Study of oxygen isotopic exchange over ultraviolet irradiated anatase samples and comparison with the photooxidation of isobutane into acetone

Abstract

Publication costs assisted by the Centre National de la Recherche Sclentifique Oxygen isotopic exchange (OIE) measurements have been carried out over UV irradiated anatase samples. At room temperature, simultaneous action of Ti02 and UV light is needed for OIE which proceeds via a mechanism involving one oxygen surface atom at a time. For various anatase samples, the photocatalytic activities per unit of catalyst area for OIE and for isobutane oxidation (IOX) into acetone correlate. UV irradiation of a mixture of í-C4H10 and of an excess of 1802 shows that OIE occurs only after IOX. It is inferred that the same dissociated surface oxygen species participate in both reactions.

Surface Chemistry and Interfacial Charge‐Transfer Mechanisms in Photoinduced Oxygen Exchange at O2–TiO2 Interfaces

“…An analogous correlation between POIE and PO was observed by Sato et al for the oxidation of ethane on a home prepared TiO 2 sample calcined at various temperatures, [12] a fact that was attributed by these authors to the participation of photogenerated O À s radicals as active surface species in both mechanisms. The same conclusion was reached by Pichat et al after observing that 18 O 2 ðgÞ does not exchange oxygen atoms with the TiO 2 surface when either isobutane [8] or methanol [18] are present in the gas phase. On the other hand, Muggli and Falconer [17] studied the POIE mechanism between gas-phase 16 2 18 O was present at the TiO 2 surface.…”

“…The time dependence of the isotopic composition of gasphase O 2 during the POIE experiments, first obtained by Pichat et al, [8] is reproduced in Figure 2. Similar experimental results were later obtained by Sato.…”

“…(4) and (5)]: [18] R1 [7,8,12] Pichat et al also found that the POIE activity of different TiO 2 samples was very similar to their activity for isobutane [8] and methanol [18] photo-oxidation. An analogous correlation between POIE and PO was observed by Sato et al for the oxidation of ethane on a home prepared TiO 2 sample calcined at various temperatures, [12] a fact that was attributed by these authors to the participation of photogenerated O À s radicals as active surface species in both mechanisms.…”

“…[8] The observation that POIE does not take place in the presence of isobutane allowed these authors to infer that the same oxygen species of the TiO 2 surface participate in both reactions. More recently, Pichat and co-workers showed that POIE is a very sensitive method for evaluating the mobility of TiO 2 terminal oxygen atoms and understanding their incorporation into gas-phase substrate species during PO interfacial reactions, [18] a subject of primary interest in heterogeneous photocatalysis.…”

In-situ Calibration of the Hydroperoxyl Radical Using an Immobilized TiO2Photocatalyst in the Atmosphere

“…The formation of HO 2 · in a TiO 2 photolysis is well-known. The basic mechanisms are as follows: [17][18][19][20][21][22][23][24][25][26][27] ·− (self-reactions 1-3), this was reported to be potential interference. 10 However, the following experimental results denied this possibility.…”