Chemoresistive gas-sensing properties of highly dispersed Nb2O5 obtained by programmable precipitation

Nb2O5 powder obtained by programmable precipitation was used to form a thick gas-sensing film as part of a chemoresistive gas sensor, by screen-printing. The coating of orthorhombic Nb2O5 consisted of nanoparticles with a size of 41.0 ± 2.5 nm. XPS revealed Nb5+, Nb4+ and Nb2+ as well as oxygen vacancies in the crystal structure of niobium oxide. As a result of studying the chemoresistive gas-sensing properties of Nb2O5, it has been shown that among the analysed gases (H2, CO, NH3, H2S and О2), the greatest sensitivity was observed for oxygen and hydrogen sulphide. Nanocrystalline niobium oxide showed a high and reproducible response to 0.02–20% О2 (S1 = 1.1–19.0) at a very low detection temperature of 200 °C for oxygen sensors. At an operating detection temperature of 250 °C, a high and reproducible response to low concentrations of hydrogen sulphide of 4–100 ppm (S2 = 1.2–6.6) was detected for Nb2O5. The influence of humidity on the received signals when detecting oxygen and hydrogen sulphide was studied in detail: there was a decrease in the resistance and the response value at 95% humidity in the medium of both gases. However, unlike the process of detecting H2S (when the response of S2 was almost lost), when determining oxygen, the response of S1 was reduced by a factor of two only, which suggests the possibility of determining the content of O2 in high humidity conditions.