Ultrafast Activity Tuning and Kilogram-Scale Synthesis of Fe-N-C Catalysts via Confinement-Engineered Joule Heating.

Atomically dispersed Fe-N-C catalysts with well-defined iron-nitrogen coordination exhibit fantastic promise for the oxygen reduction reaction (ORR). However, achieving their scalable synthesis while preventing iron aggregation and performance degradation remains a critical challenge. Here, we demonstrate a highly efficient confined flash Joule heating (CFJH) technique for the scalable and ultrafast synthesis of Fe-N-C catalysts. The coal-derived porous carbons are efficient in confining iron phthalocyanine (FePc) molecules, suppressing their migration and iron aggregation during ultrafast CFJH treatment. This process facilitates the conversion of FePc into atomically dispersed FeN4 sites embedded within a graphitization-enhanced carbon framework. Mechanistic studies reveal that, compared to an FePc precursor, these integrated FeN4 sites exhibit a shifted rate-determining step with optimized adsorption/desorption of oxygen intermediates, leading to a reduced energy barrier for efficient 4e- oxygen reduction. The resulting catalyst exhibits impressive ORR activity in alkaline media with a high half-wave potential (0.90 V vs RHE) and remarkable durability (94.5% retention over 100 h). The assembled zinc-air battery delivers a peak power density of 277.6 mW cm-2 and sustains stable operation for over 900 h, outperforming the Pt/C + IrO2 benchmark. Scalable production is achieved at a rate of 0.5 kg h-1, establishing a facile and industrially viable route for synthesizing high-performance atomically dispersed catalysts.