N,P-Coordinated Breaking Local Charge Symmetry of Fe Single Atoms for Highly Efficient Electrocatalytic Oxygen Reduction

Efficient and durable electrocatalysts for the oxygen reduction reaction (ORR) are pivotal in energy conversion and storage systems, particularly in alkaline fuel cells and metal-air batteries. Atomically dispersed Fe-NC electrocatalysts are a promising alternative to platinum group metal (PGM) catalysts. However, their catalytic activity and stability must be significantly improved. In this study, we introduce P atoms to disrupt the local charge symmetry of the Fe-N₄ configuration, thereby reducing the ORR energy barrier and boosting the electrocatalytic performance. The resulting atomically dispersed Fe catalyst (FeN₃PO) exhibits exceptional ORR activity under alkaline conditions, achieving a half-wave potential of 0.91 V, which is 57 mV higher than that of the Pt/C catalyst. Furthermore, it demonstrated negligible performance degradation during stability testing. When employed as the cathode catalyst in rechargeable zinc-air batteries, FeN₃PO delivers a power density that far exceeds that of the 20% Pt/C catalyst, reaching 257 mW cm^-2. Density functional theory calculations reveal that doping with P optimizes the Fe 3d orbitals and accelerates the rate-determining step, thereby significantly enhancing the catalytic activity. This research provides novel insights into the optimization of non-precious metal single-atom ORR catalysts.