References of "Poelman, Dirk"
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See detailSol-gel preparation and characterisation of SnO2 powders employed as catalyst for phenol photodegradation
Benhebal, Hadj; Chaib, Messaoud; Léonard, Angélique ULg et al

in Scientia Iranica (2013), 20(6), 1891-1898

Crystallized pure SnO2 powders were prepared by the sol-gel process and were used as photocatalyst for the degradation of phenol under UV light at pH 6.5 and a temperature of 20°C. The physical properties ... [more ▼]

Crystallized pure SnO2 powders were prepared by the sol-gel process and were used as photocatalyst for the degradation of phenol under UV light at pH 6.5 and a temperature of 20°C. The physical properties of photocatalyst were characterized by X-ray diffraction, Scanning Electron Microscopy, nitrogen adsorption-desorption and Ultraviolet-visible diffuse reflectance spectroscopy. The influences of different operating variables such as the pH, the photocatalyst loading, the initial concentration of phenol, were studied to improve the efficiency of phenol degradation. [less ▲]

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See detailDevelopment of Highly Active doped Titania Photocatalysts by Aqueous Sol-Gel Processing
Malengreaux, Charline ULg; Douven, Sigrid ULg; Poelman, Dirk et al

Poster (2012, December)

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See detailDevelopment of Highly Active doped Titania Photocatalysts by Aqueous Sol-Gel Processing
Malengreaux, Charline ULg; Douven, Sigrid ULg; Poelman, Dirk et al

Poster (2012, November)

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See detailSol-gel preparation of pure and doped TiO2 films for the photocatalytic oxidation of ethanol in air
Cimieri, Iolanda; Poelman, Hilde; Avci, Nursen et al

in Journal of Sol-Gel Science and Technology (2012), 63

Stable sols of TiO2 were synthesized by a non-aqueous sol-gel process using titanium (IV) isopropoxide (TTIP) as precursor. The microstructure, optical and morphological properties of the films obtained ... [more ▼]

Stable sols of TiO2 were synthesized by a non-aqueous sol-gel process using titanium (IV) isopropoxide (TTIP) as precursor. The microstructure, optical and morphological properties of the films obtained by spin-coating from the sol, and annealed at different temperatures, were investigated using SEM, TEM, diffuse reflectance spectroscopy (DRS) and ellipsometry. The crystalline structure of the films was characterized by X-ray diffraction and their photocatalytic activity was evaluated for the oxidation of ethanol in air. The influence of the calcination temperature, pre-heat treatment and the number of layers was studied. Simultaneous thermo-gravimetric and differential thermal analysis (TG/DTA) measurements were carried out to ascertain the thermal decomposition behavior of the precursors. In order to obtain a higher photoresponse in the visible region, a series of vanadium-, niobium- and tantalum-doped TiO2 catalysts was synthesized by the same sol-gel method. For V doping two different precursors, a vanadium alkoxide and V2O5, were used. The effect on the crystallization and photocatalytic activity of the doped TiO2 films was investigated. Furthermore, to identify the effective composition of the samples, they were characterized by X-ray photoelectron spectroscopy (XPS) and the surface area of the powders was measured by N2 adsorption. The 10wt.% doped catalysts exhibit high photocatalytic activity under visible light and among them the best performance was obtained for the sample containing Ta as dopant. The crystallite sizes are closely related to the photocatalytic activity. [less ▲]

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See detailOptimized deposition of TiO2 thin films produced by a non-aqueous sol-gel method and quantification of their photocatalytic activity
Malengreaux, Charline ULg; Timmermans, Adrien; Pirard, Sophie ULg et al

in Chemical Engineering Journal (2012), 195-196

TiO2 thin films have been produced by a dip-coating process using a non-aqueous sol-gel method. This study investigated the influence of the operating variables such as nature of the substrate, sol ... [more ▼]

TiO2 thin films have been produced by a dip-coating process using a non-aqueous sol-gel method. This study investigated the influence of the operating variables such as nature of the substrate, sol concentration, withdrawing speed of the dip-coater and number of layers on the physico-chemical properties of the films using XRD, GIXRD, UV-Vis spectroscopy, profilometry, spectroscopic ellipsometry and SEM. Photocatalytic activity of the films was evaluated by following the degradation of methylene blue under artificial UV light at 25°C. The performances of the catalysts were compared through the reaction rate constants determined using an apparent first-order kinetic model adjusted on the experimental data. This study showed that the photocatalytic activity and the reaction rate constant depend on the film thickness through the synthesis and dipping variable, with an optimum thickness of 80 nm being observed. An optimized transparent film exhibiting a high adhesion, a well crystallized TiO2-anatase phase, a good photocatalytic activity and a reaction rate constant k equal to 0.126 h-1 was obtained using a simple process. The specific photocatalytic activity of this film was higher to the one measured for TiO2 powders in previous works. [less ▲]

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See detailKinetic study of p-nitrophenol photodegradation with modified TiO2 xerogels
Tasseroul, Ludivine ULg; Pirard, Sophie ULg; Lambert, Stéphanie ULg et al

in Chemical Engineering Journal (2012), 191

TiO2 xerogels were sensitized in one step by the in situ introduction of nickel (II) tetra(4-carboxyphenyl)porphyrin (TCPPNi) into the TiO2 matrix during sol–gel synthesis. Crystalline photoactive phase ... [more ▼]

TiO2 xerogels were sensitized in one step by the in situ introduction of nickel (II) tetra(4-carboxyphenyl)porphyrin (TCPPNi) into the TiO2 matrix during sol–gel synthesis. Crystalline photoactive phase TiO2-anatase was obtained without high thermal treatments and was determined by X-ray diffraction. The presence of TCPPNi in TiO2 xerogels was established by DR-UV/Vis and FT-IR spectroscopy. The introduction of porphyrin led to a diminution of the specific surface area of TiO2 xerogels, and this diminution was analyzed by nitrogen adsorption–desorption. The particle size was estimated by SEM. The xerogel surface charge state, which influences the interactions between pollutant and TiO2, was determined by measurement of the point of zero charge. The photoactivity of xerogels was evaluated for p-nitrophenol degradation in aqueous medium at 20 ◦C. Results showed that porphyrin doped TiO2 degraded more than 40% of the p-nitrophenol whereas non doped TiO2 xerogel degraded only 10% of the compound. Moreover, porphyrin was found to improve the photoactivity of TiO2 xerogels in a similar way to UV-A pretreatment. A kinetic study of p-nitrophenol degradation was then performed. Results showed that one type of active site corresponding to the hole of electron–hole pairs was created at the TiO2 surface by light and that the rate determining step was the reaction between the adsorbed p-nitrophenol molecule and the adsorbed OH• radical. The apparent activation energy was found to be equal to 12 kJ mol−1. [less ▲]

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See detailMechanisms of photocatalysis in TiO2 thin films for air purification
Poelman, Dirk; Heinrichs, Benoît ULg

Report (2012)

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See detailOptimized deposition of photocatalytic TiO2 thin films produced by a non-aqueous sol-gel method
Malengreaux, Charline ULg; Timmermans, Adrien; Pirard, Sophie ULg et al

Poster (2011, November)

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See detailOptimized deposition of photocatalytic TiO2 thin films produced by a non-aqueous sol-gel method
Malengreaux, Charline ULg; Timmermans, Adrien; Pirard, Sophie ULg et al

Poster (2011, September)

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See detailAqueous and non-aqueous sol-gel preparation of TiO2 films for the photocatalytic oxidation of ethanol in air
Cimieri, Iolanda; Poelman, Hilde; Lambert, Stéphanie ULg et al

Poster (2011)

One of the most versatile methods to prepare TiO2 fine powders and films is the sol-gel technique. It offers many advantages, among which the possibility to control the stoichiometry, work in mild and ... [more ▼]

One of the most versatile methods to prepare TiO2 fine powders and films is the sol-gel technique. It offers many advantages, among which the possibility to control the stoichiometry, work in mild and ambient atmospheric conditions and achieve high purity and homogeneity of the final product. Stable TiO2 sols were synthesized by an aqueous sol-gel process using titanium tetraisopropoxide (TTIP) as precursor and nitric acid in water as hydrolyzing agent. The aim of the present study was to investigate the influence of different solvents and different amounts of HNO3 on the photocatalytic activity of TiO2 in the breakdown of ethanol (EtOH) as VOC molecule under UV and visible light. In particular, ethanol, isopropanol and butanol were used as solvents and two different molar ratios of HNO3 with respect to TTIP (0.25 and 0.5 respectively) were used. Their effect was investigated with regard to the photocatalytic properties of the films obtained by spin coating on sodium free glass [1] and heat treated at 450°C in air. The microstructure, optical and morphological properties of the films were investigated using SEM, UV-Vis spectroscopy and ellipsometry. The nature of the crystalline phases was ascertained by X-ray diffraction and the surface area of the powders was measured by N2 adsorption. The porous TiO2 films obtained show quite good photocatalytic activity for the degradation of EtOH compared to titania films prepared using P25 Degussa as shown in Fig. 1. Further the photocatalytic properties of the thin films obtained by aqueous sol-gel method were compared with the activity of films prepared using the same titanium precursor by a non-aqueous sol-gel process, in which the hydrolysis is initialized by esterification reaction between acetic acid and alcohol. (Fig.1. EtOH degradation for P25 (green), non aqueous sol (purple) and aqueous sols prepared using ethanol as solvent and HNO3 in molar ratios 0.25(blue) and 0.50(red)) [1] H. Tomaszewski, K. Eufinger, H. Poelman, D. Poelman, R. De Gryse, P.F.Smet, G.B. Marin, Int. J. Photoenergy 8, 1 (2007) [less ▲]

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See detailUnpredictable photocatalytic ability of H2-reduced rutile-TiO2 xerogel in the degradation of dye-pollutants under UV and visible light irradiation
Páez Martínez, Carlos ULg; Lambert, Stéphanie ULg; Poelman, Dirk et al

Poster (2011)

Photocatalytic degradation of organic and inorganic pollutants on the TiO2 semiconductor has been extensively studied as a way to solve environmental problems relating to wastewater and polluted air ... [more ▼]

Photocatalytic degradation of organic and inorganic pollutants on the TiO2 semiconductor has been extensively studied as a way to solve environmental problems relating to wastewater and polluted air. Anatase and rutile are the most commonly used crystalline structures of TiO2, with anatase showing a higher photocatalytic activity attributed to its higher specific surface area and its favourable band gap energy (Eg). However, its high band gap (Eg = 3.2 eV) implies the use of UV light (lambda ≤ 380 nm) to inject electrons into the conduction band (TiO2(e-CB)) and to leave holes in the valence band (TiO2(h+VB)). Although the low band gap energy of rutile-TiO2 (Eg = 3.02 eV) allows rutile to potentially absorb more solar energy than anatase, the anatase-to-rutile phase transition leads to the collapse of the TiO2 specific surface area, which may result in a decrease in the photocatalytic activity of rutile. Low specific surface area and therefore poor absorption properties lead to strong limitations in exploring the photo-efficiency of rutile. Nevertheless, rutile has been proved to be comparable to anatase in its photoelectrochemical properties when used in dye-sensitized solar cells. In the present study, a new process for the reduction of rutile-TiO2 xerogel under hydrogen flow was developed to enhance the photocatalytic activity of TiO2 materials synthesized by the sol-gel process. So a series of H2-reduced TiO2 xerogels of low specific surface area was prepared by hydrolysis and condensation of tetraisopropoxy titanium(IV) in 2-methoxyethanol. The gels were dried under vacuum, calcined in air at different temperatures (400°C, 500°C and 700°C) and finally reduced in H2 at 400 °C. The materials were characterized by X-ray diffraction, transmission electron microscopy (TEM), FT-IR spectroscopy and UV/Visible diffuse reflectance spectroscopy. The texture was determined by nitrogen adsorption-desorption measurements. The effects of the calcination/reduction treatments on the adsorption of methylene blue (MB) in aqueous solution and on the photocatalytic degradation of MB and crystal violet (CV) under UV and visible light irradiation were also evaluated. Results showed predictable modifications in the physico-chemical properties caused by the annealing of TiO2 xerogel at high calcination temperature (700 °C), such as a total anatase-to-rutile phase transition and a considerable loss of specific surface area from 260 to 2 m2 g-1. However, the higher degree of reduction exhibited by the rutile-TiO2 lattice led to unpredictable photocatalytic activity for the dye conversion under UV and visible light irradiation: the loss of specific surface area of the rutile-TiO2 sample was compensated by the increase in the affinity of this sample for the dye. Under UV light irradiation, the rutile-TiO2 xerogel obtained after a calcination at 700 °C showed a similar level of photoactivity as the one obtained with anatase-TiO2 xerogels obtained by calcination at 400 °C and 500 °C. Under visible light, unlike anatase-TiO2 xerogels, the rutile-TiO2 xerogel showed a higher dye photoconversion rate per external surface area (40 times higher) than the commercial TiO2 Degussa P25. [less ▲]

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See detailImprovement in the methylene blue adsorption capacity and photocatalytic activity of H2-reduced rutile-TiO2 caused by Ni(II)porphyrin preadsorption
Páez Martínez, Carlos ULg; Lambert, Stéphanie ULg; Poelman, Dirk et al

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 ▲]

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See detailAg-and SiO2-doped porous TiO2 with enhanced thermal stability
Braconnier, Benoît ULg; Páez Martínez, Carlos ULg; Lambert, Stéphanie ULg et al

in Microporous and Mesoporous Materials (2009), 122

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