Competitive Adsorption Mechanism of Defect-Induced d-Orbital Single Electrons in SrRuO₃ for Alkaline Hydrogen Evolution Reaction

In the alkaline hydrogen evolution reaction (HER), the dissociation energy barrier of water, and the easy adsorption of OH on the catalyst are key factors that limit the catalytic activity. This work proposes a novel competing adsorption mechanism driven by d_z² electrons in the context of the alkaline HER. The high concentration of oxygen vacancies in Co doped SrRuO₃ (V-SRCO) results in the electron filling in the Ru 4d_z² orbital. Under alkaline conditions, the V-SRCO exhibits a low overpotential of only 57.8 mV with a Tafel slope of 35 mV dec⁻¹. Moreover, it exhibits sustained high activity for 60 h. The high HER activity of V-SRCO can be attributed to the presence of a single electron in the d_z² orbital, which reduces the energy barrier for water dissociation. More importantly, the active electrons in the d_z² orbital can inject into the antibonding orbitals of OH, creating an unfavorable environment for OH adsorption on the catalyst. This work provides favorable conditions for efficient HER.