Abstract
In this paper, we present a chemiresistive metal oxide (MOX) sensor for detection of hydrogen sulfide. Compared to the previous reports, the overall sensor performance was improved in multiple characteristics, including: sensitivity, selectivity, stability, activation time, response time, recovery time, and activation temperature. The superior sensor performance was attributed to the utilization of hybrid SnO2/TiO2 oxides as interactive catalytic layers deposited using a magnetron radio frequency (RF) sputtering technique. The unique advantage of the RF sputtering for sensor fabrication is the ability to create ultra-thin films with precise control of geometry, morphology and chemical composition of the product of synthesis. Chemiresistive films down to several nanometers can be fabricated as sensing elements. The RF sputtering technique was found to be very robust for bilayer and multilayer oxide structure fabrication. The geometry, morphology, chemical composition and electronic structure of interactive layers were evaluated in relation to their gas sensing performance, using scanning electron microscopy (SEM), X-ray diffraction technique (XRD), atomic force microscopy (AFM), Energy Dispersive X-ray Spectroscopy (EDAX), UV visible spectroscopy, and Kelvin probe measurements. A sensor based on multilayer SnO2/TiO2 catalytic layer with 10% vol. content of TiO2 demonstrated the best gas sensing performance in all characteristics. Based on the pattern relating material’s characteristics to gas sensing performance, the optimization strategy for hydrogen sulfide sensor fabrication was suggested.
Highlights
Hydrogen sulfide is a hazardous gas with strong odor
Multiple reports show that materials demonstrate the maximum of their catalytic activity in the nanoparticle form, Because of that, the energy of active sites on the surface is not enough to overcome the activation barrier of combustibles, ethanol and carbon dioxide, which provides a natural cut-off for all the catalytic reactions except for the H2 S decomposition and oxidation
Multiple reports show that materials demonstrate the maximum of their catalytic activity in the nanoparticle form, which is related to maximization of the surface area and the number of active sites
Summary
Hydrogen sulfide is a hazardous gas with strong odor. Lower concentrations of it can cause nausea, vomiting and eye irritation. SnO2 -based metal oxide structures with n-p and n-n heterojunction have attracted a great deal of interest as gas sensing materials [2,13,14,15,16,17,18,19]. It was suggested that the heterojunction resistance at the interface of two different oxides is more sensitive to the local gas environment than the contact resistance at the interface of two grains of the same nature This means that the content of the multilayer oxide structure can be optimized in order to achieve maximum sensing performance. One of the challenges for hydrogen sulfide detection by metal oxides is sulfur poisoning Many sensors lose their catalytic activity over time.
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