Nanoparticulate TiO₂–Al₂O₃ Photocatalytic Media: Effect of Particle Size and Polymorphism on Photocatalytic Activity

Abstract

Impregnation of size-selected titanium-oxo-alkoxy nanoparticles into monolithic ultraporous alumina (UPA) permits nanoparticulate photocatalytic media with an extended activity into the high-temperature range up to 1000 °C, which is explained by anatase TiO2 phase stability due to the inhibited nanoparticles aggregation. In this Article we report on the effect of the nanoparticle polymorphism and size on the photocatalytic ethylene gas decomposition. Use of UPA supports of γ, θ, and α polymorphs, covered with silica or not, and thermal treatment at different temperatures allow modification of the nanoparticles size and crystalline composition. In all cases, the interaction between titania and UPA support is found to affect the polymorph stability. In particular, a separating layer of silica increases the temperature of the anatase-rutile transformation. The main conclusion is that anatase nanoparticles exhibit the higher activity compared to rutile and composite anatase/rutile nanoparticles. The rutile activity strongly decreases with size 2R ≥ 5 nm, while that of anatase nanoparticles does not appreciably change for sizes 5 nm ≤ 2R ≤ 10 nm. The material activity strongly decreases when rutile phase is nucleated onto the anatase one.

Governing Chemistry of Cellulose Hydrolysis in Supercritical Water

“…Ultraporous aluminas (UPA) 1, 2 attract considerable interest because of their potential applications in catalysis, filtration, optoelectronics, photonics, etc. They serve as excellent supporting matrixes for active components in the form of monolayer molecules and single nanoparticles 3–5. Because of an exceptionally low impurity concentration, these materials do not contaminate supported nanoparticles during thermal treatment up to 1000 °C.…”

Physicochemical and electrorheological properties of titanium dioxide modified with metal oxides

“…In addition to the traditional areas of applica tion (pigments and fillers for elastomers), new fields of practical use are arising, such as fillers for electrorheo logical fluids (ERFs) [1][2][3][4] and photocatalysts [5][6][7][8][9][10]. The efficiency of titanium dioxide application is determined by its characteristics, such as dispersity, surface state, and electrophysical properties (conduc tivity, the presence of charge carriers, their mobility, etc.…”

Hierarchical 3D TiO2 Nanotube Arrays Sensitized by Graphene Oxide and ZnxCdyS for High Performance Photoelectrochemical Applications

“…Moreover, research efforts have been made to select the most suitable materials as substrates of electrodes, by considering the physical properties which include conductivity, flexibility, integration with membranes, etc., because these properties can significantly affect the photocatalytic activity of TiO 2 . Several substrates have been investigated as the photocatalyst immobilization such as FTO glass, carbon paper, porous alumina ceramic, etc. In particular, attention has been paid to the use of highly ordered TiO 2 nanotube arrays (TNTAs) films grown by anodization on titanium foil with high specific surface areas .…”