Novel Synthesis of the TiO₂(B) Multilayer Templated Films

Abstract

TiO2(B) mesoporous thin films were grown in two steps on the F-doped SnO2 conductive glass substrates. In the first step, a small amount of H3PO4, corresponding to 0.15−0.375 wt % P on TiO2 basis, was introduced into concentrated HCl which was subsequently used for hydrolysis of titanium ethoxide. The hydrolyzed colloidal TiO2 suspension was further mixed with a 1-butanol solution of the amphiphilic triblock copolymer Pluronic P123. The obtained precursor mixture was used for dip coating of FTO substrates. To achieve over 1 μm thick films, dip coating (followed by a thermal treatment at 350 °C/2 h) was repeated several times to produce multilayer films. The films consisted of amorphous TiO2 with small amounts of anatase and TiO2(B). The amorphous part was converted into the TiO2(B) in a simple firing step at 500−550 °C. The formation of TiO2(B) phase was accompanied by a significant increase of the film thickness. The films demonstrated unique behavior during the electrochemical lithium insertion that would qualify them for fast battery or electrochromic smart window applications. The efficiency of multiphase TiO2 films in dye sensitized solar cells depends on the composition of individual films: it increases in the series: anatase/amorphous TiO2 < anatase/TiO2(B) < anatase.

Block copolymer-templated synthesis of highly organized mesoporous TiO2-based films and their photoelectrochemical applications

“…Concentrated hydrogen chloride (HCl, 35-37 wt%) with a HCl/Ti molar ration of 1.6-2.0 is most commonly employed to control the hydrolytic reactivity of titanium alkoxides [16,[44][45][46][47][48]. Other acids, sulfuric acid [49], nitric acid [50][51][52], phosphoric acid [53,54], and acetic acid [14,55,56], have also been used in stabilizing Ti precursor in order to eliminate the accommodation of Cl − in resulting films.…”

“…Recently, mesoporous TiO 2 films with a metastable TiO 2 (B) crystal phase were also synthesized by adding a small amount of H 3 PO 4 into the initial sol solution [53,54]. It seems that the formation of phosphorus-stabilized TiO 2 intermedia is essential to improve their phase transformation into monoclinic TiO 2 (B) at a calcination temperature above 500 • C.…”

“…Recently, Prochazka et al [53] synthesized mesoporous TiO 2 films with bi-crystalline phases of the monoclinic TiO 2 (B) and anatase by introducing small amount of H 3 PO 4 into sol solution as a crystal phase controller. The presence of TiO 2 (B) in the prepared mesoporous films expedited the lithium ion insertion/extraction reaction at the formal potential of 1.5 V vs. Li/Li + , and showed excellent long-term stability in electrochemical cycles.…”

Potential Applications for Solar Photocatalysis: From Environmental Remediation to Energy Conversion

“…Research in this field has been intense, given the growing worldwide demand for new energy sources (Kamat, 2007;Jacobson, 2009), either with focus on new materials and components or on cell assemblies for development of more efficient and environmentally friendly devices (Garcia et al, 2003;Prochazka et al, 2009;Zakeeruddin & Grätzel, 2009;Snaith, 2010). It is increasingly urgent the need to diversify energy matrices in order to rely on truly renewable energy sources, cleaner and environmentally friendly, if the goal is to build an ecologically sustainable society (Kamat, 2007;Herrero et al, 2011).…”

Mesoporous Building Blocks: Synthesis and Characterization of Mesoporous Silica Particles and Films

“…SBA-15 can e.g. be used as a template for anode or cathode materials for batteries [68][69][70]. Furthermore, it can also be used in solar cell applications, both as a template for incorporation of titania or cobalt nanoparticles [42,44,[71][72][73], and as a scattering layer for improving the cell efficiency [74].…”