(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.