Significant Contribution of Intrinsic Carbon Defects to Oxygen Reduction Activity

While the field of carbon-based metal-free electrocatalysts for oxygen reduction reaction (ORR) has experienced great progress in recent years, the fundamental issue of the origin of ORR activity is far from being clarified. To date, the ORR activities of these electrocatalysts are usually attributed to different dopants, while the contribution of intrinsic carbon defects has been explored little. Herein, we report the high ORR activity of the defective carbon nanocages, which is better than that of the B-doped carbon nanotubes and comparable to that of the N-doped carbon nanostructures. Density functional theory calculations indicate that pentagon and zigzag edge defects are responsible for the high ORR activity. The mutually corroborated experimental and theoretical results reveal the significant contribution of the intrinsic carbon defects to ORR activity, which is crucial for understanding the ORR origin and exploring the advanced carbon-based metal-free electrocatalysts.