Inorganic Macroporous Films from Preformed Nanoparticles and Membrane Templates: Synthesis and Investigation of Photocatalytic and Photoelectrochemical Properties

Abstract

Colloidal dispersions of titania, zirconia, tin oxide, indium oxide, and ceria have been successfully used to impregnate membrane templates and form the respective metal oxide (MO) porous films. The use of alumina and iron oxide sols in the same procedure, however, resulted in compact structures. By mixing different nanoparticle solutions before impregnation, final inorganic films containing two metal oxides, of variable metal oxide ratios, were obtained. The porous inorganic materials were analyzed in terms of surface area, pore size, film thickness, and crystallinity. The mechanism of nanoparticle infiltration and particle adsorption to the template walls is proposed based on the stability of the inorganic film and a study of the influence of either the sol concentration or washing times on the amount of inorganic substance incorporated in the hybrid material. The photocatalytic decomposition of an organic pollutant, 2‐chlorophenol, was demonstrated for the porous titania material along with the structures containing mixtures of titania with zirconia, indium oxide, and tin oxide. A ratio of 9:1 TiO2/MO gave the highest photocatalytic activity, which was higher than the activity of Degussa P25 for the TiO2/In2O3 and TiO2/SnO2 systems under the same conditions. The titania films have also been attached to substrates—glass or indium tin oxide (ITO) surfaces—and the photoelectrochemical properties of the porous film attained. A comparison with a spin‐coated titania film (prepared from the same colloidal dispersion) showed that the structured porous inorganic film has two times the photoelectrochemical efficiency as the spin‐coated film.

Nanocrystalline TiO2 Photocatalytic Membranes with a Hierarchical Mesoporous Multilayer Structure: Synthesis, Characterization, and Multifunction

“…Sol Preparation: Common sol-gel methods employ direct water addition and lead to the precipitation of amorphous particles with uncontrolled structure that are then peptized in acidic conditions to make a homogeneous sol [38]. An acetic acid-based sol-gel method, where water molecules released from the esterification reaction of acetic acid with isopropyl alcohol during synthesis, was utilized instead of directly adding water [39].…”

Degradation of Hazardous Dyes in Wastewater using Nanometer Mixed Crystal TiO2 Powders under Visible Light Irradiation

“…However, the band gap of anatase TiO 2 is about 3.2 eV, so it can not utilize visible light efficiently. In order to improve the photocatalytic activity and enhance the absorption ability for visible light, many reformative methods for nanometer anatase TiO 2 powder were adopted such as doping transition-metal ions (Diebold 2003;Nagaoka et al 2002) combination of other narrow band-gap semiconductor materials (Tryba et al 2005;Kamat 1993;Yu et al 2003) and aggradation of noble metals (Shchukin and Caruso 2003). These methods indeed make the range of absorption wavelength of nanometer anatase TiO 2 powder be extended to visible light, whereas, they suffer from the thermal instability, costly equipments, expensive raw materials and complicated treatment process (Asahi et al 2001).…”

Photocatalytic degradation of dyestuff wastewater under visible light irradiation using micron‐sized mixed crystal TiO2 powders

“…Many reformative methods have been adopted such as doping of transitionmetal ions, 6,7 coupling with other narrow band-gap semiconductors 8,9 and depositing of noble metals. 10 Also, some special methods during preparation and treatment of TiO 2 photocatalyst were used such as ultraviolet light irradiation, ultrasonic dispersion and H 2 O 2 dipping. 11 Research results showed that these methods can extend the absorption range of anatase TiO 2 powder to visible light, however, they suffer from thermal instability, expensive raw materials and complicated treatment processes.…”