Modification of C, O, and N Groups for Oxygen Reduction Reaction on an Electrochemically Stabilized Graphene Nanoribbon Surface

There has been a huge debate in the literature over the past few years regarding the groups (C, O, and N groups and their quantities) involved in oxygen reduction reaction on metal-free carbonaceous nanostructured surfaces. The present study shows that the electrochemical stabilization of graphene oxide nanoribbons (GONRs) leads to an increase in the number of quinone groups on the surface of GONR electrodes. These quinone groups are responsible for the high production of HO2-. The percentage decrease observed in HO2- production (in a region of defined potential) is attributed to the presence of pyrrolic-N groups along with epoxy groups on the electrochemically stabilized surface of graphene nanoribbon (GNR) electrodes. The presence of pyrrolic-N groups along with epoxy groups on the electrochemically stabilized surface of GNR electrodes is observed concomitantly with a decrease in the amount of pyridinic-N groups oxidized to N oxides from pyridinic- N groups in addition to a significant decrease in the percent concentration of quinone groups. The combination of pyrrolic-N groups (without ruling out the contribution of pyridinic-N groups, which presented very low percentage content with a total N atomic concentration of only 0.7%) with quinone groups on a nonelectrochemically stabilized GNR surface is responsible for the high production of HO2-.