Synthesis and photo-catalytic properties of $TiO_2$ Nanoparticles

Abstract

Titanium dioxide $(TiO_2)$ particle is a promising candidate photo-catalyst. The $TiO_2$ photo-catalysis is a photon-assisted electrochemical reaction that proceeds on a small $TiO_2$ particle. The $TiO_2$ particle (photo-catalyst) is used to generate electron-hole pairs under photon irradiation. The photo-generated electronic carriers can be used to directly or indirectly convert reducible and oxidizable pollutants to less harmful products or to immobilize them on the particle surface. In the photo-catalysis with $TiO_2$ nanoparticles, one of drawbacks is the difficulty in handling and recycling them during synthesis and photo-catalytic applications, because their surface is highly activated and size is small. In the present study, a new idea was suggested to improve the low handling and recycling ability of $TiO_2$ nanoparticles with using a micrometer-sized secondary particle with primary nanoparticles, and effects of each internal factors (size of secondary particle, fraction of crystallization, surface area, crystallinity, nanoparticle size, nanoparticle shape, synthesis route, surface hydroxyl radical, and $SnO_2$ deposition) on photo-catalytic activity were investigated, so as to extract necessary conditions that $TiO_2$ particles with high photo-catalytic activity must have. In the present study, six kinds of $TiO_2$ particles were prepared by properly combining hydrolysis and condensation reactions, hydrothermal crystallization, and calcination processes; (ⅰ) pure spherical particles, (ⅱ) pure nanoparticles, $SnO_2-deposited$ spherical particles, Fe-doped spherical particles, Ag-deposited spherical particles, and Pt-doped spherical particles. And, photo-catalytic activity was measured by monitoring chlorine ions or hydrogen ions generated during the photo-catalysis chloroform. Photo-catalytic activity highly depended on the materials characteristics and processing conditions; (ⅰ) Secondary spherical particles with primary nanoparticles have...