Graphene-covered FePc as a model of the encapsulated type of catalyst for the oxygen reduction reaction

Abstract

Carbon atomic layers with encapsulated transition metal nanoparticles exhibit high catalytic activity for the oxygen reduction reaction (ORR), and good tolerance for poisoning species and acid leaching. However, the active sites and catalytic mechanism are not yet clear, mainly due to the highly heterogeneous structure of encapsulated types of catalysts. In this study, we developed a new model catalyst to mimic encapsulated types of catalysts by covering the well-defined active sites of iron phthalocyanine (FePc) with a monolayer of graphene. It was found that the FePc can activate the surface carbon layer to catalyze the ORR. Unlike exposed FePc on graphene, the embedded catalyst is insensitive to poisoning by SCN− ions. The designed model catalyst demonstrates that molecular type active sites, as well as metal nanoparticles, can form encapsulated catalysts for ORR. The simple and well-defined structure of this model catalyst is helpful for investigating the active sites and the catalytic mechanism at the atomic scale.