An in situ atmospheric-pressure dielectric barrier discharge setup for time-resolved synchrotron characterisation of cerium metal-organic frameworks

In situ investigation of plasma-material interactions are essential for understanding material stability and transformation mechanisms under non-thermal plasma (NTP) conditions. Nevertheless, such studies remain challenging due to the limited availability of plasma reactors compatible with synchrotron-based structural and spectroscopic techniques. Here, we present the design, construction, and characterisation of a dedicated in situ atmospheric-pressure dielectric barrier discharge (DBD) reactor enabling quasi-simultaneous X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) during plasma exposure.The compact reactor integrates a quartz discharge tube, an exchangeable powder sample holder, a controlled gas-flow system, and aligned driven and grounded electrodes. The geometry ensures that the reactive gas stream passes directly through the sample while maintaining optical and X-ray access. Stable plasma operation is achieved at 20.8 kHz and peak-to-peak voltages up to 14 kV with various gas mixtures. Electrical diagnostics based on current-voltage measurements and Lissajous analysis quantify discharge power, transferred charge, and effective plasma capacitance, confirming reproducible and tunable plasma conditions. Optical imaging and thermocouple measurements further validate discharge position in relation to the sample and provide temperature control up to 200 °C. Compatibility with synchrotron radiation investigation is demonstrated at a dedicated beamtime at ESRF (BM23) through time-resolved transmission XAS and XRD measurements. As a proof of concept, cerium-based metal–organic frameworks, Ce-CAU-41 and -44, were investigated, illustrating the capability of the setup to track plasma-induced structural and chemical changes in real time. The developed reactor provides a robust and flexible tool for in situ synchrotron studies of plasma-driven processes and enables mechanistic investigations of material transformations under atmospheric-pressure plasma conditions.