(Fe₄N/GaN)@GC: A Bifunctional Electrocatalyst for High-Performance Rechargeable Zinc-Air Batteries

Rechargeable zinc-air batteries (ZABs), though offering a high theoretical energy density (1086 Wh kg^-1) and intrinsic nonflammability, require efficient electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). At present, state-of-the-art electrocatalysts for ORR and OER are dominated by noble metals, yet a single catalyst cannot deliver excellent activity for both reactions simultaneously due to distinct reaction kinetics. Herein, we report that a graphitized-carbon-encapsulated Fe₄N/GaN heterostructure formulated as (Fe₄N/GaN)@GC-0.75 (FeGa/C-0.75) delivers high-performance ORR (half-wave potential of 0.857 V) and OER (overpotential of 314 mV at 10 mA cm^-2) electrocatalytic activities. Such a superior performance originates from the unprecedented Fe₄N/GaN heterostructure, in which the adsorption of oxygenated intermediates can be optimized through interfacial electronic coupling of both nitrides. Meanwhile, the graphitic carbon shell protects the heterointerface against corrosion and decay. Therefore, ZABs assembled with FeGa/C-0.75 show a high peak power density of 221 mW cm^-2 with a specific capacity of 726.15 mAh g_Zn ^-1 and maintain stable cycling for over 850 h at 30 mA cm^-2. Moreover, a flexible all-solid-state ZAB enabled by FeGa/C-0.75 can be fabricated with robust performance upon bending. These performances shed light on the broader application of this catalyst for various rechargeable ZABs and flexible devices.