Adsorption and dissociation of CH ₄ on graphene: A density functional theory study

To investigate the mechanism of the heterogenous reactions during the Chemical vapor infiltration (CVI) process of carbon/carbon composites, the dissociation of CH ₄ on graphene was calculated by density functional theory (DFT). Graphene was used as the adsorption surface in the course of the heterogenous reactions. Based on the energy analysis, the preferred adsorption sites of CH _x (x = 0–4) and H on graphene were obtained. Then, the stable co-adsorption configurations of CH _x /H(x = 0–3) on graphene were located. The calculation results show that CH ₄ , CH ₃ and H prefer to be adsorbed at the top of a carbon atom of graphene, while CH ₂ , CH and C are favorable on the midpoint of a C–C bond of graphene. Transition state (TS) calculation shows that the dissociation of CH ₄ into CH ₃ and H is a rate-determining step. Additionally, by comparing the dissociation of CH ₃ into CH ₂ and H and the formation of C ₂ H ₆ during the dissociation of CH ₄ , it is obvious that the CH ₃ groups are more likely to produce ethane rather than dissociating into CH ₂ and H.