Photoinduced decomposition of acetaldehyde on a reduced TiO2(110) surface: involvement of lattice oxygen
We have investigated the photo-induced decomposition of acetaldehyde (CH3CHO) on TiO2(110) at 400 nm using temperature programmed desorption (TPD) and time of flight (TOF) methods. Formate (HCOO−) and acetate (CH3COO−) products have been detected. The initial step in the decomposition of CH3CHO on TiO2(110) is the formation of a CH3CHO bidentate intermediate in which the carbonyl O atom of CH3CHO is bound to the five-fold-coordinated Ti4+ lattice site (Ti5c) and the carbonyl C atom is bound to a nearby bridge-bonded oxygen (BBO) atom. During 400 nm irradiation, the decomposition of the CH3CHO bidentate mainly occurs through two parallel pathways. Part of the CH3CHO bidentate on the surface undergoes a facile photoreaction to form formate by ejecting the methyl radical of CH3CHO into gas phase. The remaining CH3CHO bidentate reacts on the surface to produce acetate by transferring the H atom of –CHO to a BBO site or by ejecting the H atom into the vacuum. Thus we have found that BBO atoms are intimately involved in the photo-induced decomposition of CH3CHO on TiO2(110).