Durable Zinc-Air Batteries on a NbN-Modified Fe-N-C Catalyst via a Radical-Scavenging Strategy

Metal-nitrogen-carbon (M-N-C) catalysts are promising non-precious metal catalysts for the oxygen reduction reaction (ORR), yet their practical application is hindered by insufficient long-term stability. The limitation primarily stems from the generation of the two-electron byproduct H₂O₂ and the structural degradation of single-atom sites. Herein, we report a radical-scavenging strategy through the incorporation of non-precious niobium nitride nanoparticles into a Fe-N-C matrix (FeNC-NbN), which achieves exceptional ORR performance. The FeNC-NbN catalyst exhibits a high half-wave potential (E_1/2 = 0.94 V_RHE) with negligible degradation. Furthermore, Zn-air batteries equipped with FeNC-NbN demonstrate outstanding performance, delivering a peak power density of 206.4 mW cm^-2 and an ultralong cycling durability of 2400 h, surpassing most previously reported catalysts. Combined in situ Raman spectroscopy, in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy analyses, and theoretical calculations reveal that the integration of NbN enhances ORR activity by increasing the pyrrolic N content within the FeNC framework. Concurrently, the vacant d-orbitals of Nb effectively interact with and scavenge free radicals, thereby protecting the active sites from degradation and ensuring excellent catalytic activity and stability. This work establishes a viable pathway for developing efficient and durable non-precious ORR electrocatalysts.