Facet‐Dependent Performance of Microstructured <scp>S</scp>r<scp>T</scp>i<scp>O</scp>₃ Particles in Photocatalytic Oxidation of Acetone

Photocatalysis is a promising technology for purification of indoor air by oxidation of volatile organic compounds. This study provides a comprehensive analysis of the adsorption and photo‐oxidation of surface‐adsorbed acetone on three SrTiO 3 morphologies: cubes (for which exclusively {100} facets are exposed), {110}‐truncated cubes, and {100}‐truncated rhombic dodecahedrons, respectively, all prepared by hydrothermal synthesis. In situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy shows that cubic crystals contain a high quantity of surface –OH groups, enabling significant quantities of adsorbed acetone in the form of η 1 ‐enolate when exposed to gas phase acetone. Contrary, {110} facets exhibit fewer surface –OH groups, resulting in relatively small quantities of adsorbed η 1 ‐acetone, without observable quantities of enolate. Interestingly, acetate and formate signatures appear in the spectra of cubic, surface η 1 ‐enolate containing, SrTiO 3 upon illumination, while besides acetate and formate, the formation of (surface) formaldehyde was observed on truncated cubes, and dodecahedrons, by conversion of adsorbed η 1 ‐acetone. Time‐Resolved Photoluminescence studies demonstrate that the lifetimes of photogenerated charge carriers vary with crystal morphology. The shortest carrier lifetime (τ 1 = 33 ± 0.1 ps) was observed in {110}‐truncated cube SrTiO 3 , likely due to a relatively strong built‐in electric field promoting electron transport to {100} facets and hole transport to {110} facets. The second lifetime (τ 2 = 259 ± 1 ps) was also the shortest for this morphology, possibly due to a higher amount of surface trap states. Our results demonstrate that SrTiO 3 crystal morphology can be tuned to optimize performance in photocatalytic oxidation.