Surface functionalization of acidified graphene through amidation for enhanced oxygen reduction reaction

Abstract

Introducing nitrogen atoms is an effective approach to generate graphene-based electrode materials for energy conversion-electrochemical devices. Herein we propose a novel strategy to covalently functionalize the surface of graphene using 4-amino-4H-1,2,4-triazole (AT) and acidified graphene oxide (AGO) to convert the epoxy group to a carboxyl group in the latter to increase the number of amidation sites via a wet chemical method. It has been proven that, compared to graphene oxide (GO), AGO can be covalently functionalized with AT more efficiently due to the selective amidation between the carboxyl and amine groups. Covalent functionalization incorporates nitrogen and creates pores, which increase the number of oxygen reduction reaction (ORR) sites and prevents π-π stacking of graphene sheets. The prepared catalyst exhibits superior ORR activity, in terms of current density, electron transfer and stability compared to Pt/C. It has found that the superior ORR performance of the prepared catalyst is due to the higher degree of amidation that leads to the creation of abundant ORR active N-sites at nanoscale level and a porous structure at microscale level, which enhances O2 mass transportation to the active sites and improve tolerance against methanol during ORR.