Abstract
Methane detection is extremely difficult, especially at low temperatures, due to its high chemical stability. Here, WO3 nanosheets loaded with SnO2 nanoparticles with a particle size of about 2 nm were prepared by simple impregnation and subsequent calcination using SnO2 and WO3·H2O as precursors. The response of SnO2-loaded WO3 nanosheet composites to methane is about 1.4 times higher than that of pure WO3 at the low optimum operating temperature (90 °C). Satisfying repeatability and long-term stability are ensured. The dominant exposed (200) crystal plane of WO3 nanosheets has a good balance between easy oxygen chemisorption and high reactivity at the dangling bonds of W atoms, beneficial for gas-sensing properties. Moreover, the formation of a n–n type heterojunction at the SnO2-WO3 interface and additionally the increase of specific surface area and defect density via SnO2 loading enhance the response further. Therefore, the SnO2-WO3 composite is promising for the development of sensor devices to methane.
Highlights
The gas detection of methane is significantly important in coalmine production, usage of natural gas, atmospheric monitoring, etc
Our study showed that the SnO2-WO3 nanocomposite had higher sensitivity to methane than pure WO3 nanosheets and that the optimum operating temperature of both sensors was relatively low at 90 ◦C
All chemical reagents used in the experiments, including sodium tungstate (Na2WO4·2H2O, 99.5%), stannic chloride pentahydrate (SnCl4·5H2O, 99%), nitric acid (HNO3, 65%), polyethylene glycol 400 (PEG-400), sodium hydroxide (NaOH, 98%), aqueous ammonia (NH3·H2O 25–28%), and absolute ethanol were of analytical grade and as received without any further purification
Summary
The gas detection of methane is significantly important in coalmine production, usage of natural gas, atmospheric monitoring, etc. In order to reduce the operating temperature and improve the stability and sensitivity of different MOS gas sensors, methods such as noble metal/transition metal doping, heterojunction formation and unique surface morphology have been studied [8,9,10,11,12,13]. The SnO2-WO3 hybrid structure has received great attention because SnO2 and WO3 have different degrees of reaction to various redox gases, moderate resistivity, significant catalytic activity, high stability, low cost and unique gas-sensing characteristics [27,28,29,30,31,32,33,34]. Our study showed that the SnO2-WO3 nanocomposite had higher sensitivity to methane than pure WO3 nanosheets and that the optimum operating temperature of both sensors was relatively low at 90 ◦C. Gas-sensing properties were tested systematically and the gas-sensing mechanism was thoroughly discussed with the focus on the influence of the heterojunction and the observed dominant surface facet of the WO3 nanosheets
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