Bifunctional platinum group metal-free iron–manganese catalyst for long-term rechargeable zinc-air batteries

Rechargeable zinc-air batteries (ZABs) are promising for sustainable energy storage; however, their widespread application is limited by the high cost and scarcity of platinum group metal (PGM) catalysts. This study presents a novel platinum group metals-and cobalt-free bimetallic Fe/Mn catalyst, synthesized via a sol–gel method with urea and surfactants, followed by low-temperature thermal treatments. Two thermal routes were investigated: one in air and another in ammonia flow. Characterization by SEM, BET, TGA-DTA, FTIR, Raman, and XRD revealed distinct structural differences. The ammonia-treated catalyst showed a high surface area (182 m 2 /g) and incorporation of nitrogen and carbon into the structure, forming nitrides and graphitic carbon, which contributed to enhanced porosity and catalytic performance. Electrochemical tests confirmed bifunctional activity for both the oxygen reduction (ORR) and oxygen evolution (OER) reactions. Notably, the NH 3 -treated catalyst demonstrated superior long-term stability during galvanostatic cycling in a ZAB setup. These findings highlight the potential of Fe/Mn-based, PGM-free catalysts for the development of long-life