Mesoporous titania directly doped with tungstophosphoric acid by urea-templated sol-gel synthesis as photodegradation catalyst

V. FUCHS, L. MENDEZ, M. BLANCO, L. PIZZIO

Moscu-San Petesburgo, Rusia

Conferencia; 2nd International IUPAC Conference on Green Chemistry; 2008

Titania (TiO2) is considered as one of the most suitable semiconductors to be used as photocatalyst due to its negligible toxicity, relatively high chemical stability and low cost. The photocatalytic activity of titania can be affected by several factors, such as the crystalline structure, the specific surface area, the particle size, the band gap (Eg) and the surface density of hydroxyl groups, among others. The hole-electron recombination and the low specific surface area are considered as the main factors leading to the low photocatalytic activity of TiO2. Mesoporous titania has been firstly prepared through a sol-gel process using a phosphate surfactant, and then different ionic or neutral surfactants have been employed. Recently, we started to use organic compounds of low cost as pore-forming agents, such as urea, in order to obtain mesoporous titania with high specific surface area. Keggin heteropolyacids have been added to TiO2 suspensions or anchored by chemical interactions on the support surface, with the purpose of reducing the charge recombination. In the present work, mesoporous titania directly doped with tungstophosphoric acid (TPA), obtained through reactions of the sol-gel type using urea as pore-forming agent, was synthesized. During the gelation step, alcoholic solutions of TPA were added, in order to obtain TPA contents of 0, 10, 20 and 30% w/w in the prepared material. Urea was leached with water and the obtained solids were thermally treated between 100 and 600 °C. Mesoporous solids with a mean pore diameter (Dp) higher than 3.1 nm were obtained. The specific surface area (SBET) decreased and Dp slightly increased with a higher TPA content. SBET2) is considered as one of the most suitable semiconductors to be used as photocatalyst due to its negligible toxicity, relatively high chemical stability and low cost. The photocatalytic activity of titania can be affected by several factors, such as the crystalline structure, the specific surface area, the particle size, the band gap (Eg) and the surface density of hydroxyl groups, among others. The hole-electron recombination and the low specific surface area are considered as the main factors leading to the low photocatalytic activity of TiO2. Mesoporous titania has been firstly prepared through a sol-gel process using a phosphate surfactant, and then different ionic or neutral surfactants have been employed. Recently, we started to use organic compounds of low cost as pore-forming agents, such as urea, in order to obtain mesoporous titania with high specific surface area. Keggin heteropolyacids have been added to TiO2 suspensions or anchored by chemical interactions on the support surface, with the purpose of reducing the charge recombination. In the present work, mesoporous titania directly doped with tungstophosphoric acid (TPA), obtained through reactions of the sol-gel type using urea as pore-forming agent, was synthesized. During the gelation step, alcoholic solutions of TPA were added, in order to obtain TPA contents of 0, 10, 20 and 30% w/w in the prepared material. Urea was leached with water and the obtained solids were thermally treated between 100 and 600 °C. Mesoporous solids with a mean pore diameter (Dp) higher than 3.1 nm were obtained. The specific surface area (SBET) decreased and Dp slightly increased with a higher TPA content. SBETband gap (Eg) and the surface density of hydroxyl groups, among others. The hole-electron recombination and the low specific surface area are considered as the main factors leading to the low photocatalytic activity of TiO2. Mesoporous titania has been firstly prepared through a sol-gel process using a phosphate surfactant, and then different ionic or neutral surfactants have been employed. Recently, we started to use organic compounds of low cost as pore-forming agents, such as urea, in order to obtain mesoporous titania with high specific surface area. Keggin heteropolyacids have been added to TiO2 suspensions or anchored by chemical interactions on the support surface, with the purpose of reducing the charge recombination. In the present work, mesoporous titania directly doped with tungstophosphoric acid (TPA), obtained through reactions of the sol-gel type using urea as pore-forming agent, was synthesized. During the gelation step, alcoholic solutions of TPA were added, in order to obtain TPA contents of 0, 10, 20 and 30% w/w in the prepared material. Urea was leached with water and the obtained solids were thermally treated between 100 and 600 °C. Mesoporous solids with a mean pore diameter (Dp) higher than 3.1 nm were obtained. The specific surface area (SBET) decreased and Dp slightly increased with a higher TPA content. SBET2. Mesoporous titania has been firstly prepared through a sol-gel process using a phosphate surfactant, and then different ionic or neutral surfactants have been employed. Recently, we started to use organic compounds of low cost as pore-forming agents, such as urea, in order to obtain mesoporous titania with high specific surface area. Keggin heteropolyacids have been added to TiO2 suspensions or anchored by chemical interactions on the support surface, with the purpose of reducing the charge recombination. In the present work, mesoporous titania directly doped with tungstophosphoric acid (TPA), obtained through reactions of the sol-gel type using urea as pore-forming agent, was synthesized. During the gelation step, alcoholic solutions of TPA were added, in order to obtain TPA contents of 0, 10, 20 and 30% w/w in the prepared material. Urea was leached with water and the obtained solids were thermally treated between 100 and 600 °C. Mesoporous solids with a mean pore diameter (Dp) higher than 3.1 nm were obtained. The specific surface area (SBET) decreased and Dp slightly increased with a higher TPA content. SBET2 suspensions or anchored by chemical interactions on the support surface, with the purpose of reducing the charge recombination. In the present work, mesoporous titania directly doped with tungstophosphoric acid (TPA), obtained through reactions of the sol-gel type using urea as pore-forming agent, was synthesized. During the gelation step, alcoholic solutions of TPA were added, in order to obtain TPA contents of 0, 10, 20 and 30% w/w in the prepared material. Urea was leached with water and the obtained solids were thermally treated between 100 and 600 °C. Mesoporous solids with a mean pore diameter (Dp) higher than 3.1 nm were obtained. The specific surface area (SBET) decreased and Dp slightly increased with a higher TPA content. SBETp) higher than 3.1 nm were obtained. The specific surface area (SBET) decreased and Dp slightly increased with a higher TPA content. SBETBET) decreased and Dp slightly increased with a higher TPA content. SBET also diminished with increasing calcination temperature, in a lower extent for the higher TPA