| Summary: | 碩士 === 國立臺灣科技大學 === 電子工程系 === 106 === Hydrogen (H2) is known as clean energy source for future generation requirements. However, it is dangerous when leak about 4 vol % in the atmosphere, therefore it is essential to sense with suitable sensors. At present, there are many types of the commercially available H2 sensors with semiconductors so on. In this context, ZnO materials have gained significant attention in hydrogen gas sensing applications due to their excellent properties. However, the stability, poor response time and inferior recovery at room temperature limit their use in high-performance real-time gas sensors. Herein, we report highly enhanced H2-gas-sensing performance of a TiO2-doped ZnO hybrid composites on graphene substrate.
First section of this study focus on the fabrication of hybrid gas sensors using TiO2-doped ZnO nanorods (TiO2-ZNR). In the second section, we develop novel nanostructure using TiO2-ZNR composites on graphene substrates and studied their structural and gas sensing properties. The systematic investigations were revealed that adding different amount of TiO2 in the hydrothermal process of ZNRs, strongly influence the gas sensing performance. The TiO2-ZNR based gas sensor shows superb enhancement in hydrogen sensitivity of 54.9 % comparing to ZNR gas sensor (26.3%). It is believed that the TiO2 nanoparticles onto ZNR induces more active sites for the adsorption of O2. Moreover, the electrons transfer from conduction band of TiO2 to that of ZnO, leading to higher conductance of TiO2-ZNR nanocomposites than that of the pure ZNR.
Finally, TiO2-doped ZNR hybrid composites on graphene exhibits an ultrahigh sensor response even at small detection level. This TiO2-doped ZNR/Graphene hybrid sensors exhibits the superior sensitivity of 75.6%, which is overwhelmingly better than ZNRs (26.3%), TiO2-ZNR (54.9 %) and ZNRs/graphene (53.6 %). The enhancement is due to the efficient O2 defects in the TiO2-doped ZNR/graphene hybrid, also, the chemisorbed O2 ions in the surface react with H2, leading to desorption of H2O, and release a huge number of electrons to the conduction band. Thus, the accumulation layer is formed and the depletion region is decreased and enhanced the sensitivity. The outstanding features such as selectivity, stability and repeatability of TiO2-doped ZNR/Graphene, makes them as a promising candidate for high performance gas sensors.
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