Operando XAS

Schematic setup of the Fluorescence XAS-cell. It allows to simultaneously measure the XAS and the change of sensors` resistance during exposure to target gases at elevated temperatures.

(In cooperation with KIT and ESRF)

In situ X-Ray Absorption spectroscopy on real MOX sensors under working conditions is the newest tool in our “operando toolbox”. This technique allows finding out the role and the impact of the so called noble metal “dopants” or “additives” like Pd, Pt and Au in metal oxide based gas sensors. They improve the sensitivity, selectivity and stability and decrease the operation temperature of the sensors. By using high energy synchrotron radiation the current oxidation state of the noble metals and possible changes during gaseous exposure can be monitored by XANES, operated in the fluorescence mode. Simultaneously the change in the resistance is measured. Furthermore, a detailed structural analysis of the surrounding (EXAFS) of the individual noble metal centers can be achieved by the use of special filters and mirrors. Consequently the role of noble metals and their structure under operating conditions can be identified by the application of operando XAS.




MOX gas sensors are studied by in situ X-Ray absorption spectroscopy under working conditions. Simultaneously to the structural studies (XANES spectra on the right), measurements of the sensing properties (resistance changes) are undertaken allowing for the determination of structure-function relationships.

Related References

  • Operando X-ray absorption spectroscopy studies on Pd-SnO2 based sensors, D. Koziej, M. Hübner, N. Barsan, U. Weimar, M. Sikora, J.D. Grunwaldt, Phys. Chem. Chem. Phys., 11-38, 2009, 8620–8625.

  • Operando fluorescent X-ray spectroscopy studies on the role of noble metal sensitizers in tin dioxide based gas sensors, D. Koziej, M. Hübner, N. Barsan, U. Weimar, J.D. Grunwaldt, Third international Congress on Operando Spectroscopy, 2009, Rostock-Warnemünde.

  • Shining the x-rays on the Pt:SnO2 based gas sensors in operando conditions, D. Koziej, M. Hübner, M. Bauer, N. Barsan, K. Kvashnina, M. D. Rossell, U. Weimar, J. Grunwaldt, MRS Fall Meeting, Boston, USA, Symposium TT, Paper Number 915776, 201, December, 2010.

  • The behavior of platinum in SnO2-based sensors under working conditions, M. Hübner, D. Koziej, M. Bauer, N. Barsan, K. Kvashnina, M.D. Rossell, U. Weimar, J.-D. Grunwaldt, Angew. Chem., in press.