Robust Electronic Structure: Uncovering the Origins of Fast Oxygen Reduction Kinetics of the NiCo Nanoalloys@N-Doped Carbon

Thenon-noble nanoalloy family is one of the promising catalystsfor oxygen reduction reactions and zinc-air batteries. However,the complex reconstruction behavior is not clear enough for guidingthe design of alloy catalysts. The origins of reaction kinetics duringdrastic aging require further investigation. Hence, we prepare severalNiCo nanoalloys@NC with tunable electronic structures. Among them,Ni2Co4@NC displays a suitable electronic structure,in which the interacted Ni and Co sites accelerate oxygen reductionand evolution reactions. It delivers an ultralow Tafel slope of 46.3mV dec(-1) for the oxygen reduction reaction and 65.0mV dec(-1) for the oxygen evolution reaction and releasesan excellent power density of 162.9 mW cm(-2) in thezinc-air battery. With ex situ Raman and other characterizations,we subsequently deduce the reconstruction behavior of these NiCo nanoalloys@NCsamples. The suitable surface oxyhydroxide-hydroxide-oxideshell accounts for the excellent stability and reaction kinetics ofNi(2)Co(4)@NC. With density functional theory simulations,we further discover its robust electronic structure during the drasticreconstruction so that it displays rapid kinetics after aging. Inthe experiment, its oxygen reduction reaction (ORR) Tafel slope merelyincreased from 46.3 to 48.6 mV dec(-1). We highlightthe decisive role of the surface electronic structure in electrochemicalkinetics and explain how to achieve excellent stability.

Automated summary

Researchers prepared NiCo nanoalloy@NC samples with tunable electronic structures, among which Ni2Co4@NC showed a suitable electronic structure for promoting oxygen reduction and evolution reactions, demonstrating excellent stability and reaction kinetics. Through experiments and theoretical simulations, the reconstruction behavior of these nanoalloys@NC samples and their crucial role in electrochemical kinetics were revealed.