Nitrogen dioxide sensing using tungsten oxide microspheres with hierarchical nanorod-assembled architectures by a complexing surfactant-mediated hydrothermal route

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2016-01, Vol.4 (4), p.1345-1352
• Main Authors: Shen, Yanbai, Wang, Wei, Chen, Xiangxiang, Zhang, Baoqing, Wei, Dezhou, Gao, Shuling, Cui, Baoyu
• Format: Article
• Language: English
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/c5ta08170j

WO 3 microspheres with hierarchical nanorod-assembled architectures were successfully synthesized by a complexing surfactant-mediated hydrothermal method in the presence of K 2 SO 4 and H 2 C 2 O 4 with a molar ratio of 1 : 1. Microstructural characterization by means of X-ray diffraction, scanning electron microscopy and transmission electron microscopy showed that WO 3 microspheres with diameters ranging from 3 to 5 μm were assembled by 90 nm diameter nanorods and had a single crystal hexagonal structure. The analysis results of the elemental composition and chemical state demonstrated that the obtained WO 3 microspheres were nearly stoichiometric. Based on the experimental results, a possible growth mechanism consisting of nucleation, Ostwald ripening, and self-assembly of WO 3 crystals was proposed. Gas sensing properties demonstrated that WO 3 microspheres exhibited not only a high response and excellent reversibility to NO 2 , but also a good linear relationship between the response and NO 2 concentration in the range of 1 to 10 ppm. The response and recovery times significantly decreased as the operating temperature increased gradually. The highest response of 790 to 20 ppm NO 2 was obtained at a relatively low operating temperature of 100 °C, which revealed that WO 3 microspheres were very promising for fabricating low-consumption chemical gas sensors. The electron depletion theory was used for explaining the gas sensing mechanism by the chemical adsorption and reaction of NO 2 gas molecules on the surface of WO 3 microspheres. WO 3 microspheres with hierarchical nanorod-assembled architectures were synthesized by a complexing surfactant-mediated hydrothermal method and showed high-performance NO 2 sensing properties.