Mo₂B₂O₂-supported Cu and Ni heterogeneous dual atom catalysts for oxygen reduction reactions and oxygen evolution reactions

Dual-atom catalysts with heteronuclear active sites (h-DACs) have better potential in oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) than the recognized single atom catalysts (SACs), but the basic understanding of the mechanism is still lacking. Herein, by constructing h-DACs with different distances of Cu and Ni atoms loaded onto MBenes, the metal atoms loading capacity is significantly increased while maintaining the excellent catalytic activity of SACs. The h-DACs possess more flexible active sites compared to SACs. Controlling the distance between the dual atoms is crucial for the catalytic mechanism and activity. The results indicate that the synergistic effect between the dual metal atoms in h-DACs breaks the scaling relationships between the binding energies of the oxygen intermediates, thereby enhancing the ORR and OER catalytic activity of the corresponding SACs. It is worth noting that when the interatomic distance between Cu and Ni atoms is 3.21 Å, ORR is executed through 4e^- *OOH dissociation mechanism and the system exhibits ultra-low ORR and OER overpotentials of 0.16 V and 0.18 V, respectively, far lower than advanced Pt and IrO₂/RuO₂ of 0.45 V and 0.56/0.42 V, making h-DACs a promising ORR/OER bifunctional electrocatalyst. This work not only provides deep insights into the fundamental understanding of reaction mechanism and catalytic activity for h-DACs but also provides guidance for designing efficient catalysts.