A WO3 nanorod-Cr2O3 nanoparticle composite for selective gas sensing of 2-butanone

The hexagonal (h)-WO3-Cr2O3 nanocomposites with different W/Cr molar ratio of 4:1, 10:1 and 40:1 were prepared by a facile two-step hydrothermal method, and its gas sensing properties were investigated under optimum working temperature. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) were used to characterize the morphology, microstructure and crystallinity of the as-synthesized samples. The hexagonal WO3 nanorods show a better crystallinity than Cr2O3 nanoparticles. When the molar ratio of W/Cr is 10:1, the hexagonal WO3-Cr2O3 nanocomposite shows obvious selectivity toward 2-butanone at 205 °C compared with other typical reducing gases, and the response value to 100 ppm 2-butanone can reach 5.6. However, there is no selectivity toward 2-butanone when the Cr/W molar ratio is 1:4 and 1:40. Furthermore, hexagonal WO3-Cr2O3 nanocomposites have a short response and recovery time to 5 ppm 2-butanone, which is 10 s and 80 s, respectively. The measured results indicate that hexagonal WO3-Cr2O3 nanocomposite is a potential gas sensing material for monitoring volatile organic compounds (VOCs).