Revealing the Synergistic Enhancement Effect of Dual Metal RuFe(Co) Sites for Bifunctional Oxygen Catalysis

Modifying the geometric and electronic structures of metal–N–C single-atom catalysts to improve their catalytic activities is quite desirable and challenging. Here, theoretical analysis and experiment indicate the inherent synergistic effect of dual metal sites in N-doped carbon for bifunctional ORR and OER. Specifically, introducing Ru to generate RuFe–N–C or RuCo–N–C double-atom catalysts (DACs) can significantly enhance the bifunctional ORR/OER activities of Fe(Co) and Ru sites, exceeding the equivalent single metal Fe(Co)–N–C and Ru–N–C. Investigations of a series of RuM–N–C DACs reveal that the intriguing synergistic effect results from the modified charge density and d-band center by combining two optimized metal atoms, which affects adsorption energies of intermediates and catalytic activity. Based on these theoretical guidelines, RuFe–N–C is synthesized using a bimetal MOF as the precursor, and it exhibits exceptional ORR/OER activities in alkaline media with a small ΔE of 0.63 V, significantly outperforming Fe–N–C, Ru–N–C, and even commercial Pt/C-RuO2.