Computational Study on Removal of Epoxide from Narrow Zigzag Graphene Nanoribbons

We performed computational studies on the removal of an epoxide group from oxidized zigzag graphene nanoribbons (ZGNRs). Using density functional theory (DFT) calculations, we investigated the reaction mechanisms for the two competing processes, migration and reduction of an epoxide group in the middle of a narrow ZGNR. We found that the relative magnitudes of the barriers for migration and reduction depend on the width of the ZGNR. The reaction barrier for the reduction of an epoxide by CO decreased as the width of the ZGNR increased, while the barrier for migration showed the opposite trend. Moreover, the transition state energies for migration and reduction decreased upon the applied electric field perpendicular to the surface of the ZGNR. Our results illustrate that the removal of an epoxide from a ZGNR by reduction with CO can be facilitated by the application of an external electric field. For narrow ZGNRs, epoxide migration to neighboring sites may compete with the reduction reaction