Dual-Modulation Strategy in RuO x Improves Activity and Durability in Acidic Oxygen Evolution

Durable oxygen evolution catalysts are needed for proton-exchange-membrane water electrolyzers (PEMWEs) for hydrogen production. Ruthenium-based oxides offer high activity in acids but suffer from instability under oxidative conditions. Here, we study a dual-modulation approach intended to improve activity and durability together: we couple two functionally distinct dopants, one redox-active dopant that buffers metal overoxidation and one lattice-stabilizing dopant that suppresses structural degradation. This strategy, studied using operando spectroscopy, isotope labeling, and density functional theory, provides a cooperative suppression of Ru overoxidation and lattice breakdown. Implemented in a Ru–Mn–Ti oxide system, the optimized composition, Ru0.7Mn0.1Ti0.2Ox, reaches 143 mV overpotential at 10 mA cm–2 and enables a proton exchange membrane water electrolyzer device to operate for 800 h at 1 A cm–2 and 1.66 V with a degradation rate of 0.2 mV h–1. The approach may be useful for designing other multimetal oxide catalysts. We note that 800 h is short compared to the lifetimes that commercial electrolyzers require, so this work is one contribution along a longer community path rather than a demonstration of commercial durability.