Pre-doped oxygenated defects activate nitrogen-doped graphene for the oxygen reduction reaction

Abstract

The presence of defects and chemical dopants in metal-free carbon materials plays important roles in the electrocatalysis of the oxygen reduction reaction (ORR). The precise control and design of defects and dopants in carbon electrodes will allow the fundamental understanding of activity-structure correlations for tailoring catalytic performance of carbon-based, most particularly graphene-based electrode materials. Herein, we adopted monolayer graphene – a model carbon-based electrode – for systematical introduction of nitrogen and oxygen dopants, together with vacancy defects, and studied their roles in catalyzing ORR. Compared to pristine graphene, nitrogen doping exhibited a limited effect on ORR activity. In contrast, nitrogen doping in graphene pre-doped with vacancy defects or oxygen enhanced the activities by 3.7 and 6.8 times, respectively. The optimal activity was achieved for nitrogen doping in graphene functionalized with oxygenated defects – 4.6 times more than nitrogen-doped and 7.3 times more than pristine graphene. More importantly, oxygenated defects is highly related to the 4e− pathway instead of nitrogen dopants. This work indicates a non-negligible contribution of oxygen and especially oxygenated vacancy defects for the catalytic activity of nitrogen doped graphene.