Design and validation of a novel operando spectroscopy reaction chamber for chemoresistive gas sensors

This work deals with the experimentation of a new ambient chamber for the use in diffuse reflectance Fourier infrared spectroscopy studies on chemoresistive gas sensors in operando condition. This system can support the investigation of gas–solid phase reactions at the sensor's surface during its operation, providing a reliable characterization tool that can be easily reproduced, implemented and adapted for several types of gas sensing devices. A deepened investigation was carried out: design of the chamber and the coupled acquisition system with temperature and humidity monitoring, 3D modelling, fluid dynamics study via residence time distribution analysis, and temperature gradient evaluation. Then, the system was validated in the case of a SnO2 sensor exposed to hydrogen gas flow. The new developed low void-volume gas sensing system is easy to machine, to use, to maintain, and it can be employed with solid-state gas sensors with an active area of 1 mm2 and operating temperatures up to 650 °C. In order to improve and facilitate the spectra acquisition, the system is equipped with precision staging and alignment, and it is fully compatible with Harrick Scientific's diffuse reflectance accessory.