Relationships between the structure of P-doped TiO2 xerogels and their photocatalytic properties

Conference (2011)

TiO2 heterogeneous photocatalysis has been the subject of numerous recent investigations as it is an attractive technique for the complete destruction of undesirable contaminants both in aqueous and ... [more ▼]

TiO2 heterogeneous photocatalysis has been the subject of numerous recent investigations as it is an attractive technique for the complete destruction of undesirable contaminants both in aqueous and gaseous phase by using solar or artificial light illumination. However, TiO2-based materials present a large band gap and therefore only a small fraction of solar light, in the UV region, can be utilized. Furthermore, anatase-TiO2 transforms to the rutile structure at temperatures relatively lower, which greatly reduces surface areas of the particles resulting in the decrease in photocatalytic ability of TiO2. To counter both disadvantages, several studies have been conducted by doping non-metallic elements, such as phosphor, into the Ti-O framework to form TiO2 solutions. In the present study, a sol-gel method is developed to synthesize P-doped TiO2 xerogels by a cogelation method based on the hydrolysis and the condensation of Ti(OC3H7)4 with functionalized P alkoxides: NH2-(CH2)2-NH-(CH2)2-P(O)-(OC2H5)2, or (C2H5O)2-P(O)-(CH2)7-CH3, in various alcohols. These xerogels are dried at 150°C under vacuum for 24 h, and calcined under air for 6 h at 350°C, 450°C, 550°C and 650°C. The resulting materials were characterized by TG-ATD, TEM, XRD, nitrogen adsorption-desorption isotherms, FT-IR and diffuse reflectance measurements in the UV/Vis region. It was found that the phosphor-doped species could significantly increase the surface area of the materials. Moreover, the phosphor-doping improved the thermal stability of titania and decreased the phase transformation of anatase to rutile. Diffuse reflectance measurements proved that the modification by phosphor shifted the absorption edge of titania to the visible region, making it an effective photocatalyst in visible light. This is shown by the degradation of p-nitrophenol under visible light irradiation. The excellent photocatalytic activity of P-doped TiO2 xerogels compared to pure TiO2 could be explained by its high surface area and small crystallite size. [less ▲]

Experimental procedure and statistical data treatment for the kinetic study of selective hydrodechlorination of 1,2-dichloroethane into ethylene over a Pd-Ag sol–gel catalyst

in Chemical Engineering Journal (2011), 173(3), 801-812

The kinetics of selective hydrodechlorination of 1,2-dichloroethane into ethylene over a Pd- Ag/SiO2 catalyst was studied using an a priori experimental design with five independent variables—temperature ... [more ▼]

The kinetics of selective hydrodechlorination of 1,2-dichloroethane into ethylene over a Pd- Ag/SiO2 catalyst was studied using an a priori experimental design with five independent variables—temperature and partial pressures of 1,2-dichloroethane, hydrogen, ethylene and hydrogen chloride. A Langmuir–Hinshelwood model including two types of active site and the 1,2-dichloroethane adsorption as the rate-determining step was found to fit correctly with experimental data, according to the analysis of variance and the analysis of pondered residuals. The study allowed for catalytic deactivation. The rigorous experimental and statistical approach followed to carry out such a kinetic study is explained in detail. [less ▲]

Improvement in the methylene blue adsorption capacity and photocatalytic activity of H2-reduced rutile-TiO2 caused by Ni(II)porphyrin preadsorption

in Applied Catalysis B : Environmental (2011), 106

H2-reduced rutile-TiO2 xerogel (Ti-700), obtained via the sol–gel process, was found to strongly adsorb the Ni(II)-5,10,15,20-tetrakis(4-carboxyphenyl)-porphyrin (NiTCPP) from a methanolic solution ... [more ▼]

H2-reduced rutile-TiO2 xerogel (Ti-700), obtained via the sol–gel process, was found to strongly adsorb the Ni(II)-5,10,15,20-tetrakis(4-carboxyphenyl)-porphyrin (NiTCPP) from a methanolic solution, despite its very low specific surface area (SBET ≈ 2 m2 g−1). UV/vis spectroscopy analysis showed that after calcination at 700 ◦C and reduction under H2 flow at 400 ◦C, the TiO2-xerogel increased its NiTCPP-adsorption capacity by surface area unit by up to 120 times. The effect of the porphyrin presence in the catalytic performances of TiO2-xerogels was studied through three kinetics models: (i) the pseudo-first-order kinetic model; (ii) the pseudo-second-order kinetic model, which are used to describe the adsorption rate based on the adsorption capacity of the catalysts; and (iii) the Langmuir–Hinshelwood kinetic model which is used to describe the photocatalytic degradation rate of methylene blue (MB). A significant improvement in the efficiency of Ti-700 was observed after the porphyrin-adsorption process (NiTCPP/Ti-700): MB-adsorption capacity at equilibrium and the apparent MB-photoconversion constant, kapp, of NiTCPP/Ti-700 were both up to 2 times higher than those observed for the Ti-700. [less ▲]

Development by sol-gel process of photocatalytic TiO2 thin films prepared by dip-coating

Poster (2010, July)

Activated-carbon-xerogel/TiO2-P25 composite photocatalysts with high activity for the degradation of p-nitrophenol

Poster (2010, July)

Chimie (3e partie)

Learning material (2010)

Unpredictable photocatalytic ability of H-2-reduced rutile-TiO2 xerogel in the degradation of dye-pollutants under UV and visible light irradiation

in Applied Catalysis B : Environmental (2010), 94

Study of the structure of P- and Si-doped TiO2 xerogels in relation with their formation mechanism

Poster (2009, January)

Ag-and SiO2-doped porous TiO2 with enhanced thermal stability

in Microporous & Mesoporous Materials (2009), 122

Synthesis of Ag/TiO2 hybrid photocatalysts by sol-gel process with new P-alkoxide functionalized ligands

Poster (2009)