Conductometric H₂S Sensors Based on TiO₂ Nanoparticles

High-performance hydrogen sulfide (H₂S) sensors are mandatory for many industrial applications. However, the development of H₂S sensors still remains a challenge for researchers. In this work, we report the study of a TiO₂-based conductometric sensor for H₂S monitoring at low concentrations. TiO₂ samples were first synthesized using the sol-gel route, annealed at different temperatures (400 and 600 °C), and thoroughly characterized to evaluate their morphological and microstructural properties. Scanning electronic microscopy, Raman scattering, X-ray diffraction, and FTIR spectroscopy have demonstrated the formation of clusters of pure anatase in the TiO₂ phase. Increasing the calcination temperature to 600 °C enhanced TiO₂ crystallinity and particle size (from 11 nm to 51 nm), accompanied by the transition to the rutile phase and a slight decrease in band gap (3.31 eV for 400 °C to 3.26 eV for 600 °C). Sensing tests demonstrate that TiO₂ annealed at 400 °C displays good performances (sensor response Ra/Rg of ~3.3 at 2.5 ppm and fast response/recovery of 8 and 23 s, respectively) for the detection of H₂S at low concentrations in air.