The effect of water on the performance of TiO2 in photocatalytic selective alkane oxidation

Deactivation of TiO2 is hampering practical implementation of photocatalytic alternatives for energetically intensive selective oxidation processes. In the present study, humidification of the air stream is demonstrated to be a solution to this problem for well-defined photocatalysts, such as Solaronix TiO2, in selective oxidation of cyclohexane. Water establishes enhanced product desorption and stimulates decomposition of deactivating surface carboxylate species, as clearly demonstrated by ATR-FTIR spectroscopy. For high surface area TiO2, such as Hombikat UV100, water molecules adsorb too strongly, and addition of water vapor to the air stream is detrimental to catalyst performance.

In-situ ATR-FTIR spectroscopy shows the absence of formation of deactivating species on anatase of high crystallinity when using humid air as oxidant in the liquid-phase photocatalytic oxidation of cyclohexane to cyclohexanone. The combination of beneficial surface chemical and opto-electronic properties of TiO2 and humid air allows continuous cyclohexanone production.Figure optionsDownload high-quality image (73 K)Download as PowerPoint slideResearch highlights
► Deactivation hampers practical implementation of selective photocatalytic oxidation.
► Water stimulates product (cyclohexanone) desorption.
► Water reduces accumulation of deactivation species on optimized TiO2 surfaces.