Job-synergistic engineering from Fe3N/Fe sites and sharp-edge effect of hollow star-shaped nitrogen-doped carbon structure for high-performance zinc-air batteries

Abstract

Due to the limited sources, high cost, and poor long-term stability of noble metal catalysts, the large-scale commercial application of zinc-air batteries has been restricted. Therefore, designing non-noble metal catalysts with excellent activity and stability for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) blossoms in the ascendant. Herein, we report a hollow star-shaped dual-functional electrocatalyst with uniform and dispersed Fe3N/Fe nanoparticles derived from zeolitic imidazolate framework (ZIFs) by a simple sacrificial template strategy. This hollow structure has the characteristics of low density, thin shell, and high permeability, and its internal cavity not only provides additional three-phase interfaces to accelerate O2 reduction and evolution but also promotes the diffusion of reactants onto the catalyst. By controlling the input amount of iron metal salt, the dispersion degree of FeNP can be effectively adjusted, and the generated Fe3N introduces abundant Fe-NX active sites. Density functional theory calculations show that the strong affinity between Fe3N and FeNP is favorable for promoting the oxygen intermediate reaction, achieving a job-synergistic catalytic effect and high reaction kinetics. The synthesized Fe3N/FeNP-N-C-3.3% exhibits excellent dual-functional activity for OER and ORR, with a high half-wave potential of 0.867 V for ORR (better than the commercial Pt/C of 0.82 V) and an overpotential of only 294 mV for OER at 10 mA cm−2. The rechargeable Zn-air battery prepared with Fe3N/FeNP-N-C-3.3% as an air cathode shows a long-term cycling performance of over 750 h and a maximum power density of 205 mW cm−2. The flexible Zn-air battery has a high open-circuit voltage of 1.48 V and a maximum power density of 52.6 mW cm−2, showing glamorous commercial prospects.