DFT study of the catalytic effect of Na on the gasification of carbon--CO2

A key question in the study of the CO2-gasification process is the mechanism of the Na-containing catalytically active center. In this study, density functional theory calculation was carried out to examine the catalytic role of Na in two graphite models (armchair-edge and zigzag-edge). Two Na-containing groups (CNa, CONa) were considered in each model. The activation energies for all reaction pathways indicated that Na showed catalytic activity in the dissociative adsorption of CO2 in both of the graphite models. However, in the subsequent desorption of CO, which is the rate-determining step, only the armchair-edge model indicated catalysis by Na. The molecular structures and reduced density gradient analysis showed that, during CO2 dissociative adsorption, the Na atom promoted breakage of the CO bond and weakened the conjugate structure at the aromatic nucleus to release CO.