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Hydrogen sulfide (H2S) and sulfur dioxide (SO2) are two typical decomposition byproducts of sulfur hexafluoride (SF6), commonly used as an insulating medium in electrical equipment; for instance, in gas circuit breakers and gas insulated switchgears. In our work, fiber-like p-CuO/n-ZnO heterojunction gas sensing materials were successfully prepared via the electrospinning method to detect the SF6 decomposition byproducts, H2S and SO2 gases. The sensing results demonstrated that p-CuO/n-ZnO nanofiber sensors have good sensing performance with respect to H2S and SO2. It is noteworthy that this fiber-like p-CuO/n-ZnO heterojunction sensor exhibits higher and faster response–recovery time to H2S and SO2. The enhanced sensor performances can probably be attributed to the sulfuration–desulfuration reaction between H2S and the sensing materials. Moreover, the gas sensor exhibited a high response to the low exposure of H2S and SO2 gas (below 5 ppm). Towards the end of the paper, the gas sensing mechanism of the prepared p-CuO/n-ZnO heterojunction sensors to SO2 and H2S is discussed carefully. Calculations based on first principles were carried out for Cu/ZnO to construct adsorption models for the adsorption of SO2 and H2S gas molecules. Information on adsorption energy, density of states, energy gap values and charge density were calculated and compared to explain the gas-sensitive mechanism of ZnO on SO2 and H2S gases. [ABSTRACT FROM AUTHOR]

In this study, we reported a successful synthesis of a nanocomposite based on SnO 2 nanoneedles anchored to NiO microsphere by a simple two-step hydrothermal route. The results show that the SnO 2 /NiO nanocomposite-based sensor exhibits more prominent performances than the pristine NiO microsphere to NO 2 such as larger responses and more outstanding repeatability. The improved properties are mainly attributed to the p-n heterojunctions formed at the SnO 2 -NiO interface, leading to the change of potential barrier height and the enlargement of the depletion layer. Besides, the novel and unique nanostructure provides large and effective areas for the surface reaction. In addition, a plausible growth mechanism and the enhanced sensing mechanism were proposed to further discuss the special nanostructure which will benefit the exploration of high-performance sensors.

Hydrogen sulfide (H 2 S) is an important decomposition component of sulfur hexafluoride (SF 6 ), which has been extensively used in gas-insulated switchgear (GIS) power equipment as insulating and arc-quenching medium. In this work, electrospun ZnO-SnO 2 composite nanofibers as a promising sensing material for SF 6 decomposition component H 2 S were proposed and prepared. The crystal structure and morphology of the electrospun ZnO-SnO 2 samples were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively. The composition of the sensitive materials was analyzed by energy dispersive X-ray spectrometers (EDS) and X-ray photoelectron spectroscopy (XPS). Side heated sensors were fabricated with the electrospun ZnO-SnO 2 nanofibers and the gas sensing behaviors to H 2 S gas were systematically investigated. The proposed ZnO-SnO 2 composite nanofibers sensor showed lower optimal operating temperature, enhanced sensing response, quick response/recovery time and good long-term stability against H 2 S. The measured optimal operating temperature of the ZnO-SnO 2 nanofibers sensor to 50 ppm H 2 S gas was about 250°C with a response of 66.23, which was 6 times larger than pure SnO 2 nanofibers sensor. The detection limit of the fabricated ZnO-SnO 2 nanofibers sensor toward H 2 S gas can be as low as 0.5 ppm. Finally, a plausible sensing mechanism for the proposed ZnO-SnO 2 composite nanofibers sensor to H 2 S was also discussed.

Tin oxide SnO 2 -based gas sensors have been widely used for detecting typical fault characteristic gases extracted from power transformer oil, namely, H 2 , CO, CO 2 , CH 4 , C 2 H 2 , C 2 H 4 , and C 2 H 6 , due to the remarkable advantages of high sensitivity, fast response, long-term stability, and so on. Herein, we present an overview of the recent significant improvement in fabrication and application of high performance SnO 2 -based sensors for detecting these fault characteristic gases. Promising materials for the sensitive and selective detection of each kind of fault characteristic gas have been identified. Meanwhile, the corresponding sensing mechanisms of SnO 2 -based gas sensors of these fault characteristic gases are comprehensively discussed. In the final section of this review, the major challenges and promising developments in this domain are also given.