Thermal behaviour, kinetics and mechanisms of CO2 interactions with graphene: An atomic scale reactive molecular dynamic study

Atomic scale understanding of gasification interactions between graphene and CO2 is presently very limited. Extensive reactive force field molecular dynamics simulation studies were carried out on interactions of pristine (Pr) and a monovacancy (MV) graphene with CO2 in the temperature range (4100–5000 K). Gasification kinetics showed a non-linear behaviour with temperature; abnormal thermal behaviour was observed in the intermediate (4200–4400 K) temperature region. Gasification rates were found to be substantially lower in this region due to the formation of relatively stable intermediate structures. Three stages were used to describe the whole reaction process. The first stage involved the formation of defects as 5-membered and 7-membered rings; carbon bonds near these defects tended to elongate or break forming voids or cavities. In the second stage, the carbon chains were broken by interaction with O or CO2, leading to the formation of carbonyl groups and active carbon sites with dangling bonds. In the third stage, a number of CO2 molecules or O atoms were adsorbed on the active carbon sites releasing CO and enhanced gasification. The presence of a monovacancy promoted reaction kinetics only at relatively low temperatures with little influence at higher temperatures.