TY - JOUR
T1 - Oxygen migration on the graphene surface. 1. Origin of epoxide groups
AU - Radovic, Ljubisa R.
AU - Silva-Tapia, Alejandro B.
AU - Vallejos-Burgos, Fernando
N1 - Funding Information:
Financial support for this study was provided by CONICYT-Chile (Fondecyt projects 1060950, 1080334 and PFB-27, CCTE-UDT). Use of the computational facilities at Penn State’s Materials Simulation Center (Jorge Sofo, director) is gratefully acknowledged, as are the many incisive and constructive suggestions received from the reviewers.
PY - 2011/11
Y1 - 2011/11
N2 - It is now a widely accepted fact that oxidized graphene surfaces are populated, to a greater or lesser extent, with epoxide groups. And yet the origin of these groups has heretofore been mysterious. We report the results of a computational (DFT) analysis of this issue carried out by combining the theoretical and experimental knowledge of three seemingly unrelated fundamental processes: (i) formation of pentagon-heptagon pairs (or Thrower-Stone-Wales defects); (ii) surface diffusion of oxygen atoms on the basal plane; and (iii) graphene unzipping by oxygen insertion. We provide thermodynamic and kinetic evidence for the hypothesis that a key intermediate step in the stabilization of free adjacent zigzag sites - before they reconstruct to form an armchair site or become quinone surface functionalities upon dissociative O2 chemisorption - is the formation of an epoxide group in the basal plane. The presence of epoxide groups on the graphene surface is therefore a result of spillover of edge oxygen (e.g., nondissociatively adsorbed O2 on carbene-type sites), mechanistically reminiscent of the extensively investigated migration of carbon in the conversion of phenyl carbene to bicycloheptatriene.
AB - It is now a widely accepted fact that oxidized graphene surfaces are populated, to a greater or lesser extent, with epoxide groups. And yet the origin of these groups has heretofore been mysterious. We report the results of a computational (DFT) analysis of this issue carried out by combining the theoretical and experimental knowledge of three seemingly unrelated fundamental processes: (i) formation of pentagon-heptagon pairs (or Thrower-Stone-Wales defects); (ii) surface diffusion of oxygen atoms on the basal plane; and (iii) graphene unzipping by oxygen insertion. We provide thermodynamic and kinetic evidence for the hypothesis that a key intermediate step in the stabilization of free adjacent zigzag sites - before they reconstruct to form an armchair site or become quinone surface functionalities upon dissociative O2 chemisorption - is the formation of an epoxide group in the basal plane. The presence of epoxide groups on the graphene surface is therefore a result of spillover of edge oxygen (e.g., nondissociatively adsorbed O2 on carbene-type sites), mechanistically reminiscent of the extensively investigated migration of carbon in the conversion of phenyl carbene to bicycloheptatriene.
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U2 - 10.1016/j.carbon.2011.05.059
DO - 10.1016/j.carbon.2011.05.059
M3 - Article
AN - SCOPUS:79961025897
SN - 0008-6223
VL - 49
SP - 4218
EP - 4225
JO - Carbon
JF - Carbon
IS - 13
ER -