Titania mesopores

We also used the surfactant salts of phosphomolybdic acid (PMA) to react with tetrabutyl titanate instead of TEOS in order to obtain a containing-titania mesoporous phosphomolybdic acid. However, after the solvent extraction, the titania-modified samples exhibited a BET surface area of only 7 13 mVg, which indicated that there are no inner pores in it. We think that it may be due to the difficulty in the formation of the Mo-O-Ti bonds. 

P. Kluson, P. Kacer, T. Cajthaml and M. Kalaji, Preparation of titania mesoporous materials using... 

Lu L, Zhu Y, Li F, Zhuang W, Chan KY, Lu X Carbon titania mesoporous composite whisker as stable supercapacitor electrode material, / Mater Chem 20 7645—7651, 2010. 

The possibihty of obtaining nanopartides upon exposure to hard X-rays is not restricted to metallic nanopartides, in fact oxide nanopartides within a mesopo-rous ordered matrix have been also obtained. One example is ceriimi oxide nanopartides within a titania mesoporous ordered film to produce ceria NPs, the titania mesopores have been impregnated with a ceria precursor solution and then exposed to hard X-rays. Crystalline cerium oxide NPs with an average size of 4 nm have been grown within the mesopores, and different patterns with spatial control of the nanoparticle growth on the micrometer scale have been obtained [121]. 

The reduction of the catalyst precursor with sodium formate resulted in a lower Pd dispersion than the catalyst prepared by hydrogen reduction, the particle size is much larger in the former catalyst. The mesoporous carbon supported Pd catalysts are near to those of Pd on titania with respect to their enantiodifferentiating ability. Besides the metal dispersion, the availability of the Pd surface in the pores for the large modifier molecules seems to be the determining factor of the enantioselectivity. 

Preparation of chiral mesoporous materials has become a great interest for material scientists. Normally chiral property is introduced into chiral mesoporous material via an organic chiral templating component. But, by using a sonochemical method, Gabashvili et al. [36] have prepared mesoporous chiral titania using a chiral inorganic precursor and a non-chiral dodecylamine as a template. Size of the pores was 5.5 nm. 

Gabashvili A, Major DT, Perkas N, Gedanken A (2010) The sonochemical synthesis and characterization of mesoporous chiral titania using a chiral inorganic precursor. Ultrason Sonochem 17 605-609... 

Bare CuOx-supported nanostructures showed some activity in H 2 production from methanol-water mixture under UV-visible irradiation [180]. Ni is also used as a dopant, and small amounts (1 wt.%) of this element in mesoporous titania guarantee good activity in water-methanol mixtures under UV-visible light [181]. Indium-tantalum oxide Ni-doped materials also provided photocatalysts with promising efficiencies for direct water splitting [182]. TiOz nanotubes doped with Ir and Co nanopartides were effective for visible light water splitting even in the absence of... 

Ao, Y., Xu, J., Fu, D., and Yuan, C. (2009) Synthesis of C,N, S-tridoped mesoporous titania with enhanced visible light-induced photocatalytic activity. Microporous and Mesoporous Materials, 122 (1—3), 1-6. 

Liu, G., Chen, Z., Dong, C., Zhao, Y., H, F Lu, G.Q., and Cheng, H.M. (2006) Visible light photocatalyst iodine-doped mesoporous titania with a bicrystalline framework. Journal of Physical Chemistry B, 110 (42), 20823-20828. 

Shamaila, S., Sajjad, A.K.L., Chen, F., and Zhang, J. (2010) Study on highly visible light active Bi203 loaded ordered mesoporous titania. Applied Catalysis B Environmental, 94 (3—4), 272—280. 

Liu, R., Ren, Y., Shi, Y., Zhang, F., Zhang, L., Tu, B., and Zhao, D. (2007) Controlled synthesis of ordered mesoporous C—Ti02 nanocomposites with crystalline titania frameworks from organic-inorganic-amphiphilic coassembly. Chemistry of Materials, 20 (3), 1140-1146. 

Li, Y. and Kim, S.J. (2005) Synthesis and characterization of nano titania particles embedded in mesoporous silica with both high photocatalytic activity and adsorption capability. Journal of Physical Chemistry B, 109, 12309-12315. 

Titania films prepared by the methods described above are, however, just partially crystalline. Although WAXS patterns indicate formation of anatase crystals of ca. 10-12nm in size (Fig. 9.3a), the electron microscopy study demonstrates that the elongated crystals are actually embedded into an amorphous mesoporous matrix (Fig. 9.3c). The degree of crystallinity for such films usually does not exceed 60% attempts to increase it by calcination at higher temperatures cause uncontrolled crystal growth, which leads to collapse of mesoporos-ity and a drastic decrease in the surface area (Fig. 9.3d). 

The thermal stability of mesoporous frameworks substantially increases with an increase in the wall thickness and pore size, which can be varied even for the same template by changing the processing conditions. Ozin et al.55 developed a way to prepare crystalline titania films with a 2D-hexagonal architecture by replacement of ethanol in the Pluronic-containing precursor solution with more hydrophobic butanol-1. The latter promotes phase separation at low surfactant-to-titania ratios, resulting in thicker pore walls, which are more compatible with the crystal growth during subsequent calcination. 

Chen, L. Yao, B. Cao, Y. Fan, K. 2007. Synthesis of well-ordered mesoporous titania with tunable phase content and high photoactivity. J. Phys. Chem. C 111 11849-11853. 

Crepaldi, E. L. Soler-Illia, G Grosso, D. Cagnol, F. Ribot, F. Sanchez, C. 2003. Controlled formation of highly organized mesoporous titania thin films From... 

Lancelle-Beltran, E. Prene, P Boscher, C. Belleville, R Buvat, P Lambert, S. Guillet, F. Boissiere, C. Grosso, D. Sanchez, C. 2006. Nanostructured hybrid solar cells based on self-assembled mesoporous titania thin films. Chem. Mater. 18 6152-6156. 

Malfatti, L. Falcaro, P Amenitsch, H. Caramori, S. Argazzi, R. Bignozzi, C. A. Enzo, S. Maggini, M. Innocenzi, P. 2006. Mesostructured self-assembled titania films for photovoltaic applications. Microporous Mesoporous Mater. 88 304-311. 

Ngamsinlapasathian, S. Pavasupree, S. Suzuki, Y. Yoshikawa, S. 2006. Dye-sensitized solar cell made of mesoporous titania by surfactant-assisted templating method. Solar Energy Mater. Solar Cells 90 3187-3192. 

Although the mesoporous materials, such as Ti-MCM-41, have lower intrinsic epoxidation selectivity than TS-1 and Ti-beta, they must nevertheless be used as catalysts for reactions of large molecules typical in the fine chemicals industry. It is, therefore, interesting to elucidate how these ordered mesoporous materials compare with the earlier generation of amorphous titania-silica catalysts. Guidotti et al (189) recently compared Ti-MCM-41 with a series of amorphous titania-silica catalysts for the epoxidation of six terpene molecules of interest in the perfumery industry (Scheme 6). Anhydrous TBHP was used as the oxidant because the catalytic materials are unstable in water. The physical characteristics of these catalysts are compared in Table XII. 

Table 107 Properties and CO conversion rates as a function of temperature over Au catalysts in combination with mesoporous titania using a feed containing 4.494%CO and a steam partial pressure of 31.1 kPa. The catalyst volume was 0.5 cm3 and the space velocity was 4000 1C1 492...

Au/Ti02 Deposition precipitation 133 onto mesoporous titania 9.0 4.1 17 42 55... 

Au/Ti02 Deposition precipitation 134 onto mesoporous titania 8.0 6.2 43 80 86... 

This review will discuss the possibility to control and improve the reactivity of Titania by design of new tailored nano-architecture. Specifically, analyses quasi-ID Ti02 nanostructures, e.g. nanorods, nanowires and nanofibres, nanotubes and nanopillars. 2D Titania nanostructures, e.g. columnar-type films, ordered arrays of nanotubes or nano-rods/-wires, nanobowl array, nanomembranes (called also nanohole array) and nanosponge, and Ti-based ordered mesoporous matrices will be instead discussed in a consecutive review paper. 

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