Oxygen migration on the graphene surface. 1. Origin of epoxide groups

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• 作者：Ljubisa R. Radovic^a ; ^b ; ^{lrr3@psu.edu"" rel=""nofollow} ; Alejandro B. Silva-Tapia^b ; Fernando Vallejos-Burgos^b
• 刊名：Carbon
• 出版年：2011
• 出版时间：November 2011
• 年：2011
• 卷：49
• 期：13
• 页码：4218-4225
• 全文大小：1120 K

文摘

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.