Selectively nitrogen-doped carbon materials as superior metal-free catalysts for oxygen reduction.

Doping with pyridinic nitrogen atoms is known as an effective strategy to improve the activity of carbon-based catalysts for the oxygen reduction reaction. However, pyridinic nitrogen atoms prefer to occupy at the edge or defect sites of carbon materials. Here, a carbon framework named as hydrogen-substituted graphdiyne provides a suitable carbon matrix for pyridinic nitrogen doping. In hydrogen-substituted graphdiyne, three of the carbon atoms in a benzene ring are bonded to hydrogen and serve as active sites, like the edge or defect positions of conventional carbon materials, on which pyridinic nitrogen can be selectively doped. The as-synthesized pyridinic nitrogen-doped hydrogen-substituted graphdiyne shows much better electrocatalytic performance for the oxygen reduction reaction than that of the commercial platinum-based catalyst in alkaline media and comparable activity in acidic media. Density functional theory calculations demonstrate that the pyridinic nitrogen-doped hydrogen-substituted graphdiyne is more effective than pyridinic nitrogen-doped graphene for oxygen reduction.