Aluminium(iii) adsorption: a soft and simple method to prevent TiO₂deactivation during salicylic acid photodegradation

Abstract

Deposition of poisoning species on TiO2 during salicylic acid photodegradation can be halted when Al(III) has been previously adsorbed on the catalyst surface; this widens the application of photocatalysis to more concentrated solutions.

A surface science perspective on TiO2 photocatalysis

“…Surface Fe 3+ cations enhanced maleic acid photooxidation [1455] [1458]. Adsorbed Al 3+ cations diminished the build-up of strongly bound surface intermediates that inhibited salicylic acid photodecomposition on TiO 2 [1459]. In a slightly different sense, addition of Fe 3+ to the surface of A was shown to inhibit formation of surface sites that can initiating the A-to-R phase transformation [1458].…”

Review of the anatase to rutile phase transformation

“…It has been suggested that cations of small radii and low valence accelerate the transition to rutile owing to the increase in oxygen vacancies that result from the assumed substitution of Ti 4? ions with cations of lower valences [43,109,157,164,165]. Charge neutrality thus requires an increase in the level of oxygen vacancies and/or the formation of Ti interstitials of lower valence [82,172].…”

“…• Reduction of the band gap in titania [18,151] • Introduction of mid-gap states [56,163] • Improvement in charge carrier separation [68,73] • Increase in the levels of surface-adsorbed species (e.g., hydroxyl radicals) [43] It often is not appreciated that all titania is contaminated with some levels of impurities. The presence of unintentional impurities or intentional dopants has a strong effect on the kinetics of the anatase to rutile transition [170].…”

“…• Built Environment Self-cleaning coatings [34,38,39,[41][42][43][44][45][46][47][48][49][50]. Non-spotting glass [47,51].…”

Surface-Modified Photocatalysts

“…This could limit the application of photocatalysis to high ionic strength media, like seawater [78]. However, adsorbed Al 3+ cations halted poisoning caused by adsorption of strongly bound surface intermediates on TiO 2 during salicylic acid photodegradation [79]. In anatase/water systems under bandgap irradiation, both the organic substrate (formate) oxidation initiated by photogenerated valence band holes and the formation of hydrogen peroxide from O 2 reduction (by conduction band electrons) are strongly influenced by the presence of Zn 2+ cations [80].…”