FeNi alloys embedded in porous carbon shells on a dual substrate as efficient electrocatalysts for zinc–air batteries

Abstract

Transition metal oxygen evolution/reduction reaction (ORR/OER) catalysts applied to Zn–air batteries (ZABs) have been extensively investigated, but the problems of transition metal electrocatalysts being prone to agglomeration and deactivation at high temperatures and the insufficient stability of the existing single carbon-based catalysts still exist. Herein, we present a dual-substrate strategy that confines first FeNi alloys in N-doped porous carbon shells and then embeds them onto dual-substrate nanofibers of Ti₄O₇ and C (FeNi/NC@Ti₄O₇-CNFs) by electrostatic spinning and annealing treatments. The domain-limiting effect provided by the porous carbon shells disperses the alloys and there is a strong synergy between the alloys and the N-doped carbon shells to modify the electronic structure. Additionally, Ti₄O₇ has excellent stability even in strongly alkaline environments. Accordingly, abundant M–N_X active sites are achieved by the triple synergistic effect of Ti₄O₇ and C formed dual-substrate nanofibers, N-doped porous carbon shells, and highly dispersed alloys. The prepared FeNi/NC@Ti₄O₇-CNFs demonstrated a lower ORR and OER potential difference (ΔE = 0.656 V) than Pt/C and RuO₂. The liquid ZAB assembled with this catalyst has a cycle life of more than 320 h. This work provides a valuable strategy for developing highly active catalysts for application in advanced electrochemical energy devices.