Tuning the Site-to-Site Interaction in Ru–M (M = Co, Fe, Ni) Diatomic Electrocatalysts to Climb up the Volcano Plot of Oxygen Electroreduction

The modulating of the geometric and electronic structures of metal–N–C atomic catalysts for improving their performance in catalyzing oxygen reduction reactions (ORRs) is highly desirable yet challenging. We herein report a delicate “encapsulation–substitution” strategy for the synthesis of paired metal sites in N-doped carbon. With the regulation of the d-orbital energy level, a significant increment in oxygen electroreduction activity was demonstrated in Ru–Co diatomic catalyst (DAC) compared with other diatomic (Ru–Fe and Ru–Ni) and single-atomic counterparts. The Ru–Co DAC efficiently reduces oxygen with a halfwave potential of 0.895 V vs RHE and a turnover frequency of 2.424 s–1 at 0.7 V, establishing optimal thermodynamic and kinetic behaviors in the triple-phase reaction under practical conditions. Moreover, the Ru–Co DAC electrode displays bifunctional activity in a gas diffusion Zn–air battery with a small voltage gap of 0.603 V, outperforming the commercial Pt/C|RuO2 catalyst. Our findings provide a clear understanding of site-to-site interaction on ORR and a benchmark evaluation of atomic catalysts with correlations of diatomic structure, energy level, and overall catalytic performance at the subnanometer level.