In situ IR study of surface hydroxyl species of dehydrated TiO2: towards understanding pivotal surface processes of TiO2 photocatalytic oxidation of toluene

Abstract

The surface species on P25-TiO(2) were characterized by FTIR after evacuation at 50-550 °C. The functions of OH groups on P25-TiO(2) catalysts have been tested by the adsorption and photooxidation of toluene in an in situ IR cell. FTIR studies show that the hydroxyl species on P25-TiO(2) are clearly temperature-dependent and P25-TiO(2) has six isolated hydroxyls with bands at 3734, 3715, 3688, 3671, 3658 and 3640 cm(-1). The OH groups on P25 play different roles in the photo-oxidation process: surface hydroxyls with bands at 3688, 3671, 3658 and 3640 cm(-1) act as adsorption sites while surface hydroxyls with bands at 3734 and 3715 cm(-1) act as sources of the ˙OH radical.

Role of Adsorbed Water on Charge Carrier Dynamics in Photoexcited TiO2

“…This was accompanied by the appearance of the band at 3734 cm –1 which was attributed to terminal hydroxyls of the anatase TiO 2 42,43 and was not observed in the untreated sample (Figure 2). Another difference between samples i and v was the rearrangement of the O–H bands under 325 nm irradiation.…”

Contaminant effects on the photo-oxidation of greywater over titania film catalysts

“…Comparing the photodegradation rate of methyl Under normal conditions, the TiO 2 surface is hydrated, with both adsorbed water and various surface OH groups, the combination of which partly determines photocatalytic behaviour. However, after firing at high temperature, TiO 2 is both dehydrated and dehydroxylated [43,44]. Both films, Ti(H 2 O) and Ti(MO), were dehydrated at 500 • C for 3 h before initial use.…”

First Principles Study on the Interaction Mechanisms of Water Molecules on TiO2 Nanotubes

“…The adsorption of water on TiO 2 , especially in the dissociated state, can be significantly enhanced by the presence of fourfold coordinated Ti atoms at the step edge of the surface, due to the easy transfer of charge from the water molecule to the TiO 2 [31]. The photocatalytic properties of TiO 2 can be affected by the adsorption of hydroxyl, and thus it is important to understand the interaction mechanisms between the water/hydroxyl and the TiO 2 surface [33]. There are a variety of distributions of OH groups due to the influence of complex adsorption states of water molecules.…”

“…There are a variety of distributions of OH groups due to the influence of complex adsorption states of water molecules. Two types of hydroxyls are found to adsorb on the TiO 2 surface, which could be classified as thermally unstable and thermally stable (isolate hydroxyl groups) in terms of thermostability [33,34,35,36]. The adsorption bands of these hydroxyls are greatly affected by the crystal structure of TiO 2 and the evacuation temperature.…”

“…The adsorption bands of these hydroxyls are greatly affected by the crystal structure of TiO 2 and the evacuation temperature. The hydroxyls play different roles in the photo-oxidation process [33], but the chemical environment of hydroxyls on the TiO 2 surface are still deficient.…”