Ge-Doped RuO₂ for Stable and Active Acidic Oxygen Evolution Reaction

Proton exchange membrane water electrolysis is promising for green hydrogen production, but the sluggish oxygen evolution reaction (OER) and the poor stability of iridium-free OER electrocatalysts hinder its application. Herein, non-metallic element germanium (Ge) is doped into rutile RuO₂ nanoparticles to synthesize an active and stable Ru-based acidic OER electrocatalyst. The optimized catalyst (Ge_0.1Ru_0.9O₂) exhibits an ultralow overpotential of 161 mV at 10 mA cm^-2 and undergoes a long-term stability test of 650 h at 100 mA cm^-2, with a decay rate of 0.164 mV h^-1. The high performance is attributed to the isomorphic substitution of Ge, which possesses a slightly smaller ionic radius (53 pm) than Ru (64 pm) and the same valence state (4+), and can donate electrons to Ru, and enhance the structural stability. In situ attenuated total reflection-surface enhanced infrared absorption spectroscopy (ATR-SEIRAS), operando isotropic differential electrochemical mass spectrometry (DEMS), and first-principles calculations reveal that, compared to pristine RuO₂, the Ge dopants further unexpectedly facilitate water dissociation and accumulate abundant ─OH group as reactants on electrocatalysts surface. This work gives insights to non-metallic cation doping and interfacial water dissociation for the design of active and robust Ru-based electrocatalysts for acidic water splitting.