Integrating Fe-N coordination with durable Fe-F species towards efficient oxygen reduction in anion exchange membrane fuel cells

Phen strongly coordinates dissociative Fe ions to form active Fe-N X sites. • The strong coupling of Fe-F strengthens the poisoning resistance of the catalyst. • N,F co-doped network enhances ORR by lowering reaction energy barrier at Fe-N X sites. • Porous chain-bead framework prevents agglomeration, providing abundant sites and fast charge transfer. • AEMFCs with FeN X @Fe-F-CNF cathodes achieve a peak power density of 0.7 W cm −2 . Transition-metal-nitrogen-carbon (M-N-C) catalysts have garnered significant recognition as highly active non-precious metal catalysts for the oxygen reduction reaction (ORR) in anion exchange membrane fuel cells (AEMFCs), attributable to their low-cost, high atom-utilization and remarkable ORR performance. However, the primary drawback of conventional M-N-C catalysts lies in the suboptimal electronic structure of their metal centers (M-N 4 ), which results in excessively strong adsorption energy toward oxygen intermediates, thereby limiting their intrinsic activity and stability. Herein, the FeF 2 /Fe 3 N nanocrystalline decorated N, F co-doped chain-bead Fe-N-C fiber network (FeN X @Fe-F-CNF) has been fabricated by electrospinning strategy through utilizing 1,10-Phenanthroline monohydrochloride monohydrate (Phen) and NH 4 F as nitrogen/fluoride sources respectively. The six-membered heterocyclic in Phen allows for strong coordination with dissociative Fe ions, thus, promoting the formation of Fe-N X sites. Furthermore, co-doped N, F is able to tune the electronic structure of Fe active sites, whereas flexible chain-bead nanofibers guarantee considerable structural adaptation, thereby contributing to the enhancement of their catalytic activity and stability. The obtained FeN X @Fe-F-CNF exhibits enhanced ORR catalytic activity (with an E 1/2 of 0.863 V) and superior durability (with a current retention of 90.7 % after maintaining the ORR typical potential range for 100,000 seconds and a E 1/2 negative shift of 7 mV after 5000 continuous potential cycles). Furthermore, the assembled AEMFCs based on FeN X @Fe-F-CNF catalysts demonstrate excellent performance, with a peak power density of 0.7 W cm −2 , indicating its potential feasibility for commercial applications. Download: Download high-res image (293KB) Download: Download full-size image