Modulating electronic structure of interfacial Fe sites in Fe2N/CoFe2O4 nano-heterostructure for enhancing corrosion-resistance and oxygen electrocatalysis in zinc-air battery

Interface engineering can regulate electronic structure of transition-metal nitrides to promote their electrocatalytic activities. However, design of iron nitride (Fe2N)-based electrocatalytic interface with desirable properties is still challenging. Here, an in-situ nucleation strategy is developed to construct the highly-dispersed Fe2N/spinal (CoFe2O4) heterojunctions to optimize the electro-conductivity and activity. The heterostructure exhibits robust activities towards ORR (half-wave potential, 0.903 V) and OER (overpotential, 300 mV). Interfacial interactions between Fe2N and CoFe2O4 mitigate the corrosion (leaching) and severe agglomeration of active components in harsh environments to stabilize the electrocatalytic activity, maintaining the integrity of heterostructure and the sustainable exposure of active sites. Theorical calculations confirm the feasibility of incorporating Fe2N into basal plane of spinal lattice (Fe2N (0 0 2) and CoFe2O4 (4 0 0) is well matched). Modulated electronic state optimizes the adsorption/desorption strength of O-intermediates on the interfacial Fe-sites (the main active sites) of Fe2N/CoFe2O4 for both ORR and OER. Strong coupling of Fe2N and CoFe2O4 bolsters the charge-transfer across the interfaces to substantially accelerate the ORR/OER kinetics. Notably, by vital of a small potential-gap (0.634 V), it displays excellent power-density (225 mW cm−2) and cycling-stability (280 h) in zinc-air battery. This work enriches the understanding of electronic structure modulation of hetero-structured nitride/spinel-based electrocatalysts.