Visible light-responsive radial TiO 2 mesocrystal photocatalysts for the oxidation of organics

• Published in: Catalysis science & technology Vol. 13; no. 16; pp. 4581 - 4589
• Main Authors: Tada, Hiroaki, Akita, Atsunobu, Naya, Shin-ichi
• Format: Journal Article
• Language: English
• Published: 14.08.2023
• ISSN: 2044-4753; 2044-4761
• DOI: 10.1039/D3CY00195D

Radial TiO 2 mesocrystals (rad-TiO 2 MCs), the so-called “sea urchin-like microspheres”, usually consisting of rutile TiO 2 nanorods with a length of several microns and a diameter of several tens of nanometers, are very promising photocatalyst materials due to the efficient light harvesting ability, large surface area, and easy separation from reaction solution. The key to actually making use of rad-TiO 2 MCs with a high potential as the base material of practical photocatalysts is the reduction of synthesis temperature and time and the simultaneous impartation of the high activity for multiple electron-oxygen reduction reaction (ORR) and visible-light responsiveness to them. This minireview highlights recent progress on the hot topics through the surface modification by Au nanoparticles (Au/rad-TiO 2 MCs) and extremely small iron oxide clusters (FeO x /rad-TiO 2 MCs) acting as both photosensitizer (or oxidation sites) and electrocatalyst for multiple electron-ORR (or reduction sites). Subsequent to the introduction, the synthesis of rad-TiO 2 MCs by a seed-assisted hydrothermal method is described. The fundamental parts deal with the optical and multiple electron-ORR properties of Au/rad-TiO 2 MCs and FeO x /rad-TiO 2 MCs and the redox reaction site separation mechanism unique to the 3D structure. Then, the applications of the rad-TiO 2 MC-based photocatalysts to the oxidation of organics and other important reactions are explored. Finally, the conclusions are summarized with the advantages of rad-TiO 2 MCs over the conventional TiO 2 particles clarified, and some future subjects are described.