The Construction Of Gallium-based Nanocomposites And Their Gas-sensing Properties

A large amount of industrial waste gas emissions dramatically increase the concentration of NO_x in the atmosphere,which poses a serious threat to human health.Therefore,it is imminent to develop gas sensors which can monitor NO_x in real-time.Metal oxide semiconductors are widely used as high-quality sensing materials in gas sensing.In this paper,gallium-based composites were synthesized in three different paths.The gas-sensing performance and mechanism were systematically studied with a series of characterization and testing methods.The main research contents of this paper include:1.The Ga₂O₃/Al₂O₃ composite with p-type conductivity was synthesized by hydrothermal and subsequent calcination.The morphology,band structure and semiconductor types of the composite were studied by a series of characterization methods.The gas-sensitivity test results show that Ga₂O₃/Al₂O₃ composites have excellent NO_x detection capabilities at room temperature.The improvement of the gas-sensitive properties of composite is closely related to large specific surface area and a large amount of surface adsorbed oxygen.Moreover,a reasonable gas sensor model is proposed to elaborate on the mechanism of n-p conversion.2.The Ga OOH/Co₃O₄ composites with n-p heterojunction structure were obtained by pyrolysis of ZIF-67 and subsequent vacuum stirring.The XRD and FTIR results show that the components of the composite are Co₃O₄ and Ga OOH.The N₂adsorption-desorption tests indicated that the composite has a large specific surface area and rich pore structure.The Mottschottky test proves that the composite material has an n-p heterostructure.The gas sensing test results show that the Ga OOH/Co₃O₄ composite has an excellent ability to detect NO_x at room temperature.Moreover,the role of n-p heterojunction in improving gas sensing is studied.3.The Ga OOH/PEI-CNT composites were synthesized by loading Ga OOH onto the surface of PEI modified CNTs through a one-step hydrothermal method.The EIS electrochemical tests show that CNTs improve the electrochemical performance of the composite.The Ga OOH/PEI-CNT composite has better NO_x gas sensitivity than pure Ga OOH material.Studies have shown that the improvement of the gas-sensing performance of composite materials is mainly related to its large specific surface area,higher carrier mobility and the synergistic effect of CNT and Ga OOH.