| Summary: | 博士 === 靜宜大學 === 應用化學系 === 107 === In this study, a metal oxide semiconductor gas sensor was selected for this research. Over the past few years, the biggest drawback of this type of sensor was the need to warm the element for sensing, which was disadvantageous for commercial applications. There are many research dedicated to the development of sensing elements that can be applied at room temperature now. In this research, it was attempted to change the structure of different metal oxides and to compare their sensing efficiencies. There had three different material structures been prepared in this research, including core-shell structure, Mesoporous structure and Composite material. At the core-shell structure, platinum is selected as the core and the shell is used nickel oxide. At the mesoporous structure material used WO3 (Mesoporous WO3, M-WO3), and is doping with palladium. The large surface area of the mesoporous structure and the doping Pd can increase the sensing effect. The composite material was used WO3-TiO2 applied to hydrogen gas sensing. This research will investigate the hydrogen sensor response (S), response time (T90, s), recovery time (Tr90, s) of the sensing elements fabricated from different structural materials at room temperature and compare them with other research, and using XRD, TEM, EDS, and BET were used to characterize the structure of the material and hydrogen sensing experiments were performed. In the XRD and EDS patterns, it can be confirmed that the prepared Pt@NiO, M-WO3, and WO3-TiO2 samples contain no other impurities, and the core-shell structure of Pt@NiO can be clearly seen from the TEM image, prove successful synthesis of Pt@NiO core-shell particles. In the TEM image of M-WO3, the pore distribution state of M-WO3 and the worm-like micropore on the surface of the material can also be clearly seen. It can be seen from the TEM image that WO3-TiO2 has been successfully synthesized and has different pore distributions at the same time, so that the material has a high specific surface area to increase the sensing effect.
The results show that whether it is core-shell structure (Pt@NiO), mesoporous structure (M-WO3) or composite material (WO3-TiO2), all of them can be measured at room temperature sensing hydrogen response. The sensing element made with Pt@NiO at a Pt to Ni molar ratio of 1:30 (Pt: Ni = 1:30) for 5000 ppm hydrogen has the best sensor response, S = 4.25. A sensing element (1.0 wt% Pd/M-WO3) made by M-WO3 doping 1.0 wt% Pd, also sensing hydrogen gas at 5000 ppm, S= 11.8. The composite material by WO3 and TiO2 when the ratio of WO3 is 1.0 wt% (1.0 wt% WO3-TiO2), S= 5.62. The sensing elements made of three different structural materials proposed in this research have a fast recovery time (Tr90) for hydrogen gas sensing. The recovery times of Pt@NiO, 1.0 wt% Pd/M-WO3, 1.0 wt% WO3-TiO2 were 8 s, 10 s and 5 s respectively. In this research, three materials demonstrate the potential for application to room temperature hydrogen sensors.In this work, we will investigate the mechanism of three different structures in hydrogen gas sensing and discuss the material structure of the influence for sensor response.
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