Boron Vacancy Enhanced Ru─Mo Electron Bridge as an Efficient Electrocatalyst for Anion Exchange Membrane Electrolysis

Hybrid electrocatalysts combining noble metals with tailored supports are crucial for efficient hydrogen evolution reaction (HER) across a wide pH range. Here, we report a ruthenium cluster catalyst anchored on molybdenum boride support engineered with boron vacancies (Ru/MoB-B_V) for highly efficient HER. The introduced boron vacancies optimize the electronic interactions between molybdenum boride and the Ru cluster via a Ru─Mo electron bridge, leading to enhanced catalytic performance and stability. Combined electrochemical analysis and density functional theory calculations reveal that Ru/MoB-B_V possesses a favorable water-dissociation energy and optimal desorption energies for hydrogen/hydroxide intermediates on Ru clusters. These merits confer exceptional HER performance, with overpotentials of 40 and 34 mV at 10 mA cm^-2 in alkaline freshwater and seawater, respectively; 24 mV in acidic electrolyte; and 67 mV in neutral electrolyte. Importantly, the activated Ru and Mo sites enable an anion exchange membrane electrolyzer employing Ru/MoB-B_V as the cathode to exhibit remarkable stability, operating for 100 h at 500 mA cm^-2. This work provides insights into the design of highly efficient and stable catalysts through the precise engineering of surface vacancies.