The role of substitutional boron in carbon oxidation

An experimental and theoretical study of carbon oxidation in the presence of substitutionally doped boron has been carried out. The effects of boron loading, reaction temperature and degree of burnoff were analyzed for a range of carbon materials. Both inhibiting and catalytic effects were observed. Several semiempirical molecular orbital modeling approaches were used in an attempt to rationalize these intriguing experimental findings in terms of electronic effects in the graphene layer. In particular, a critical analysis of the key adjustable parameters was performed. The oxidation results were discussed in terms of a balance between three potentially competing effects of substitutional boron: (a) reduced total electron density; (b) decreased contribution of delocalized pi electrons to the electron density of the remaining carbon atoms; and (c) sigma electron localization on carbon atoms due to the higher electronegativity of carbon with respect to boron. (C) 1998 Elsevier Science Ltd. All rights reserved.