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Berger M.E.M.,Chemical Reaction Engineering | Assenbaum D.,Chemical Reaction Engineering | Taccardi N.,Chemical Reaction Engineering | Spiecker E.,Center for Nanoanalysis and Electronic Microscopy | Wasserscheid P.,Chemical Reaction Engineering
Green Chemistry | Year: 2011

Exploitation of hydrogen as an energy carrier requires the development of systems for its storage and delivery. Formic acid has been proposed as valuable hydrogen carrier compound, due to its relatively high hydrogen content (53 g L-1), the latter being easily and cleanly released in catalytic reactions under mild conditions (HCOOH → H2 + CO2). Ionic liquids are interesting solvents for homogeneous catalyzed formic acid decomposition systems as their extremely low volatility avoids solvent contamination of the produced hydrogen stream. In this paper an outstandingly simple, robust and active catalyst system is presented, namely RuCl3 dissolved in 1-ethyl-2,3-dimethylimidazolium acetate (RuCl3/[EMMIM] [OAc]). This system proved to be fully recyclable over 10 times. Turnover frequencies (TOF) of 150 h-1 and 850 h-1 were obtained at 80 °C and 120 °C, respectively. © 2011 The Royal Society of Chemistry.


Distaso M.,Institute of Particle Technology | Mackovic M.,Center for Nanoanalysis and Electronic Microscopy | Spiecker E.,Center for Nanoanalysis and Electronic Microscopy | Peukert W.,Institute of Particle Technology
Chemistry - A European Journal | Year: 2014

By using ZnO as a model system, the formation of twinned nanostructures has been investigated under microwave irradiation, exploiting experimental conditions ranging from purely solvothermal when N,N-dimethylformamide was used, to purely hydrothermal when water was the solvent. A progressive increase in size, elongation and roughness of the surface was observed with increasing water content in the solvent mixture. Particular attention was paid to the reactivity of the ZnO surfaces towards dissolution. Our results show that the formation of twinned nanorods is a dynamic process and that the coupling interphase itself is highly reactive. Consequently, the twinned rods undergo a number of complex dissolution processes that are responsible for the appearance of a wide distribution of defects either on the surface or inside the structure. Poly(N-vinyl pyrrolidone) influences the photoluminescent properties of the as-synthesised materials and allows control of the ratio of the intensity of the UV and visible emission. Split at the seam cut! By increasing the water content of N,N-dimethylformamide reaction mixtures, the growth of anisotropic twinned ZnO nanostructures is achieved, characterised by the presence of a seam cut (see figure). Defect formation and surface dissolution occur, especially at the seam cut. The emission from defects is effectively quenched by using poly(vinyl pyrrolidone) during the synthesis. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Distaso M.,Institute of Particle Technology | MacKovic M.,Center for Nanoanalysis and Electronic Microscopy | Spiecker E.,Center for Nanoanalysis and Electronic Microscopy | Peukert W.,Institute of Particle Technology
Chemistry - A European Journal | Year: 2012

Let's become twins! Early stages of formation of twin ZnO nanorods under microwave irradiation have been studied. The coupling of facets with the same polarity was triggered by the rough surface and the defect-rich microstructure of the constituent ZnO building blocks. Oriented attachment was found to be the underlying mechanism of the twinning process (see scheme). © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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