Zinc/graphitic carbon nitride co-mediated dual-template synthesis of densely populated Fe–Nx-embedded 2D carbon nanosheets towards oxygen reduction reactions for Zn–air batteries

Abstract

Atomically dispersed Fe–N–C catalysts have been extensively deemed as appealing substitutes for Pt-series catalysts towards oxygen reduction reactions (ORRs). Nevertheless, most reported Fe–N–C materials suffer from inefficient Fe-based nanoparticles and low-density Fe–N_x sites. Herein, a Zn/g-C₃N₄-mediated dual-template strategy was employed to synthesize densely populated atomic Fe–N_x center-embedded N-doped carbon nanosheets (SAs-Fe/N-CNSs) with adjustable porous structures by the simple pyrolysis of D-glucosamine/FeZn/g-C₃N₄ complexes. g-C₃N₄ works as a structure-guiding 2D template and offers abundant coordination-N trapping sites for anchoring Fe atoms, simultaneously. ZnCl₂ serves as a self-sacrificial template creating a hierarchical porous structure by its volatilization as well as hinders the agglomeration of Fe atoms by spatial segregation during pyrolysis. Due to the high-density atomic Fe–N_x moieties, unique 2D structure, hierarchical porosity, and large surface area, the optimal SAs-Fe/N-CNS catalyst exhibits satisfying ORR performance including excellent activity (E_1/2 = 0.91 V) and desirable durability, surpassing the Pt/C catalyst. Additionally, the superb performance of SAs-Fe/N-CNS-based Zn–air batteries with a maximum power density of 157.03 mW cm⁻² verifies their promising application in practical electrochemical systems.