Abstract
Nb‐loaded hexagonal WO3 nanorods with 0–1.0 wt% loading levels were successfully synthesized by a simple hydrothermal and impregnation process and characterized for SO2 sensing. Nb‐loaded WO3 sensing films were produced by spin coating on alumina substrate with interdigitated gold electrodes and annealed at 450°C for 3 h in air. Structural characterization by X‐ray diffraction, high‐resolution transmission electron microscopy, and Brunauer‐Emmett‐Teller analysis showed that spherical, oval, and rod‐like Nb nanoparticles with 5–15 nm mean diameter were uniformly dispersed on hexagonal WO3 nanorods with 50–250 nm diameter and 100 nm–5 µm length. It was found that the optimal Nb loading level of 0.5 wt% provides substantial enhancement of SO2 response but the response became deteriorated at lower and higher loading levels. The 0.50 wt% Nb‐loaded WO3 nanorod sensing film exhibits the best SO2 sensing performances with a high sensor response of ~10 and a short response time of ~6 seconds to 500 ppm of SO2 at a relatively low optimal operating temperature of 250°C. Therefore, Nb loading is an effective mean to improve the SO2 gas‐sensing performances of hydrothermally prepared WO3 nanorods.
Highlights
Sulfur dioxide (SO2) is a colorless toxic gas with burning smell that causes various respiratory and cardiovascular diseases as well as environmentally hazardous acid rain [1]
To synthesize unloaded WO3 nanorods, 2.215 g of Na2WO4⋅H2O and 0.7747 g of NaCl were dissolved in 100 mL of deionized (DI) water under constant stirring
WO3 nanorods prepared by hydrothermal and impregnation methods exhibit sharp X-ray diffraction (XRD) peaks whose locations are well matched to JCPDS 85-2459 [13], indicating polycrystalline structure of hexagonal WO3 phase with high crystallinity
Summary
Sulfur dioxide (SO2) is a colorless toxic gas with burning smell that causes various respiratory and cardiovascular diseases as well as environmentally hazardous acid rain [1]. The concentration of SO2 is still primarily determined by conventional techniques including gas chromatography or electrochemical detections, which are expensive, cumbersome, and impractical for onsite applications. Metal oxide semiconductor gas sensors are potential candidates for portable gas-sensing devices due to high sensitivity, good stability, low cost, small size, and simple electronic interface [1,2,3,4,5,6,7,8,9,10]. Only few metal oxide materials including WO3, SnO, and ZnO give significant response to SO2 and the reported response values are still limited [1].
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