Tailored Bond Heterogeneity through High-Entropy Doping for Efficient Acidic Water Oxidation.

Ru-based catalysts are promising alternatives to Ir for the oxygen evolution reaction in proton exchange membrane water electrolysis, yet their practical deployment is hindered by rapid dissolution in acidic environments. Conventional elemental doping microscopically improves stability through localized Ru-O-dopant interactions but fails to stabilize undoped regions, while high-entropy materials provide macroscopic structural robustness at the cost of active-site dilution. Here, we introduce a high-entropy doping (HED) strategy that integrates multiple foreign elements at the atomic dopant level to achieve both atomic-scale and lattice-scale stabilization. The resulting Ru-O bond heterogeneity microscopically optimizes the electronic structure of active Ru sites toward catalytic optimality, while multiaxial lattice distortion enhances macroscopic structural integrity and suppresses dissolution. The optimized HED1/RuO2 delivers long-term durability with a stability number (S-number) of 2.4 × 106, approaching IrO2 benchmarks.