Comparative study of the photodeposition of Pt, Au and Pd on pre-sulphated TiO2 for the photocatalytic decomposition of phenol

A comparative study of the photodeposition of Pt, Au and Pd under the same experimental conditions onto pre-sulphated and non-sulphated TiO2 was performed. Morphological and surface characterisation of the samples as well as photocatalytic activity for phenol photooxidation was studied. The influence of sulphate pre-treatment on the deposits size and dispersion onto the TiO 2 surface, and photodeposition yields with the different metals were also analysed. The photocatalytic activity of the doped materials was then investigated, observing that catalytic behaviour can be correlated to physical characteristics of the samples determined by (XRD) X-ray diffraction, (XPS) X-ray photoelectron spectroscopy, (XRF) X-ray fluorescence spectrometry and (TEM) transmission electron microscopy. Sulphate pre-treatment was found to influence both the level of dispersion and the size of metal clusters on the TiO2 surface. Sulphation and metallisation of samples was found to produce a synergistic enhancement in photoactivity for the degradation of phenol. The photoactivity of the catalysts with respect to the doped metal species was ordered Pt > Pd > Au.Ministerio de Ciencia e Innovación CTQ2008-05961-CO2-01Junta de Andalucía P06-FQM-140

Hydrothermal preparation of highly photoactive TiO2 nanoparticles

TiO2 nanoparticles have been prepared by amine assisted sol–gel precipitation of Ti4+ aqueous solutions and further hydrothermal treatment. The effect of different starting acidic solution (nitric, chlorhydric and acetic acids) as well as the addition of triethylamine (TEA) at different pH has been widely investigated. It has been stated that different amounts of TEA could have interesting effects upon hydrothermal treatment. Surface and morphological features significantly differ from TiO2 prepared using different synthetic route. In all cases, amine precipitated TiO2 obtained exhibit high conversion values for phenol photo-oxidation reaction, being in certain conditions higher than that exhibited by TiO2 Degussa P25. The precipitation of the acetic acidified solution leads to high surface area values and well crystallized anatase with small crystallite size. In addition, this set of catalysts show the cleanest surface after the hydrothermal treatment. The conjunction of these features would be the characteristic features responsible of the best photocatalytic activity observed

Synthesis and Deposition of Metal Nanoparticles by Gas Phase Condensation Process

In this work, a process which allows the production of nanoparticles in a vacuum environment is described. In the deposition machine, metal and inorganic composite particles can be generated through a plasma-based gas phase condensation process, using a modified gas flow sputter source. Besides, the gas phase condensation source is linked to a PECVD unit by a rotating sample holder, so that, by the combination of the two processes, the deposition of nanocomposite coatings consisting of metallic nanoparticles embedded in a thin film matrix material is also possible. The tool was used for the deposition of Pt and Ag nanoparticles onTiO2 thin films in order to improve its photocatalytic activity. Moreover, by embedding Ag nanoparticles in plasma polymers, layers for thin film plasmonic coatings could be fabricated

Plasma deposition of hydrophobic coatings on structured surfaces for condensation and heat transfer

The control of vapor condensation processes by suitably prepared surfaces is a prominent research area with important applications in the industry. For example, it is well known that the efficiency of condensation heat exchangers can be significantly increased when the vapor condenses to form droplets on the surface, instead of a closed film which does not wet the surface [1, 2]. In the present work, hydrophobic thin films are deposited via plasma CVD processes on metallic surfaces to investigate the condensation of water vapor on these surfaces. The drop-wise condensation on the coated surfaces is analyzed by optical microscopy and the effect on the heat transfer is measured by heat flux measurements. In order to show the potential of the deposition process for industrial applications and to investigate the effect of drop-wise condensation on heat transfer, copper (Cu) substrates were coated with a plasma polymer film using an organosilicon monomer (Hexamethyldisiloxane, HMDSO) as a precursor. In addition, the effect of surface roughness on the drop-wise condensation is presented because the static contact angle of water on hydrophobic surfaces depends strongly on surface topography