Alexej Michailovski

High pressure in situ x-ray absorption spectroscopy cell for studying simultaneously the liquid phase and the solid/liquid interface

A high pressure in situ x-ray absorption spectroscopy cell with two different path lengths and path positions is presented for studying element-specifically both the liquid phase and the solid/liquid interface at pressures up to 250 bar and temperatures up to 220 °C. For this purpose, one x-ray path probes the bottom, while the other x-ray path penetrates through the middle of the in situ cell. The basic design of the cell resembles a 10 ml volume batch reactor, which is equipped with in- and outlet lines to dose compressed gases and liquids as well as a stirrer for good mixing. Due to the use of a polyetheretherketone inset it is also suitable for measurements under corrosive conditions. The characteristic features of the cell are illustrated using case studies from catalysis and solid state chemistry: (a) the ruthenium-catalyzed formylation of an amine in “supercritical” carbon dioxide in the presence of hydrogen; (b) the cycloaddition of carbon dioxide to propylene oxide in the presence of a solid Zn-b...

Solvothermal pathways towards transition metal oxides: Exploration and optimisation

A systematic solvothermal access towards nanoscale molybdenum and tungsten oxides has been established. Firstly, a versatile precursor material is selected that offers an interesting spectrum of reaction products. In the next step, a wide variety of straightforward ionic additives are screened to reveal and optimise all solvothermal pathways emerging from the precursor material. Finally, the appropriate precursor-additive combinations can be selected for further studies, such as nanorod design or the fabrication of novel materials.