Synergistically Efficient Ni/Nb Dual Single-Atomic Sites on N-Doped Carbon for Highly Efficient and Durable Oxygen Electrocatalysis

With flexible charge modulation and high atom utilization, dual-atom catalysts (DSACs) have shown promise in various electrocatalytic reactions for energy conversion applications. Herein, we synthesize an asymmetrical Ni/Nb dual single-atom anchored on the porous N-doped carbon framework (Ni/Nb DSA@NC) through a pyrolysis process. The obtained Ni/Nb DSA@NC dimer delivers an efficient bifunctional electrocatalytic performance in the oxygen reduction reaction (ORR) (E1/2 = 0.952 V) and oxygen evolution reaction (OER) (Ej10 = 1.577 V) in alkaline electrolytes. A series of ex situ and in situ characterizations, combined with the theoretical calculations, suggests that the strong coupling of the adjacent Ni–N4 and Nb–N4 moieties optimized the adsorption–desorption of oxygenated intermediates through adjusting the d-orbital energy level of the Ni atoms, thereby boosting the reaction kinetics of the oxygen electrocatalysis. Interestingly, the more unoccupied orbitals and fewer d electrons of the Nb atom could strengthen the Ni–N bonding and suppress Ni demetalation, guaranteeing impressive durability. Notably, the Ni/Nb DSA@NC-based zinc–air battery (ZABs) and hydroxide exchange membrane fuel cell (HEMFC) provide attractive maximum power densities of 362.1 mW cm–2 and 1.26 W cm–2, respectively. This research offers valuable insight for designing Ni-based DSAs bifunctional oxygen electrocatalysts for the energy conversion process.