  We report on the development of two new Pt-free electrocatalysts (ECs) for
the oxygen reduction reaction (ORR) based on graphene nanoplatelets (GNPs). We
designed the ECs with a core-shell morphology, where a GNP core support is
covered by a carbon nitride (CN) shell. The proposed ECs present ORR active
sites that are not associated to nanoparticles of metal/alloy/oxide, but are
instead based on Fe and Sn sub-nanometric clusters bound in coordination nests
formed by carbon and nitrogen ligands of the CN shell. The performance and
reaction mechanism of the ECs in the ORR are evaluated in an alkaline medium by
cyclic voltammetry with the thin-film rotating ring-disk approach and confirmed
by measurements on gas-diffusion electrodes. The proposed GNP-supported ECs
present an ORR overpotential of only ca. 70 mV higher with respect to a
conventional Pt/C reference EC including a XC-72R carbon black support. These
results make the reported ECs very promising for application in anion-exchange
membrane fuel cells. Moreover, our methodology provides an example of a general
synthesis protocol for the development of new Pt-free ECs for the ORR having
ample room for further performance improvement beyond the state of the art.
