Nanocomposites SnO₂/SiO₂ for CO Gas Sensors: Microstructure and Reactivity in the Interaction with the Gas Phase.

Dayana Gulevich,Valeriy Krivetskiy,Evgeny Gerasimov,Artem Marikutsa,Alexander Gaskov,Nikolay Khmelevsky,Marina Rumyantseva,Tatyana Shatalova

doi:10.3390/ma12071096

Dayana Gulevich, Valeriy Krivetskiy + Show 6 more

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https://doi.org/10.3390/ma12071096

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Abstract

Nanocomposites SnO2/SiO2 with a silicon content of [Si]/([Sn] + [Si]) = 3/86 mol.% were obtained by the hydrothermal method. The composition and microstructure of the samples were characterized by EDX, XRD, HRTEM and single-point Brunauer-Emmet-Teller (BET) methods. The surface sites were investigated using thermal analysis, FTIR and XPS. It is shown that the insertion of silicon dioxide up to the value of [Si]/([Sn] + [Si]) = 19 mol.% stabilizes the growth of SnO2 nanoparticles during high-temperature annealing, which makes it possible to obtain sensor materials operating stably at different temperature conditions. The sensor properties of SnO2 and SnO2/SiO2 nanocomposites were studied by in situ conductivity measurements in the presence of 10–200 ppm CO in dry and humid air in the temperature range of 150–400 °C. It was found that SnO2/SiO2 nanocomposites are more sensitive to CO in humid air as compared to pure SnO2, and the sample with silicon content [Si]/([Sn] + [Si]) = 13 mol.% is resistant to changes in relative air humidity (RH = 4%–65%) in the whole temperature range, which makes it a promising sensor material for detecting CO in real conditions. The results are discussed in terms of the changes in the composition of surface-active groups, which alters the reactivity of the obtained materials.

Highlights

Due to their physicochemical properties, wide-gap semiconductor metal oxides, such as SnO2, ZnO, WO3, In2 O3, are widely used as materials for resistive-type gas sensors
The composition of SnO2 /SiO2 samples determined by the energy dispersive X-ray spectroscopy (EDX) method is in good agreement with the Si/Sn ratio pre-assigned during the synthesis (Figure 2, Table 1)
When silicon is introduced into nanocomposites, the diffraction reflections of the tin dioxide phase are broadened, which indicates a decrease in the size of the SnO2 crystal grains

Summary

Introduction

Due to their physicochemical properties, wide-gap semiconductor metal oxides, such as SnO2 , ZnO, WO3 , In2 O3 , are widely used as materials for resistive-type gas sensors. The main requirements for the sensor material are selectivity, high sensitivity and thermal stability. The latter property is extremely important for the long-term operation of the sensor, as well as for measurements in a dynamic temperature mode (frequently used in e-nose devices), which allows an increase of the sensor signal due to more effective desorption of the products of the redox reaction from the surface of the semiconductor oxide [2,3,4,5].

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