Photooxidation of Formic Acid vs Formate and Ethanol vs Ethoxy on TiO_2 and Effect of Adsorbed Water on the Rates of Formate and Formic Acid Photooxidation

摘要

Comparison of photooxidation rates of formic acid and formate on TiO_2 as well as the effect of adsorbed water on formate and formic acid photodecomposition rates have been investigated by Fourier transformed infrared spectroscopy. Adsorbed formic acid and formate are all photooxidized to CO_2 in O_2. Formic acid on TiO_2 shows a photoreaction rate that is roughly 53 times that of formate groups for a same surface concentration. The presence of H_2O can increase formate and formic acid photooxidation rates by a factor colse to 2. In addition, photochemistry of adsorbed ethanol and ethoxy is also compared. It is found that ethanol is important for the formation of acetaldehyde, while ethoxy groups groups are photooxidized to adsorbed acetate, formate, and water. Possible reasons for these differences are discussed.