Enhanced oxygen reduction of porous N-doped carbon nanosheets with graphitic N and defects obtained from coal-based graphene quantum dots

Metal-free carbon-based electrocatalysts for oxygen reduction reaction (ORR) have received considerable attention owing to their abundance and low cost. However, designing carbon-based electrocatalysts with excellent performance in a facile manner remains a challenge. In this work, porous nitrogen-doped carbon nanosheet (PNCNs) catalysts with high contents of graphitic N and defects were readily prepared via a simple self-doping method, in which coal-based graphene quantum dots (GQDs) were used as the carbon and nitrogen resource. Based on the results, PNCNs-900 (obtained at 900 °C) displayed good ORR performance, with a half-wave potential ( E 1/2 ) of 0.80 V. It also exhibited high stability and methanol tolerance compared with commercial Pt/C. Experimental investigations and theoretical calculations prove that the increased ORR electrocatalytic activity of PNCNs-900 is due to the synergistic effect of a large number of defects and graphitic N. Furthermore, its higher electrocatalytic activity for ORR also benefits from the porous lamellar structure , which facilitates the mass transfer process. This study offers a novel approach for developing effective ORR catalysts and for the high value-added utilization of coal resources.