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

Abstract

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) (E_1/2 = 0.952 V) and oxygen evolution reaction (OER) (E_j10 = 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.