Towards 'Pt-free' Anion-Exchange Membrane Fuel Cells: Fe-Sn Carbon Nitride-Graphene 'Core-Shell' Electrocatalysts for the Oxygen Reduction Reaction

TL;DR

This paper introduces novel Pt-free Fe-Sn carbon nitride-graphene core-shell electrocatalysts for oxygen reduction, showing promising performance close to platinum-based catalysts and offering a scalable synthesis method for fuel cell applications.

Contribution

Developed new Fe-Sn based core-shell electrocatalysts with a graphene core and carbon nitride shell for ORR, demonstrating high activity without platinum.

Findings

ORR overpotential only ~70 mV higher than Pt/C

Electrocatalysts show promising activity in alkaline medium

Methodology allows scalable synthesis of Pt-free catalysts

Abstract

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.