CO2 chemisorption on alkalated TiO2(1 0 0)-(1×3) studied with MIES and UPS(HeI)

The CO2 uptake of clean and partially alkalated (K,Cs) TiO2(1 0 0)-(1×3) surfaces was studied under in situ control of metastable impact electron spectroscopy (MIES) and photoelectron spectroscopy (UPS(HeI)) at room temperature. While the clean surface shows no uptake of CO2, it is quite strong for the alkalated surface at room temperature. The work function increase observed during the CO2 uptake signals charge flow from the alkali adsorbates into the lowest unoccupied 2πu MO of CO2. It is suggested that the resulting CO2− intermediate bonds to surface oxygen forming a carbonate (CO3) complex. The results are compatible with the assumption that CO2 chemisorbs close to those oxygen anions that have alkali atoms associated with themselves.