Adsorption and Reactivity of CO2 on Defective Graphene Sheets

Density-functional calculations have been performed to investigate the adsorption of CO2 on defected graphite (0001) represented by a single graphene sheet. The interaction with a vacancy defect gives a computed molecular binding energy of similar to 136 meV in a strong physisorbed state. Subsequently, chemisorption by lactone group formation will occur after overcoming a barrier of similar to 1 eV relative to the gas phase, with an exothermicity of about 1.4 eV. Further reaction paths from this chemisorbed state lead to dissociation of the CO2 through the formation of epoxy groups followed by oxygen recombination and desorption of O-2, after overcoming successive energy barriers of similar to 0.9 and similar to 1.0 eV. The global minimum ("O-2 desorbed + graphene sheet") entails an energy release of about 3.4 eV with respect to the initial state.