Coadsorption properties of CO2 and H2O on TiO2 rutile (110): A dispersion-corrected DFT study

Adsorption and reactions of CO2 in the presence of H2O and OH species on the TiO2 rutile (110)-(1x1) surface were investigated using dispersion-corrected density functional theory and scanning tunneling microscopy. The coadsorbed H2O (OH) species slightly increase the CO2 adsorption energies, primarily through formation of hydrogen bonds, and create new binding configurations that are not present on the anhydrous surface. Proton transfer reactions to CO2 with formation of bicarbonate and carbonic acid species were investigated and found to have barriers in the range 6.1-12.8 kcal/mol, with reactions involving participation of two or more water molecules or OH groups having lower barriers than reactions involving a single adsorbed water molecule or OH group. The reactions to form the most stable adsorbed formate and bicarbonate species are exothermic relative to the unreacted adsorbed CO2 and H2O (OH) species, with formation of the bicarbonate species being favored. These results are consistent with single crystal measurements which have identified formation of bicarbonate-type species following coadsorption of CO2 and water on rutile (110). (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4739088]