High-Performance Iron-Based ORR Catalysts Synthesized via Chemical Vapor Deposition

A Fe-N-C catalyst was synthesized via chemical vapor deposition (CVD) of gas phase FeCl3 onto a metal organic framework (MOF)-derived N-doped carbon (N-C) substrate at 750 ℃. This catalyst exhibits an unprecedented current density of 0.033 mA·cm-2 at 0.90 ViR-free (IR-corrected) and 0.044 mA·cm-2 at 0.89 ViR-free in a H2-O2 proton exchange membrane fuel cell under 1.0 bar and 80 ℃ conditions. The exceptional ORR activity of this catalyst is attributed to the ultra-high density of the Fe(II)-N4 sites. The high density of Fe(II)-N4 sites is realized by CVD that allows for the ready formation of Fe(II)-N4 sites via direct incorporation of gas phase FeCl3 into microporous N-C defects at relatively low temperatures. At these low temperatures, the doped N and Fe(II)-N4 are better preserved as compared to those in previous Fe-N-C catalysts synthesized via pyrolysis of the mixture of Fe, N, and C precursors at 1000 ± 100 ℃.