Interaction of CO2 with TiO2/reduced graphene oxide as superior catalysts: Dispersion-corrected density functional theory simulation

Abstract

Interaction of CO2 with the anatase TiO2 slab, nano-TiO2 cluster and nano-TiO2/reduced graphene oxide (rGO) was explored by density functional theory simulations. Two orientations, namely (001) and (100) directions, were examined for an approaching CO2 molecule to the surfaces. The energetically favorable state corresponds to a CO2 molecule adsorbed in the (001) direction for all the considered substrates. The interaction energies of adsorbed CO2 on the TiO2 slab, nano-TiO2 cluster, and nano-TiO2-rGO (on the nano-TiO2 cluster attached to the rGO) surfaces were determined to be about −5.007, −11.643, and −13.025 kcal/mol, respectively. Interaction properties were identified by the high-level MP2 calculations and the AIM theory analysis. Finally, for the adsorbed CO2 on the nano-TiO2-rGO, density-functional tight-binding (DFTB) molecular dynamics simulation were carried out and the results showed that CO2 absorption strength was enhanced on the (001) nano-TiO2 at room temperature by bonding of either O atom or C atom to the surface Ti and O atoms. It is found that nano-TiO2-rGO was more effective for CO2 adsorption than both the bulk TiO2 slab and free nano-TiO2 cluster.