Highly active ruthenium sites stabilized by modulating electron-feeding for sustainable acidic oxygen-evolution electrocatalysis

Abstract

Designing acid-stable oxygen evolution reaction (OER) electrocatalysts with low noble-metal content to facilitate the sluggish kinetics is crucial for sustaining green hydrogen generation. Herein, we developed a rutile-structured ruthenium–manganese solid solution oxide with oxygen vacancies (Mn_0.73Ru_0.27O_2−δ) by using an electron-feeding modulation strategy to stabilize the catalyst structure and accelerate the OER kinetics. Due to the optimal electronic structure and enhanced electrical conductivity, the Mn_0.73Ru_0.27O_2−δ catalyst displayed a low overpotential of 208 mV to reach 10 mA cm⁻² current density in 0.5 M H₂SO₄ electrolyte, outperforming the benchmark RuO₂ and most previously reported noble-metal based OER catalysts. Experimental characterization verified that the electron transfer occurred from Ru to Mn atoms with the bridging O atom, which was further enhanced with the existence of oxygen vacancies. Therefore, the center Ru active sites in an electron-deficient state is favorable for bonding with active oxygen intermediates. Meanwhile, theoretical calculations revealed that the simultaneous incorporation of Mn components and O vacancies significantly decreased the anti-bonding spin states of Ru's d-orbitals, which modulated the adsorption and desorption energy barriers of elementary reactions on the active Ru sites, thus boosting the overall OER kinetics.