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To obtain nano-sized metal and metal salt crystallites with a narrow size distribution synthesis methods utilizing water in oil (w/o) microemulsions, i.e. reverse micelles, have been widely applied and reported in literature. In this study we show the effect of support addition at different stages of the reverse micelle based preparation of cobalt oxide on alumina model catalysts. All catalysts were characterized with X-ray powder diffraction and Raman spectroscopy indicating the presence of Co 3 O 4 on the Al 2 O 3 support. Studies of the reduction behaviour and X-ray photoelectron spectroscopy however revealed the presence of difficult to reduce cobalt aluminate species in the samples where the support was added during or shortly after the precipitation step in the synthesis process. It can therefore be assumed that if the alumina support is added to the reverse micelle solution unprecipitated Co 2? ions and partially dissolved Al 3? combine and form cobalt aluminates. In the preparations where the solid cobalt precipitates are recovered from the microemulsion and then supported on the carrier, no metal-aluminate formation could be observed. This study therefore gives important information how metal-support interaction can be affected during catalyst preparation using reverse micelles.

Flame spray pyrolysis (FSP) is a novel technique for the fabrication of nanostructured catalysts with farreaching options to control structure and composition even in cases where complex composites need to be prepared. In this study, we took advantage of this technique to synthesize highly dispersed pure and Pddoped iron oxide nanoparticles and investigated them as Fischer-Tropsch (FT) catalysts. By systematically varying the Pd content over a large range from 0.1 to 10 wt %, we were able to directly analyze the influence of the Pd content on activity and selectivity. In addition to catalytic measurements, the structure and composition of the particles were characterized before and after these measurements, using transmission electron microscopy, adsorption measurements, X-ray diffraction, and EXAFS. The comparison revealed on the one hand that small Pd clusters (diameter: 1-2 nm) evolve from initially homogeneously distributed Pd and on the other hand that the iron oxide transforms into iron carbides depending on the Pd content. The presence of Pd influences the particle size in the pristine samples (8-11 nm) resulting in specific surface areas that increase as the Pd content increases. However, after activation and reaction the specific surface areas become similar due to partial agglomeration and sintering. In a fixed bed FT reaction test, enhanced FT activity was observed with increasing Pd content while the selectivity shifts to longer chain hydrocarbons, mainly paraffins. Mechanistic implications regarding the role of Pd for the performance of the catalysts are discussed.

TiO 2 /benzoquinone hybrid films have been electrodeposited anodically from basic Ti(IV)-alkoxide solutions containing hydroquinone. The films were calcined at different temperatures between 350 and 550 °C and investigated in view of applications as photocatalyst and in dye-sensitized solar cells. Thermogravimetry analysis, differential thermo analysis, in situ X-ray diffraction, and transmission electron microscopy show the removal of the benzoquinone and starting crystallization of the TiO 2 between 350 and 400 °C, followed by a further increase in the crystallinity and particle size with increasing calcination temperature, while the specific surface area is decreased due to an increasing pore size as confirmed by Kr adsorption measurements. In dye-sensitized solar cells, the higher crystallinity leads to an improved performance mainly due to improved adsorption of sensitizer dyes up to calcination temperatures of 500 °C, while all films exhibit good electron collection properties as investigated by intensity-modulated photoelectrochemical techniques. The latter can be explained by the presence of conducting pathways provided by the benzoquinone for films calcined at lower temperature and by the presence of crystalline TiO 2 for films calcined at higher temperatures. A further increase of the calcination temperature to 550 °C leads to a decrease in efficiency due to a further decrease in the surface area. In contrast, the highest photocatalytic activity was found for a calcination temperature of 550 °C, indicating the importance of having highly crystalline and pure materials for photocatalytic applications.