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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.

In this paper, pure and Ag-doped SnO₂ nanospheres were synthesized by hydrothermal method and characterized via X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), and X-ray photoelectron spectra (XPS), respectively. The gas sensing performance of the pure, 1 at.%, 3 at.%, and 5 at.% Ag-doped SnO₂ sensing devices toward hydrogen (H₂) were systematically evaluated. The results indicated that compared with pure SnO₂ nanospheres, Ag-doped SnO₂ nanospheres could not only decrease the optimum working temperature but also significantly improve H₂ sensing such as higher gas response and faster response-recovery. Among all the samples, the 3 at.% Ag-doped SnO₂ showed the highest response 39 to 100 μL/L H₂ at 300 °C. Moreover, its gas sensing mechanism was discussed, and the results will provide reference and theoretical guidance for the development of high-performance SnO₂-based H₂ sensing devices., Competing Interests: The authors declare no conflict of interest.