Synergistically enhancing oxygen electrocatalysis through the robust interaction interface between the Fe single-atom substrate and M@NC nanoparticles

Abstract

The dissolution and detachment of the metal active sites in harsh environments are critical challenge limiting the application of supported metal catalysts in Zn-air batteries (ZABs). Herein, we report an in-situ reduction strategy to synthesize transition metal nanocrystals encapsulated in graphitic carbon shells, stably anchored on a silk-derived Fe, N co-doped carbon substrate (Fe-Silk/FeNi₃@NC). The core-shell structure along with the strong interactions between the carbon substrate and metal effectively prevents corrosion and loss of the metal active sites during operation, leading to exceptional cycling stability in both liquid and solid ZABs. In situ X-ray absorption fine structure spectroscopy reveals changes in the electronic structure during catalysis. Additionally, in situ Raman spectroscopy confirms that these changes are attributable to the adsorption of oxygen-containing intermediates on the active sites. Furthermore, density functional theory calculations confirm the viability of coupling the two catalytic sites to achieve bifunctional catalytic activity via this in situ reduction strategy. The robust interaction interface formed by the coupling of these catalytic sites optimizes the reaction energy barriers and enhances the stability of the electrocatalyst. This work provides a solution to the instability of supported metal catalysts and introduces a novel approach for the sustainable use of low-cost biomass waste materials.