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“Systematic evaluation of thermal and mechanical stability of different commercial and synthetic photocatalysts in relation to their photocatalytic activity”. Ribbens S, Beyers E, Schellens K, Mertens M, Ke X, Bals S, Van Tendeloo G, Meynen V, Cool P, Microporous and mesoporous materials: zeolites, clays, carbons and related materials 156, 62 (2012). http://doi.org/10.1016/j.micromeso.2012.01.036
Abstract: The effect of thermal treatment and mechanical stress on the structural and photocatalytic properties of eight different (synthetic and commercial) photocatalysts has been thoroughly investigated. Different mesoporous Ti-based materials were prepared via surfactant based synthesis routes (e.g. Pluronic 123, CTMABr = Cetyltrimethylammonium bromide) or via template-free synthesis routes (e.g. trititanate nanotubes). Also, the stabilizing effect of the NaOH/NH4OH post-treatment on the templated mesoporous materials and their photocatalytic activity was investigated. Furthermore, the thermal and mechanical properties of commercially available titanium dioxides such as P25 Evonik® and Millenium PC500® were studied. The various photocatalysts were analyzed with N2-sorption, X-ray diffraction (XRD), high resolution transmission electron microscopy (HR-TEM), differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) to obtain information concerning the specific surface area, pore volume, crystal structure, morphology, phase transitions, etc. In general, results show that the NaOH post-treatment leads to an increased control of the crystallization process during calcination resulting in a higher thermal stability, but at the same time diminishes the photocatalytic activity. Mesoporous materials in which pre-synthesized nanoparticles are used as titania source have the best mechanical stability whereas the mechanical stability of the nanotubes is the most limited. At increased temperatures and pressures, the tested commercial titanium dioxides lose their superior photocatalytic activity caused by a decreased accessibility of the active sites. The observed changes in adsorption capacities and photocatalytic activities cannot be assigned to one single phenomenon. In this respect, it shows the need to define a general/standard method to compare different photocatalysts. Furthermore, it is shown that the photocatalytic properties do not necessarily deteriorate under thermal stress, but can be improved due to crystallization, even though the initial material is (partially) destroyed. It is shown that the usefulness of a specific type of photocatalyst strongly depends on the application and the temperature/pressure to which it needs to resist.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT); Laboratory of adsorption and catalysis (LADCA)
Impact Factor: 3.615
Times cited: 8
DOI: 10.1016/j.micromeso.2012.01.036
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“Combined TiO2/SiO2 mesoporous photocatalysts with location and phase controllable TiO2 nanoparticles”. Beyers E, Biermans E, Ribbens S, de Witte K, Mertens M, Meynen V, Bals S, Van Tendeloo G, Vansant EF, Cool P, Applied catalysis : B : environmental 88, 515 (2009). http://doi.org/10.1016/j.apcatb.2008.10.009
Abstract: Combined TiO2/SiO2 mesoporous materials were prepared by deposition of TiO2 nanoparticles synthesised via the acid-catalysed solgel method. In the first synthesis step a titania solution is prepared, by dissolving titaniumtetraisopropoxide in nitric acid. The influences of the initial titaniumtetraisopropoxide concentration and the temperature of dissolving on the final structural properties were investigated. In the second step of the synthesis, the titania nanoparticles were deposited on a silica support. Here, the influence of the temperature during deposition was studied. The depositions were carried out on two different mesoporous silica supports, SBA-15 and MCF, leading to substantial differences in the catalytic and structural properties. The samples were analysed with N2-sorption, X-ray diffraction (XRD), electron probe microanalysis (EPMA) and transmission electron microscopy (TEM) to obtain structural information, determining the amount of titania, the crystal phase and the location of the titania particles on the mesoporous material (inside or outside the mesoporous channels). The structural differences of the support strongly determine the location of the nanoparticles and the subsequent photocatalytic activity towards the degradation of rhodamine 6G in aqueous solution under UV irradiation.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Laboratory of adsorption and catalysis (LADCA)
Impact Factor: 9.446
Times cited: 69
DOI: 10.1016/j.apcatb.2008.10.009
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“Nanodesign of combined micro- and mesoporous materials for specific applications in adsorption and catalysis”. Meynen V, Busuioc AM, Beyers E, Cool P, Vansant EF, Bilba N, Mertens M, Lebedev O, Van Tendeloo G Nova, New York (2007).
Keywords: H3 Book chapter; Electron microscopy for materials research (EMAT); Laboratory of adsorption and catalysis (LADCA)
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“Quantification of crystalline and amorphous content in porous TiO2 samples from electron energy loss spectroscopy”. Bertoni G, Beyers E, Verbeeck J, Mertens M, Cool P, Vansant EF, Van Tendeloo G, Ultramicroscopy 106, 630 (2006). http://doi.org/10.1016/j.ultramic.2006.03.006
Abstract: We present an efficient method for the quantification of crystalline versus amorphous phase content in mesoporous materials, making use of electron energy loss spectroscopy. The method is based on fitting a superposition of core-loss edges using the maximum likelihood method with measured reference spectra. We apply the method to mesoporous TiO2 samples. We show that the absolute amount of the crystalline phase can be determined with an accuracy below 5%. This method takes also the amorphous phase into account, where standard X-ray diffraction is only quantitative for crystalline phases and not for amorphous phase. (c) 2006 Elsevier B.V.. All rights reserved.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Laboratory of adsorption and catalysis (LADCA)
Impact Factor: 2.843
Times cited: 83
DOI: 10.1016/j.ultramic.2006.03.006
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“Post-synthesis deposition of V-Zeolitic nanoparticles in SBA-15”. Meynen V, Beyers E, Cool P, Vansant EF, Mertens M, Weyten H, Lebedev OI, Van Tendeloo G, Chemical communications , 898 (2004). http://doi.org/10.1039/b400636d
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Laboratory of adsorption and catalysis (LADCA)
Impact Factor: 6.319
Times cited: 22
DOI: 10.1039/b400636d
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