H2 detection mechanism in chemoresistive sensor based on low-cost synthesized WO3 nanorods

[摘要] Nanostructured WO3 represents a promising material for fast and reliable molecular hydrogen detection through chemo-resistive effect. Here, an extended experimental investigation of WO3-H-2 interaction is presented and modeled. A powder of WO3 nanorods (400 nm long, 50 nm large) is produced by hydrothermal technique and drop casted on Pt interdigitated electrode. H-2 sensing tests at different concentrations (2000-50,000 ppm) and temperatures (250-400 degrees C) are reported. Scanning Electron Microscopy (SEM), X-ray Diffraction analysis (XRD), and electrical measurements were performed. The response and recovery kinetics of H-2 sensing are carefully described by using a two-isotherms Langmuir model, and kinetics barriers for WO3-H-2 interaction are evaluated. Two microscopic processes lead to gas detection. A fast process (shorter than 4 s) is attributed to H-2 interaction with adsorbed oxygen at WO3 nanorods surface. A slow process (20-1000 s), with activation energy of 0.46 eV, is attributed to oxygen vacancy generation in WO3. H intercalation in WO3 is ruled out. The recovery of WO3 after H-2 exposure is also modeled. The chemo-resistive effect leading to H-2 sensing by WO3 is explained through the above processes, whose kinetic barriers have been quantified. These data open the route for the development of fast, sensitive, and low-temperature operating H-2 sensors based on WO3.

[发布日期] 2021-12-01

[关键词] Tungsten-trioxide;Hydrothermal;Nanostructures;Gas sensor;Hydrogen sensing