Controllable Solid-Phase Fabrication of an Fe₂O₃/Fe₅C₂/Fe–N–C\nElectrocatalyst toward Optimizing the Oxygen Reduction Reaction in\nZinc–Air Batteries

Abstract

Preparing advanced electrocatalysts\nvia solid-phase reactions encounters\nthe challenge of low controllability for multiconstituent hybridization\nand microstructure modulation. Herein, a hydrothermal-mimicking solid-phase\nsystem is established to fabricate novel Fe₂O₃/Fe₅C₂/Fe–N–C composites consisting\nof Fe₂O₃/Fe₅C₂ nanoparticles\nand Fe,N-doped carbon species with varying morphologies. The evolution\nmechanism featuring a competitive growth of different carbon sources\nin a closed hypoxic space is elucidated for a series of Fe₂O₃/Fe₅C₂/Fe–N–C composites.\nThe size and dispersity of Fe₂O₃/Fe₅C₂ nanoparticles, the graphitization degree of the carbonaceous\nmatrix, and their diverse hybridization states lead to disparate electrocatalytic\nbehaviors for the oxygen reduction reaction (ORR). Among them, microspherical\nFe₂O₃/Fe₅C₂/Fe–N–C-3\nexhibits an optimal ORR performance and the as-assembled zinc–air\nbattery shows all-round superiority to the Pt/C counterpart. This\nwork presents a mild solid-phase fabrication technique for obtaining\na variety of nanocomposites with effective control over composition\nhybridization and microstructural modulation, which is significantly\nimportant for the design and optimization of advanced electrocatalysts.