Highly sensitive BTEX sensors based on hexagonal WO3 nanosheets

Abstract

Hexagonal WO3 (h-WO3) nanosheets (NSs), nanoparticles (NPs) and nanorods (NRs) were synthesized by a facile, low-cost and environmentally friendly hydrothermal and sol-hydrothermal methods. The structure and morphology of the products were characterized by several techniques, such as XRD, FESEM, TEM, and HRTEM. These results showed that the as-prepared WO3 were hexagonal nanosheets and the diameter was about 400 nm. Gas sensing tests of side-heating sensors indicated that the h-WO3 NSs had the superior selectivity and sensitivity for BTEX vapors (benzene, toluene, ethylbenzene, and p-xylol), which was 9 times more than h-WO3 NPs and NRs. At the optimal working temperature of 320 °C, the values of response based on the h-WO3 NSs sensor to 50 ppm BTEX vapors were 12.33, 27.73, 43.17, 36.27, respectively. The gas sensing mechanism of h-WO3 NSs was discussed in terms of DFT calculation, together with the XRD patterns. The results revealed that the adsorption energy of (100) facet to chemically adsorbed O2 molecules was more than that of (200) facet, which demonstrated strongly dependence on its exposed crystal facets to enhance gas sensing performance.