In situ cell for grazing-incidence x-ray diffraction on thin films in thermal catalysis

A cell for synchrotron-based grazing-incidence x-ray diffraction at ambient pressures and moderate temperatures in a controlled gas atmosphere is presented. The cell is suited for the in situ study of thin film samples under catalytically relevant conditions. To some extent, in addition to diffraction, the cell can be simultaneously applied for x-ray reflectometry and fluorescence studies. Different domes enclosing the sample have been studied and selected to ensure minimum contribution to the diffraction patterns. The applicability of the cell is demonstrated using synchrotron radiation by monitoring structural changes of a 3 nm Pd thin film upon interaction with gas-phase hydrogen and during acetylene semihydrogenation at 150 °C. The cell allows investigation of very thin films under catalytically relevant conditions.