Nanostructured of SnO 2 /NiO composite as a highly selective formaldehyde gas sensor
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School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, PR China National Engineering Research Center for Nanotechnology, Shanghai 200241, PR China 3 National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083, PR China a) Address all correspondence to this author. e-mail: [email protected] 2
Received: 28 June 2020; accepted: 17 August 2020
To detect low concentrations of formaldehyde selectively, the sensing properties of SnO2 nanostructured are enhanced by modifying with p-type semiconductor NiO. In this study, a nanostructured SnO2/NiO composite was prepared by a simple hydrothermal method. The X-ray photoelectron spectroscopy (XPS) peak in 532.4 eV proved that the existence of the SnO2/NiO composite structure increased the amount of adsorbed oxygen O− and O2− significantly. Gas-sensing tests showed that these mixed phases SnO2/NiO are highly promising for gas sensor applications, as the gas response for formaldehyde was significantly enhanced in gas response, selectivity at an operating temperature of 230 °C. The sensor fabricated by SnO2/NiO composite can detect as low as 1 ppm of formaldehyde at 230 °C, and the corresponding response is 1.57. The results of physicochemical properties tests of the samples show that the enhancement in sensitivity and selectivity is attributed to the oxygen vacancies and heterojunction between SnO2 and NiO. The SnO2/NiO composites can be applied to sensitive materials of formaldehyde sensors.
Introduction Formaldehyde is a kind of volatile and highly toxic gas, which is commonly found in interior decoration materials, and it is one of the main indoor pollution gases that are harmful to the human body [1]. The latest standard developed by WHO is that the body’s long-term exposure to formaldehyde should not exceed 0.08 ppm [2]. In the past few decades, formaldehyde detection methods have focused on gas chromatography [3], liquid chromatography, mass spectrometry, and fluorescence imaging. These methods have high sensitivity and selectivity, but are costly and require special handling of the sample, and take a long time. Therefore, developing a portable formaldehyde gas sensor with a low limit of detection, high response, low response time, and good stability has become an urgent problem to be solved. Metal-oxide semiconductors (MOSs) are widely used in the manufacture of gas sensors because they are easy to synthesis and have chemical stability [4]. Up to now, MOSs such as ZnO [5], In2O3 [6], SnO2 [7], WO3 [8], Co2O3 [9], NiO [10], and Fe2O3 [11] are widely used to manufacture gas sensors. To improve the sensitivity and selectivity of MOS, considerable
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efforts have been made through the control of morphology and size by different synthesis methods, such as hydrothermal [12], solvothermal [13], and electrospinning [14]. However, there are still many problems in achieving better sensitivity and higher selectivity by controlling the morpholog
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