Nickel-Iron Interfacial Alloy Nanoparticles Encapsulated By Pyridinic-N Enriched CNT on Carbon Fiber Cloth for Bifunctional Oxygen Catalysts and Biaxially Flexible Zinc-Air Batteries

Low-price, high-performance, and long-term stability electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are highly significant in the application of rechargeable zinc air batteries. In this study, we report a highly reversible bifunctional electrocatalyst for flexible Zn air batteries featuring pyridinic-N exclusively enriched carbon-nanotube-encased nickel-iron (NiFe) interfacial alloy nanoparticles derived from an LDH template on knitted carbon fiber cloth. NiFe nanoparticles are catalytically released from the NiFe-MOF to form CNT tentacles when pyrolyzed in an inert atmosphere. XPS and XAS studies revealed the dominating presence of pyridinic-N, which reduces electron localization around NiFe centers and improves the interaction with oxygenated species. As a result, the NiFe-N-CNT-KCC catalysts exhibited a low operating overpotential (η10) of 173 mV for the OER and a half-wave potential (E1/2) of 0.87 V for the ORR, superior to benchmark electrocatalysts. As an air cathode for zinc-air batteries, the NiFe-N-CNT-KCC-based battery showed excellent electrochemical performance, with an open circuit voltage (OCV) of 1.55 V, high power density (153 mW cm-2), excellent specific capacity of 793.2 mA h g-1, and long-term stability. Most impressively, the solid-state flexible zinc-air battery with the NiFe-N-CNT-KCC cathode showed admirable rate performance and exceptional mechanical stability under arbitrary bending and twisting conditions, holding great potential in practical implementation in next-generation high-power and high-energy-density batteries, even with the potential for wearable applications.