Fluorine-decorated high loading Fe-N-C electrocatalysts for proton exchange membrane fuel cells

Fe-N-C electrocatalysts bear the high promise to eventually substitute platinum for acidic oxygen reduction reaction (ORR). However, the loading of atomically dispersed Fe in Fe-N-C is frequently less than 3 wt% and has a relatively low ORR activity. Herein, we report the synthesis of F-decorated Fe-N-C (F-Fe-N-C) by pyrolysis of trifluoromethyl imidazole decorated zeolitic imidazolate framework-8 with hemin as Fe precursor. Interestingly, F-Fe-N-C exhibits an exceptional half-wave potential of 0.858 V ( vs. RHE) primarily because of atomically dispersed 7.1 wt% Fe in the form of Fe III N 4 C 12 and Fe II N 4 C 10 . Moreover, F-Fe-N-C catalyst layers (CLs) enable a high single cell power density that is 2.4 times that of house-made Fe-N-C. According to theoretical studies together with mercury intrusion porosimetry, the enhancement of single cell performance appears to originate from the high activity of F-Fe-N-C, abundant pore volume including nanopores where Knudsen diffusion dominates, and F-induced scattered distribution of ionomer for proton transfer. Fluorine-decorated Fe-N-C achieves 7.1 wt% of atomically dispersed Fe loading. F promotes nanopore creation and ionomer distribution in the catalyst layer, suitable for O 2 and proton transfer.