Abstract
In this work, flower-like ZnO nanorods (NRs) were successfully prepared using microwave-assisted techniques at a low temperature. The synthesized NRs exhibited a smooth surface and good crystal structure phase of ZnO. The sharp peak of the XRD and Raman spectrum confirmed the high crystallinity of these ZnO NRs with a pure wurtzite structure. The nanorods were ~2 μm in length and ~150 nm in diameter, respectively. The electron diffraction pattern confirmed that the single crystal ZnO nanorods aligned along the [001] plane. The NRs were applied to fabricate a gas sensor for reducing gases such as CH4, CO, and H2. The sensor showed a good performance and sensitivity toward the target gases. However, its response toward CH4 and CO was higher compared to H2 gas. Although the operating temperature was varied from room temperature (RT) up to 350°C, the sensor did not show a response toward any of the target gases in the range of RT-150°C, but dramatic enhancement of the sensor response was observed at 200°C, and up to higher temperatures. This behavior was ascribed to the activity of the smooth surface and the reactivity of surface oxygen species with the targeted gases. The sensor response was measured at various gas concentrations, where the calibration curve was shown. The gas sensing mechanism was described in terms of the reaction of the gases with the transformed oxygen species on the surface of the oxides.
Highlights
Due to their optical and physical properties, ZnO nanostructures have become a suitable material to use in different environmental monitoring applications (Livage, 1981; Roy et al, 2011; Spencer, 2012; Brookes et al, 2014; Kumar et al, 2015; Chen et al, 2019; Zada et al, 2019, 2020; Qi et al, 2020a,b)
ZnO NRs supported by the complex surfactant showed excellent ethanol sensing properties at an optimal operating temperature of 300 ◦C, which could be attributed to their large surface to volume ratio, and a high number of surface defects due to oxygen vacancies (Zhao et al, 2019)
The morphology and structure were studied by XRD, FESEM, and Raman spectroscopy
Summary
Due to their optical and physical properties, ZnO nanostructures have become a suitable material to use in different environmental monitoring applications (Livage, 1981; Roy et al, 2011; Spencer, 2012; Brookes et al, 2014; Kumar et al, 2015; Chen et al, 2019; Zada et al, 2019, 2020; Qi et al, 2020a,b) One of these applications that have attracted the interests of scientific communities is gas– sensing applications that require some specific characteristics such as high surface-to-volume ratio and good chemical and thermal stability (Vomiero et al, 2007; Guo et al, 2012; Pan et al, 2013; Bai et al, 2014; Hosseini et al, 2015; Jin et al, 2015; Mascini et al, 2018; Jingxuan et al, 2020). The shape control of Pd NCs with close {111} packing effects remarkably enhances the catalytic activity and capacity for H2 adsorption compared to that of {100}
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