Carbon-Covered Hollow Nitrogen-Doped Carbon Nanoparticles and Nitrogen-Doped Carbon-Covered Hollow Carbon Nanoparticles for Oxygen Reduction

Nitrogen-doped carbon materials are realized as effective electrode materials for oxygen-involved electrochemical devices. Understanding of active sites for adsorption of oxygen molecules is of significant importance for the development of carbon-based electrode materials. Herein, we synthesize two model catalysts named carbon-covered nitrogen-doped hollow carbon nanoparticles and nitrogen-doped carbon-covered hollow carbon nanoparticles by pyrolysis of block copolymer brushes to investigate the active sites for the adsorption of oxygen molecules. The electrocatalytic performance for oxygen reduction reaction (ORR) and carbon dioxide adsorption suggest that carbon atoms are Lewis basic active sites for oxygen adsorption. The coverage of a thin carbon layer on nitrogen-doped carbon materials can increase the surface density of Lewis basic sites for oxygen adsorption and can accordingly improve the electrocatalytic activity toward ORR as confirmed by a positive shift of both onset potential and half-wave potential.