Stabilizing Lattice Oxygen Mechanism on Ru Single Atoms via a High-Entropy Support for Acidic Oxygen Evolution

The lattice oxygen mechanism (LOM) has emerged as an effective route to enhance acidic oxygen evolution reaction (OER) activity. However, extensive lattice-oxygen participation often leads to defect accumulation and framework destabilization, severely limiting catalyst durability. Herein, we propose that anchoring Ru single atoms on a high-entropy oxide (Ru-(FeCoNiCrMn) 3 O 4 ) establishes a stabilized LOM pathway at the Ru sites, combining high activity with long-term structural integrity. The high-entropy effect strengthens Ru 4d-O 2p hybridization, lowering the energetic barrier for lattice-oxygen oxidation and facilitating direct O lat –O ad coupling between lattice oxygen near the Ru sites and adsorbed oxygen species. In parallel, disruption of the interfacial hydrogen-bond network enriches weakly hydrogen-bonded free water with high reactivity, enabling rapid incorporation of water-derived oxygen into lattice-oxygen defects. This dynamic defect-refilling process preserves the local coordination environment of Ru sites and prevents irreversible structural degradation. Consequently, the Ru-(FeCoNiCrMn) 3 O 4 catalyst only needs an overpotential of 204 mV to reach 10 mA cm –2 in 0.5 M H 2 SO 4 and delivers a high mass activity of 5235.42 A g Ru –1 at 1.50 V vs RHE. The proton exchange membrane electrolyzer with a Ru-(FeCoNiCrMn) 3 O 4 anode can operate stably for over 320 h at 500 mA cm –2 . This work presents a novel strategy for simultaneously enhancing catalyst activity and stability.