Oxygen vacancy shortened oxophilic Mo-lattice Ru dual sites in ruthenium oxide with accelerated oxygen–oxygen radical coupling for efficient acidic oxygen evolution reaction

Abstract

Activating and manipulating the reaction pathway at active sites is essential for the design of Ru-based electrocatalysts. Herein, oxophilic Mo atoms were atomically dispersed in the oxygen-vacancy-enriched RuO ₂ lattices (Mo–RuO _2-x ) through molten salt treatment, in which oxygen-vacancy-shortened Ru–Mo dual sites are constructed and responsible for the improved acidic oxygen evolution reaction (OER). The Mo–RuO _2–x electrocatalyst exhibits a low overpotential of 191 mV at 10 mA cm ⁻² for acidic OER and maintains sustained operation exceeding 500 h. More excitingly, the proton exchange membrane water electrolyzer (PEMWE) assembled with Mo–RuO _2-x as the anode could survive from a 500 h operation at 1 A cm ⁻² , with a cell voltage of 1.63 V. Experimental characterizations and theoretical calculations together evidence that the oxygen-vacancy-shortened Ru–Mo dual sites efficiently activate the oxide path mechanism (OPM), with oxophilic Mo possessing a higher d-band center than Ru, which favors the adsorption of O* intermediates and accelerates the *OO* coupling process for the improved acidic OER performance. This work demonstrates an alternative approach for the regulation of OPM at dual sites via lattice and oxophilicity engineering, which is guiding the design of Ru-based electrocatalysts toward industrial-level PEMWE.