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

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.