Abstract
The sensing characteristics of a yttria-stabilized zirconia (YSZ)-based sensor utilizing a NiO sensing-electrode (SE) towards toluene (C7H8) and interfering gases (C3H6, H2, CO, NO2 and C2H5OH) were evaluated with a view to selective C7H8 monitoring in indoor atmospheres. The fabricated YSZ-based sensor showed preferential responses toward 480 ppb C2H5OH, rather than the target 50 ppb C7H8 at an operational temperature of 450 °C under humid conditions (RH ≃ 32%). To overcome this limitation, the catalytic activity of Cr2O3, SnO2, Fe2O3 and NiO powders were evaluated for their selective ethanol oxidation ability. Among these oxides, SnO2 was found to selectively oxidize C2H5OH, thus improving C7H8 selectivity. An inline pre-catalytic cell loaded with SnO2 powder was installed upstream of the YSZ-based sensor utilizing NiO-SE, which enabled the following excellent abilities by selectively catalyzing common interfering gases; sensitive ppb level detection of C7H8 lower than the established Japanese Guideline value; low interferences from 50 ppb C3H6, 500 ppb H2, 100 ppb CO, 40 ppb NO2, as well as 480 ppb C2H5OH. These operational characteristics are all indicative that the developed sensor may be suitable for real-time C7H8 concentration monitoring in indoor environments.
Highlights
Since the wider awareness of the environmental and health concerns that volatile organic compounds (VOCs) pose, the development of high-performance VOCs sensors has been of great interest [1,2,3,4,5,6]
We reported that a mixed-potential type gas sensor, which consists of yttria-stabilized zirconia (YSZ) and a NiO sensing-electrode (SE), gave sensitive responses towards toluene, a typical and often representative VOC which exists in indoor atmospheres at ppb levels [14,15]
As seen in our previous paper [15], a YSZ-based sensor utilizing NiO-SE gave high responses towards several kinds of VOCs, such as toluene, m-xylene, benzene, ethylbenzene, styrene, and formaldehyde; with low negative effects caused by C3H6, H2, CO and NO2
Summary
Since the wider awareness of the environmental and health concerns that volatile organic compounds (VOCs) pose, the development of high-performance VOCs sensors has been of great interest [1,2,3,4,5,6] This is due to their disruptive nature in atmospheric chemistry as well as their hazardous effects on the human body. Low negative interferences of C3H6, H2, CO and NO2 were observed, suggesting a high possibility for a selective VOC sensor This sensor may be useful for real world VOC monitoring and indoor sensing applications, such as VOC detection in conjunction with heating, ventilation, and air conditioning (HVAC) control systems for the prevention of sick building syndrome. The sensing characteristics towards toluene and high concentrations of ethanol were evaluated for a NiO/YSZ-based sensor, aiming at the selective detection of ppb levels of toluene for indoor sensing applications
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