Continuously increasing atmospheric concentrations of CO2 have given rise to great concerns about climate change. Photocatalytic reduction of CO2 to chemicals by solar energy is considered a green and sustainable process. Interactions between CO2 molecules and photocatalysts surfaces are the key factors that affect photocatalytic reduction efficiency. Thus, a better understanding of their reactive species on the TiO2 nanotube (TNT) surfaces by in situ FTIR spectroscopy was studied in the present work. The FTIR absorbance features at 1303cm−1 and 1393cm−1 were associated with carbonate species, e.g., bidentate carbonate on the TNT. Complete desorption of CO2 from the TNT occurred at T>418K. The carboxylate species that were adsorbed on the TNT may conduct the surface reactions enhanced by UV–Vis light to yield low carbon chemicals.
