Selective synthesis of TiO2-based nanoparticles with highly active surface sites for gas-phase photocatalytic oxidation

This work demonstrated the absence of surface terminal hydroxyl groups plays a key role in the photocatalytic oxidation of low concentration volatile organic compounds. Probed by 1H MAS NMR spectroscopy, we showed the synthesis of bare and F-TiO2 nanoparticles with undetectably low content of terminal hydroxyl groups (TiOH) on the surface of TiO2 could be obtained through a sol–gel process. The characterization results by N2 adsorption, XRD, HRTEM, Raman, and XPS show that the bare TiO2 and F-TiO2 have almost identical bulk and surface structural properties. The photocatalytic activity was evaluated by photocatalytic oxidation of acetaldehyde and ethanol. Due to the absence of terminal TiOH in the bare TiO2 and F-TiO2, both materials exhibit 100% photodegradation of acetaldehyde and ethanol. No deactivation was observed during the experimental period of 8 days. The activities surpassed the photodegradation performance of the benchmarking Aeroxide P25 TiO2 under similar conditions (93%). On the bare TiO2, only stoichiometric CO2 production was observed and no detectable by-product existed in the product stream, resulting in no expanded off-odor problems. On the contrary, ethanol photodegradation on F-TiO2 produced minor acetaldehyde as a by-product, but the amount of acetaldehyde produced was still lower than that produced on Aeroxide P25.

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► It corroborates surface hydroxyl groups is vital for defining TiO2 photoactivity.
► We apply this understanding to the synthesis of highly active TiO2 materials.
► The present bare TiO2 exhibits 100% photodegradation of acetaldehyde and ethanol.
► Only stoichiometric CO2 production was observed and no by-products were evolved.