Well-organized metal-free chemically reduced graphene oxide sheets as electrocatalysts for enhanced oxygen reduction reactions in alkaline media

Abstract

Metal-free reduced graphene oxides have recently received attention as potential replacements for platinum-based electrocatalysts. In the present study, we investigated the electrochemical characteristics of chemically reduced graphene oxides (C-rGO) in oxygen reduction reactions (ORR). The C-rGO displays significantly enhanced catalytic activity towards the ORR in alkaline solutions compared to the starting graphene oxide (GO). The thermal properties of C-rGO show good thermal stability, and structural defects in C-rGO were confirmed by Raman analysis. Electrochemical impedance spectroscopy (ESI) analysis confirmed C-rGO superior electron transport capacity over GO. The onset potential (0.82 V), lower Tafel slope, and current density (-5.6 × 10-4 mA/cm2) of the C-rGO catalysts were increased compared to GO due to the majority of functional groups removed after chemical reductions. It's clear that catalysts work through four electron (e-) ORR processes bacause the C-rGO has higher electron transfer numbers (3.8 at a potential of −0.63 V).