Chemical vapor deposition towards atomically dispersed iron catalysts for efficient oxygen reduction

Abstract

Fe–N–C single-atom catalysts (SACs) are regarded as promising alternatives to commercial Pt/C for the oxygen reduction reaction (ORR). Directly converting the easily available bulk iron precursors into atomically dispersed Fe active centers is an efficient route but still faces challenges. Herein, a capable one-pot chemical vapor deposition strategy (CVD) is described to fabricate N-coordinated Fe single-atom (Fe-SA/NC) catalysts for high-performance ORR. Briefly, ferrocene(II) powder underwent sublimation into flowing vapor sources and was subsequently trapped by highly porous nitrogen-rich zeolitic imidazolate frameworks (ZIFs) support and chemically transformed to isolated Fe–N sites by subsequent pyrolysis. Both spectroscopic and microscopic characterizations revealed the atomic dispersion of Fe species coordinated by four nitrogen atoms. Thus, Fe-SA/NC catalysts show superior alkaline ORR performance with a half-wave potential of 0.902 V versus RHE and a 2.01 larger turnover frequency value than that of counterparts. When assembled into Zn–air batteries as the air electrode, the Fe-SA/NC catalysts exhibited a large peak power density of 215 mW cm⁻² at 340 mA cm⁻² current and maintained low voltage fluctuation after 4000 cycles of service. This work highlights the simplicity of the one-pot CVD strategy toward fabricating Fe–N–C single-atom catalysts for highly effective ORR.