TiO₂ Colloids Laser-Treated in Ethanol for Photocatalytic H₂ Production

Laser irradiation in liquid is a green, low cost, and tunable technique that can be used in order to improve solar photocatalytic activity of inorganic semiconductors. The interaction between the semiconductor and the dispersing medium is a key parameter to be investigated before and after the laser modification, since it can affect the final morphological and chemical–physical properties of the material. In this work, titania colloids were properly modified by UV laser irradiation process in different solvents. The interaction of solvents (water or ethanol) with titania surface was investigated by spectroscopic characterizations and ab initio calculations based on structure predictions at a density functional theory level. Both solvents interact with oxygen vacancies on titania surface, resulting in a partial or complete passivation of defects by water and ethanol molecules, respectively. The modified samples showed an increase of the photocatalytic hydrogen production under both UV and solar light irradiation. The use of ethanol as solvent during the laser process was found to be the best choice to improve the activity of TiO2 sample under visible light. The as-developed strategies may open up an interesting avenue for designing semiconductor materials with visible light absorption properties and enhanced photocatalytic performance.