Photocatalytic activity of TiO2 films on Si support prepared by atomic layer deposition

• Deposition of TiO2 films on Si(1 0 0) surface has been achieved applying ALD.
• Properties of films were tuned varying deposition temperature and number of cycles.
• Photocatalytic oxidation of terephthalic acid, Azur B and herbicides was observed.
• OH
• is responsible for 2,4,5-T oxidation, while various ROS—for 2,4-D degradation.
• Optimal deposition parameters depend on oxidation pathways involving various ROS.

TiO2 films were deposited on the native oxide covered Si(1 0 0) with ALD method. The films were grown applying various numbers of deposition cycles at different temperatures. The resulting coatings possessed different thickness, crystallinity, morphology and roughness. The photocatalytic activity of the films has been studied in the presence of terephthalic acid, Azur B and two herbicides: 2,4-dichlorophenoxyacetic acid and 2,4,5-trichlorophenoxyacetic acid. Coatings deposited at 350 °C (anatase–rutile composites) show the highest activity in the process of TA oxidation (the highest efficiency of hydroxyl radical generation). The influence of film thickness on photoactivity is more complex and depends on the mechanism of processes to be photocatalysed.

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