A versatile in situ spectroscopic cell for fluorescence/transmission EXAFS and X-ray diffraction of heterogeneous catalysts in gas and liquid phase

A new spectroscopic cell suitable for the analysis of heterogeneous catalysts by fluorescence EXAFS (extended X-ray absorption fine structure), transmission EXAFS and X-ray diffraction during in situ treatments and during catalysis is described. Both gas-phase and liquid-phase reactions can be investigated combined with on-line product analysis performed either by mass spectrometry or infrared spectroscopy. The set-up allows measurements from liquid-nitrogen temperature to 973 K. The catalysts are loaded preferentially as powders, but also as self-supporting wafers. The reaction cell was tested in various case studies demonstrating its flexibility and its wide applicability from model studies at liquid-nitrogen temperature to operando studies under realistic reaction conditions. Examples include structural studies during (i) the reduction of alumina-supported noble metal particles prepared by flame-spray pyrolysis and analysis of alloying in bimetallic noble metal particles (0.1% Pt-0.1% Pd/Al2O3, 0.1% Pt-0.1% Ru/Al2O3, 0.1% Pt-0.1% Rh/Al2O3, 0.1% Au-0.1% Pd/Al2O3), (ii) reactivation of aged 0.8% Pt-16% BaO-CeO2 NOx storage-reduction catalysts including the NOx storage/reduction cycle, and (iii) alcohol oxidation over gold catalysts (0.6% Au-20% CuO-CeO2).