Abstract
Mesoporous titanium dioxide materials were prepared using a nanocasting technique involving silica SBA-15 as the hard-template. At an optimal loading of titanium precursor, the hexagonal periodic array of pores in SBA-15 was retained. The phases of titanium dioxide could be easily varied by the number of impregnation cycles and the nature of titanium alkoxide employed. Low number of impregnation cycles produced mixed phases of anatase and TiO2(B). The mesoporous TiO2 materials were tested for solar hydrogen production, and the material consisting of 98% anatase and 2% TiO2(B) exhibited the highest yield of hydrogen from the photocatalytic splitting of water. The periodicity of the pores was an important factor that influenced the photocatalytic activity. This study indicates that mixed phases of titania containing ordered array of pores can be prepared by using the nanocasting strategy.
Highlights
Titanium dioxide has been extensively studied because of its relative ease of synthesis, benign nature, and photocorrosion stability compared with other semiconductors, such as ZnO, etc. [1,2]
Many synthetic routes have been attempted for forming mesoporous titanium dioxide, such as room-temperature drying [9,10], low-temperature supercritical drying [11,12,13,14,15], high-temperature supercritical drying [16,17], hydrothermal [18,19,20], Evaporation-Induced Self-Assembly (EISA) [21,22,23], microwave [24,25], nanocasting employing soft template [26], and hard template [27,28,29,30,31,32,33,34,35,36,37,38,39,40]
The room-temperature drying of titanium dioxide gel to form a xerogel involves long evaporation time period with pores that are non-uniform in nature; this synthetic method is of little use in forming periodic array of pores [9,10]
Summary
Titanium dioxide has been extensively studied because of its relative ease of synthesis, benign nature, and photocorrosion stability compared with other semiconductors, such as ZnO, etc. [1,2]. The EISA synthesis has been performed to produce mixed phases of titanium dioxide; the materials lack periodic porous structure [42]. The formation of mixed phases of anatase, rutile, and TiO2(B) as function of loading and nature of titanium alkoxide precursor were carefully investigated using the hard-template synthetic method. The mixed phase titanium dioxide material with periodic hexagonal phase and having anatase (98%) and TiO2(B) (2%) without platinum co-catalyst exhibited the highest solar hydrogen activity. The results suggest mixed phases of titanium dioxide with periodic porous structure leads to the higher solar evolution compared with previous literature works in preparing mesoporous titanium dioxide having periodic network array of pores.
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