Ultralow Ru Loading on Spinel Oxide Enhances Oxygen Coupling for Efficient Acidic Water Oxidation

The development of proton-exchange membrane water electrolysis (PEMWE) technologies urgently demands electrocatalytic systems capable of maintaining exceptional activity and durability under harsh acidic oxygen evolution reaction (OER) conditions. Here, we present ultralow Ru loading on cobalt–manganese oxides (Ru–Co 2 MnO 4.5 ) through a facile synthetic strategy. Ru and Co sites facilitate the direct coupling of the oxygen radicals, thereby exceeding the limitations of the scaling relation and triggering the oxide pathway mechanism. Structural characterizations and theoretical calculations demonstrate that the incorporation of Ru single atoms suppresses both lattice oxygen and metal dissolution while maintaining good coordination environments and crystal structures. Furthermore, Ru single-atom loading enhances the hydroxyl adsorption on the catalyst surface and promotes the OER kinetics. Consequently, the Ru–Co 2 MnO 4.5 catalyst achieves an optimal trade-off between catalytic efficiency and structural durability. In 0.5 M H 2 SO 4, the Ru–Co 2 MnO 4.5 demonstrates a minimal overpotential of 176 mV at 10 mA cm –2 and exhibits excellent stability during 600 h. In the PEMWE device, the Ru–Co 2 MnO 4.5 catalyst requires merely a voltage of 1.638 V to achieve 1 A cm –2, with an ultralow Ru loading of 20 μg cm –2 . The system can operate for over 100 h under a high current density of 1 A cm –2, showcasing its potential in a practical hydrogen production device. This work presents an innovative strategy for advancing the development of high-efficiency and large-scale green hydrogen production systems while elucidating the underlying reaction mechanisms.