Abstract
A nitrogen-containing covalent organic framework obtained from the polymerization of 1,3-dicyanobenzene has been used as a starting material for the synthesis of Fe/N/C catalysts for the oxygen reduction reaction (ORR). In this work we report the effect of the thermal treatments on the nature and catalytic properties of the catalysts obtained after the thermal treatments. After the first thermal treatment, the catalysts obtained contain metallic iron and iron carbide particles, along with a minority fraction of inorganic FeN
sites. After acid leaching and a second thermal treatment, FeN
sites remain in the catalysts, along with a minor fraction of graphite-wrapped Fe
C particles. Both catalysts display high activity for the ORR, with the catalyst subjected to acid leaching and a second thermal treatment, 2HT-1,3DCB, displaying higher ORR activity and a lower production of H
O
. This observation suggests that iron particles, such as Fe
C, display ORR activity but mainly toward the two-electron pathway. On the contrary, FeN
ensembles promote the ORR via the four-electron pathway, that is, via H
O formation.