Monitoring of fast transformations in solid state chemistry and heterogeneous catalysis by QEXAFS in the second scale

Abstract

The present paper points out the possibility of investigating solid-solid transformations using time dependent x-ray absorption spectroscopy (QEXAFS) on a second scale. For this purpose, new crystal driving mechanics were developed which enable the measurement of complete x-ray absorption spectra extending over up to 2000 eV with repetition frequencies of up to 40 Hz and the possibility of monitoring a reference sample simultaneously. This permits to detect even very small changes of the edge position—and thus the chemical valency of the species of interest—with a high accuracy. The application of the new set up is demonstrated for the in situ analysis of the thermal decomposition of Co-oxalate-hydrate in different gas atmospheres. The results prove that the details of the decomposition process and the formed reaction products depend sensitively on the composition of the gas atmosphere.