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 got considerable attention due to their abundant reserves and low cost. However, it is of a challenge to reasonably design carbon-based electrocatalysts with an excellent performance in a facile way. In this work, porous nitrogen-doped carbon nanosheet (PNCNs) catalysts with high content of graphitic N and defects are readily prepared via a simple self-doping method, where coal-based graphene quantum dots (GQDs) are used as the carbon and nitrogen resource. PNCNs-900 (obtained at 900 o C) displays good ORR performance, with a half-wave potential ( E 1/2 ) of 0.80 V. It also outperforms commercial Pt/C in terms of stability and methanol tolerance. Experimental investigations and theoretical calculations prove that the PNCNs-900 increased ORR electrocatalytic activity is responsible for the synergistic effect of the large number of defects and graphitic N. Meanwhile, its higher electrocatalytic activity for ORR is also benefited from the porous lamellar structure, which facilitates the mass transfer process. Our work proposes a novel approach to develop effective ORR catalysts and for high value-added utilization of coal resources