Photoinduced decomposition of acetaldehyde on a reduced TiO2(110) surface: involvement of lattice oxygen

Abstract

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 (Ti_5c) 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).