Modification of TiO₂Network Structures Using a Polymer Gel Coating Technique

Abstract

A variety of polymer gels with different chemical composition, architecture, porosity, and surface area have been used as templating materials for the fabrication of porous TiO2 networks. Titanium isopropoxide was incorporated in the bicontinuous polymer structure where hydrolysis and condensation reactions were carried out, producing a hybrid of polymer and amorphous titania. Calcination of this hybrid resulted in the formation of a continuous, purely inorganic network of either the anatase or rutile crystal phase, with the individual titanium dioxide particles contacting a number of neighbors, thereby forming a continuous three-dimensional structure. The resulting networks have vastly different structures, with porosities as high as 99% and surface areas ranging from 5 to 100 m2 g-1. These structures may be of importance to various fields of research, including photovoltaics and photocatalysis, because the open “coral-like” network structure of the titanium dioxide allows high access of the titanium dioxide surface to the reaction medium. The potential of the gel coating technology for the construction of more complex chemical systems was illustrated by the assembling of a noble metal/oxide semiconductor hybrid where homogeneously dispersed platinum nanoparticles are integrated within the TiO2 network. Preliminary studies have shown the titanium dioxide materials to exhibit 75% of the photocatalytic activity of Degussa P25.

HRTEM observation of the monoclinic-to-tetragonal m-t) phase transition in nanocrystalline ZrO2

“…A templating procedure [42] was used for the synthesis of the CuO/ZrO 2 material, which involved the use of a polymer gel template [43]. This particular template was an acrylamide/glycidyl methacrylate polymer formed in an aqueous Tween-60 (Aldrich) solution at 55 °C.…”

Hydrothermal synthesis of titanium dioxides from peroxotitanate solution using different amine group-containing organics and their photocatalytic activity

“…Organic modifiers, such as hydroxyl group-containing [9,10], carboxylate group-containing [11][12][13], and amine group-containing organics [14] are widely used in synthesis of nanosized TiO 2 to regulate their final morphology and hence their properties. The basis of such methods is the employment of organics with different types of functional groups to produce a desired product with the required shapes and interface structures of organic modifiers with crystal surface.…”

Mesoporous Anatase TiO2 Beads with High Surface Areas and Controllable Pore Sizes: A Superior Candidate for High‐Performance Dye‐Sensitized Solar Cells

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Mesoporous titania-based materials with a crystalline framework, high surface area and tunable pore size have received significant research attention due to the range of applications for such materials: photocatalysis, energy storage and conversion, electrochromic and sensing fields.[1] For a variety of practical applications, the fabrication of desired morphologies and textures is important as well as control in crystallinity, porosity and composition.[2] Mesoporous titania films, [3] beads, [4] monoliths, [5] networks, [6] and tubes [7] have been prepared via different synthesis strategies. Of particular interest are monodisperse TiO 2 beads with a submicrometer-sized diameter, because of their relatively high refractive index and comparative particle sizes to optical wavelengths, which make them ideal candidates for photon-related applications such as photocatalysis, [4c-g] dyesensitized solar cells (DSSC), [4h] and photonic crystals.

[8]

As a promising alternative to conventional silicon-based solar cells, high performance DSSCs have been extensively studied in recent years.

[9] For an efficient DSSC, the porous electrode composed of anatase phase TiO 2 nanocrystals (% 20 nm) is essential due to the high internal surface area which maximizes the uptake of the dye molecules, thereby giving rise to DSSCs with large current density and high photon-to-current conversion efficiency.

[10] However, such TiO 2 nanocrystal films usually show high transparency and negligible light scattering due to the small particle size and this results in poor light-harvest.

[11] One approach to enhance the light-harvesting capability of the TiO 2 electrodes, without sacrificing the accessible surface for dye loading, is the use of submicrometer-sized TiO 2 beads with abundant mesopores.

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