Accelerated Deprotonation Triggered by Fluorinated RuO₂ Enables Efficient and Stable Acidic Water Electrolysis

Ru-based catalysts are considered highly promising candidates for enabling cost-effective proton exchange membrane water electrolyzers (PEMWEs). However, under the harsh conditions of acidic oxygen evolution reaction (OER), Ru sites are prone to undesired overoxidation, leading to substantial deterioration in catalytic activity. Herein, we demonstrate a hydrogen-bond-mediated mechanism triggered by fluoride ion (F^-) in RuO₂ (RuO_1.86F_0.14) to achieve both high activity and stability. The spontaneous transfer of protons to bridging oxygen through hydrogen bonds accelerates the deprotonation of an oxo-intermediate, which improves the kinetics of the OER in acidic conditions. Moreover, the highly electronegative F^- diminishes the covalency of Ru-O bonds and thus boosts the stability of RuO₂. The optimized RuO_1.86F_0.14 catalyst presents an ultralow overpotential of 153 mV at 10 mA cm^-2 and can sustain for more than 980 h with a low degradation rate of 27 μV h^-1. Notably, the RuO_1.86F_0.14 applied in PEMWEs requires only 1.63 V and maintains stable operation for over 100 h at 1 A cm^-2. This work demonstrates a promising anion-modulated approach to the design of high-performance acidic OER catalysts.