Diffusion of CO2 on the Rutile TiO2(110) Surface

The diffusion of CO2 molecules on a reduced rutile TiO2(110)-(1x1) surface has been investigated using scanning tunneling microscopy (STM) and density functional theory (DFT) calculations. The STM feature associated with a CO2 molecule at an oxygen vacancy (V-O) becomes increasingly streaky with increasing temperature, indicating thermally activated CO2 diffusion from the V-O site. From temperature-dependent tunneling current measurements, the barrier for diffusion of CO2 from the V-O site is estimated to be 3.31 +/- 0.23 kcal/mol. The corresponding value from the DFT calculations is 3.80 kcal/mol. In addition, the DFT calculations give a barrier for diffusion of CO2 along Ti rows of only 1.33 kcal/mol.