Operando anomalous X-ray powder diffraction interleaved with X-ray absorption spectroscopy using a scanning 2D imaging detector on the XMaS beamline: design, implementation and performance.

Abstract

We present a method for achieving high-quality anomalous X-ray powder diffraction, interleaved with transmission X-ray absorption spectroscopy, using a flat-panel imaging detector scanned over a large angular range. Anomalous X-ray powder diffraction is a technique that enables the highlighting of specific elements within a crystal structure and pinpointing the nature of active (or inactive) sites involved in specific reactions in situ or in an operando manner. This approach enables the collection of a Q range that is not attainable using static flat-panel detectors in the absorption energy regimes used (8.94-17.5 keV). We consider the advantages and limitations of such an approach compared with alternative methods and describe in detail how it is achieved, along with the data processing and workflow required for an accurate restoration of conventional X-ray powder diffraction and anomalous X-ray powder diffraction data from sequentially acquired images. We demonstrate the applicability and capacity of this method for the in situ/operando restoration of the positions and atomic arrangement of copper atoms in the elevated-temperature aerobic activation of a copper-ion-exchanged zeolite, Cu-mazzite.