Dual-components modified TiO2 with Pt and fluoride as deactivation-resistant photocatalyst for the degradation of volatile organic compound

TiO2 nanoparticles modified with surface platinization or/and surface fluorination (Pt/TiO2, F-TiO2, and F-TiO2/Pt) were prepared to test their durability as an air-purifying photocatalyst. Toluene was selected as a target substrate for this test. Although Pt/TiO2 showed higher photocatalytic degradation activity than bare TiO2, Pt/TiO2 underwent rapid deactivation during repeated degradation cycles. F-TiO2 was deactivated to a lesser degree but its initial photocatalytic degradation activity was lower than bare TiO2. On the other hand, F-TiO2/Pt exhibited the highest photocatalytic activity and durability for toluene degradation. The surface fluorination that should replace the hydroxyl groups on TiO2 surface facilitates the formation of mobile OH radicals instead of surface -bound OH radicals. The surface platinization enhances the lifetime of charge carriers and makes more holes efficiently react with adsorbed water molecules. Through the remote photocatalytic oxidation of stearic acid and coumarin coated on a glass plate that was separated from the photocatalyst film with a small air gap (50 tun), it was observed that F-TiO2/Pt film generated the largest amount of mobile OH radicals that migrate through the air gap. The photocatalytic oxidation mediated by mobile OH radicals efficiently hindered the deposition of carbonaceous intermediates on the F-TiO2/Pt surface and increased the mineralization efficiency of VOCs, which consequently increased the durability of photocatalyst during VOC degradation.