SNO2/ZNO POWDERS AND THIN FILMS FOR H2 AND NO2 MONITORING IN WATER TREATMENT PLANTS

Water treatment plants often use technologies associated with the emission of various gases. These can be anaerobic digestion processes, various methods of converting waste from wastewater treatment plants into valuable resources such as biogas. Increasingly, in order to comply with the principles of a circular economy, in to water purification additional processes such as electrolysis are carried out to obtain green hydrogen. Sometimes the preparation of drinking water itself requires a clean gas environment. Metal oxide semiconductor (MOS) gas sensors are used to monitor air at water objects and treatment plants. The work is devoted to studying the properties of SnO2/ZnO powders and thin films with different molar ratios for monitoring hydrogen and nitrogen (IV) oxide. To characterize SnO2/ZnO powders, X-ray phase and X-ray structural analyses were performed, diffuse reflection spectra were obtained in the UV-visible range, the band gap energy was calculated, and porosity and specific surface area were determined. Powder diffraction patterns were obtained for which the crystallite size was determined depending on the SnO2/ZnO molar ratio. The band gap values range from 3.0 to 3.49 eV depending on the crystallite size. The most developed porous structure is 63.2 m2/g in a powder with 60% SnO2, in which the average pore size is about 8.5 nm.. To study the response of the synthesized thin films to hydrogen and nitrogen (IV) oxide, impedance spectroscopy was performed in a closed system without access to moisture at room temperature under the influence of ultraviolet radiation. The highest response value to NO2 is observed for the film with a molar ratio of SnO2 to ZnO as 4 to 1 (80%/20%), which is at the level of 2.12. The highest response to hydrogen is 2.42 and corresponds to a sensitive material consisting of 100% SnO2.