Tuning oxygen vacancy via transition metal doping for efficient oxygen evolution reaction

In this paper, a series of Cr-doped RuO₂@NC catalysts (Cr_0.1-RuO₂@NC, Cr_0.2-RuO₂@NC, Cr_0.4-RuO₂@NC) with controlled Cr doping (0.5%, 1%, 3%) were prepared to investigate the mechanistic interplay between transition metal doping, oxygen vacancy (O_V) formation and oxygen evolution reaction (OER) performance. Systematic characterization results reveal that the oxygen vacancy concentration follows a volcano-type trend with increasing Cr content, peaking at 1% Cr doping (Cr_0.2-RuO₂@NC). Combined X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses confirm that Cr doping effectively induces electronic structure reconstruction of RuO₂, generating high-density oxygen vacancies that serve as electrochemically active sites. The optimized Cr_0.2-RuO₂@NC catalyst exhibits exceptional OER performance, achieving a low overpotential of 223 mV at 10 mA/cm² and a Tafel slope of 63.8 mV/dec, significantly surpassing its 0.5% and 3% doped counterparts. Remarkably, it retains 99.9% of the initial activity after 27 h. Cr doping not only regulates the concentration of oxygen vacancies through lattice distortion. The strong Cr–O covalent bonding enhances the structural stability of the catalyst. This work establishes a general transition metal doping strategy for precise oxygen vacancy engineering, providing new design principles and theoretical foundations for developing high-performance OER electrocatalysts.