Crucial role for oxygen functional groups in the oxygen reduction reaction electrocatalytic activity of nitrogen-doped carbons

Generally, a significant amount of oxygen functional groups (OFGs) usually exist on the surface of nitrogen-doped carbons. Unfortunately, the role of OFGs on the oxygen reduction reaction (ORR) electrocatalytic activity of nitrogen-doped carbons is rarely discussed. Herein, we report that the OFGs play a crucial role on the ORR electrocatalytic activity of nitrogen-doped carbons. A nitrogen doped carbon foam (NCF) containing OFGs was prepared by pyrolysis of melamine foam. The species of the OFGs were then tuned by chemical reduction, and their effects on the ORR electrocatalytic activity of the NCF were investigated by electrochemical measurements, X-ray photoelectron spectroscopy and solid-state NMR spectroscopy. Results showed that the ORR electrocatalytic activity of the NCF greatly decreased after chemical reduction. The OFGs in the form of quinone were found to be crucial for the ORR electrocatalytic activity of the NCF. This study not only provided a new and effective strategy for investigating the effect of OFGs on the ORR electrocatalytic activity of nitrogen-doped carbons, but also presented a new insight into understanding their electrocatalytic mechanism. (C) 2018 Elsevier Ltd. All rights reserved.