Regulating Ru–Ru Distance in RuO₂ Catalyst by Lattice Hydroxyl for Efficient Water Oxidation

Highly active and durable electrocatalysts for the oxygen evolution reaction (OER) are crucial for proton exchange membrane water electrolysis (PEMWE). While doped RuO₂ catalysts demonstrate good activity and stability, the presence of dopants limits the number of exposed active sites and complicates Ru recovery. Here, we present a monometallic RuO₂ (d-RuO₂) with lattice hydroxyl in the periodic structure as a high-performance OER electrocatalyst. The obtained d-RuO₂ catalyst exhibits a low overpotential of 150 mV and long-term operational stability of 500 h at 10 mA cm^-2, outperforming many Ru/Ir-based oxides ever reported. A PEMWE device using d-RuO₂ sustains operation for 348 h at 200 mA cm^-2. In-situ characterization reveals that the incorporation of lattice hydroxyl increases the Ru-Ru distance, which facilitates the turnover of the Ru oxidation state and promotes the formation of stable edge-sharing [RuO₆] octahedra during the OER, thereby accelerating the formation of O-O bonds and suppressing the overoxidation of Ru sites. Additionally, the small particle size of the catalyst decreases the three-phase contact line and promotes bubble release. This study will provide insights into the design and optimization of catalysts for various electrochemical reactions.