Robust Spray Combustion Enabling Hierarchical Porous Carbon-Supported FeCoNi Alloy Catalyst for Zn-Air Batteries.

Rechargeable Zn-air batteries (RZABs) are poised for industrial application, yet they require low-cost, high-performance catalysts that efficiently facilitate both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). The pivotal challenge lies in designing multimetal active sites and optimizing the carbon skeleton structure to modulate catalyst activity. In this study, we introduce a novel hierarchical porous carbon-supported FeCoNi bifunctional catalyst, synthesized via a spray combustion method. The carbon, derived from sucrose, was tailored into a hierarchical porous morphology through etching with NO₃^- ions and NaCl, thereby significantly increasing the surface area for the interaction of the O₂ and electrolyte interaction. The in situ formation of FeCoNi alloy nanoparticles ensures their uniform dispersion and anchoring, facilitating electron transport. The strong interaction and charge transfer at the heterogeneous FeCoNi alloy interfaces, along with nitrogen doping, which enhances the OER/ORR activity, endow the FeCoNi/N-PC catalyst with exceptional bifunctional catalytic properties, characterized by an activity parameter of 0.73 V. Furthermore, the RZAB assembled with this catalyst demonstrates outstanding cycling stability and reversibility, with a minimal round-trip efficiency decay of 7.6% over 1380 cycles (460 h) at 10 mA cm^-2.