Photocatalytic reforming of C3-polyols for H 2 production. Part II. FTIR study on the adsorption and photocatalytic reforming reaction of 2-propanol on Pt/TiO 2

Abstract

The adsorption behavior and the photocatalytic reforming (PR) process of 2-propanol over Pt (1wt.%)/TiO 2 (PT) photocatalyst have been investigated by Fourier transform infrared (FTIR) spectroscopy. Both the adsorption complexes and the reforming intermediates formed on the PT and the gas-phase were determined and identified by FTIR spectra. The results indicated that the first layer surface of the PT mainly consisted of chemisorbed 2-propanol (Ti-OCH(CH 3) 2) through the condensation of 2-propanol with surface Ti-OH or dissociative adsorption with undercoordinated Ti atoms, while the second layer consisted of physisorbed 2-propanol by interaction with the chemisorbed one or the formed H 2O via hydrogen-bond. Under UV irradiation, a rapidly deprotonation of 2-propoxide occurred by the attack of holes (h +) and resulted in the formation of acetone, which was then slowly oxidized to acetate and formate species by the hydroxyl radicals (OH). The carboxylates finally decarboxylate over the PT to evolve CO 2 and CH 4 via the photo-Kolbe reaction. According to the results, a reforming mechanism was proposed. The role of the OH groups contained in 2-propanol and its intermediates were found to serve as anchors for their adsorption and to involve the formation of h + transport ways. © 2011 Elsevier B.V.