Ultrafast dynamics of acetone photooxidation on TiO2(110)

Abstract

Using light energy to drive chemical reactions on semiconductor surfaces is the basis for technological applications ranging from the removal of organic pollutants to the generation of renewable solar fuels, yet our understanding of the mechanisms has been hindered by the multistep nature of the process and the wide range of time scales over which it occurs (femtoseconds to seconds). In this work, we use ultrafast laser pump-probe techniques to follow the time evolution of substrate-induced photooxidation of acetone on a titania surface. A UV light at 260 nm initiates carrier-induced fragmentation of adsorbed acetone on a TiO2(110) surface that was pretreated with oxygen. The photoreaction results in the ejection of methyl radicals into the gas-phase that are detected by the probe pulse via resonant multiphoton ionization. The time evolution of the methyl radicals leaving the surface exhibits ultrafast rise times, 300–700 fs, followed by a more gradual rise that plateaus by 10 ps, with faster rates at a low acetone coverage. These results are interpreted in terms of a time-dependent rate expression and a mechanism in which the fragmentation of the acetone surface species is driven by interactions with nonequilibrium, “hot” holes.

Highly Active Nanocrystalline ZnO and Its Photo-Oxidative Properties towards Acetone Vapor

“…However, a detailed and systematic study of the some mechanisms, in particular, the photochemical oxidation of acetone, on the ZnO surface has not yet been carried out. An analysis of the literature shows that studies of the gas-phase photo-oxidation of acetone has mainly focused on TiO 2 and TiO 2 -based materials [ 57 , 58 , 59 ], while information on the photo-oxidation of acetone on the ZnO surface is limited. For example, Ref.…”

Size and Coverage Effects of Ni and Pt Co-Catalysts in the Photocatalytic Hydrogen Evolution from Methanol on TiO2(110)

“…Laser ablation cluster sources have already shown their value in many thermal catalytic studies by revealing crucial effects of cluster size, coverages, and material properties. , In photocatalysis, however, similar studies are scarce and cluster size effects remain largely unexplored, even though there is evidence for a significant impact . Co-catalyst-loaded TiO 2 (110) is one of the most commonly employed photocatalytic model systems, especially for H 2 evolution. − In the last decade, several groups have contributed to a fundamental insight into the surface chemistry of titania single crystals, , the material’s charge carrier dynamics, − and the role of the co-catalyst in alcohol photooxidation. ,,,,− It has been shown that Pt, Ni, and other metal clusters serve as co-catalyst to facilitate thermal H 2 evolution during photocatalytic methanol reforming on TiO 2 (110). These metal clusters all fulfill the same purpose as recombination and desorption centers for surface hydrogen species, apparently following the same mechanistic steps. ,,, In principle, this allows for their quantitative comparison as co-catalysts in the thermal hydrogen formation during methanol photoreforming.…”

Antireflective Self-Cleaning TiO2 Coatings for Solar Energy Harvesting Applications

“…Ideally, a coating material for terrestrial solar cell applications should be robust, transparent, antireflective, and capable of self-cleaning itself. Titania (TiO 2 ) is an ideal material due to its excellent physicochemical properties and has been widely investigated in such applications, e.g., high-efficiency solar cells (O'Regan and Grätzel, 1991;Kim et al, 2008), ARCs (Wan et al, 2010;Manea et al, 2013;Salvaggio et al, 2016), and photocatalysis (Fujishima et al, 2000;Fujishima et al, 2008) especially photooxidative self-cleaning (Paz et al, 1995;Muraca et al, 2019). TiO 2 has a bandgap of 3.2 eV and absorbs light in a wide range of frequencies.…”