enhanced Acidic Water Oxidation

Activating the oxygen anionic redox presents a promising avenue for developing highly active oxygen evolution reaction (OER) electrocatalysts for proton-exchange membrane water electrolyzers (PEMWE). Here, we engineered a lattice-confined Ru single atom dispersed on a lamellar manganese oxide (MnO₂) cation site. The strong Ru-O bond induced an upward shift in the O 2<i>p</i> band, enhancing metal-oxygen covalency and reshaping the OER mechanism toward lattice oxygen oxidation pathway with increased activity. <i>In situ</i> spectral characterization combined with density functional theory (DFT) calculations revealed that electron transfer from Mn to Ru alleviates the Jahn-Teller effect within the MnO₆ octahedral structure, stabilizing the lattice. The layered Ru/MnO₂ architecture also promotes the rapid replenishment of oxygen vacancies, preventing structural collapse. As a result, the optimized Ru/MnO₂ electrocatalyst achieves an OER overpotential of only 179 mV at 10 mA cm^-2 in 0.5 M H₂SO₄, along with exceptional durability over 1000 h at 100 mA cm^-2. Moreover, the Ru/MnO₂-based PEM device requires only 1.71 V to reach 1 A cm^-2 and shows a durability of 500 h at 500 mA cm^-2.