Preparation And Gas Sensing Properties Of Ti₃C₂T_x-（MgGa₂O₄, ZnGa₂O₄, CuGaO₂） Composite Materials

The sharp increase of harmful gas emissions has caused great hidden dangers to people’s health,such as formaldehyde in newly decorated houses and trimethylamine released after the death of fish organisms.Traditional detection methods such as gas chromatography and mass spectrometry have disadvantages such as high cost and inconvenience to carry,so they cannot be used in a wide range of applications.Due to the advantages of simple operation and low cost,the gas sensor has the potential applications for detecting toxic and harmful gases.This paper gives a brief overview of the research background and practical significance of the research firstly,and briefly describes the classification,performance indicators,sensing mechanism and methods to improve the gas sensing performance of gas sensors.MXene have been widely used in gas sensor devices,photocatalysis,energy storage and other fields because of their graphene-like two-dimensional structure,large surface area,surface hydrophilicity,metal conductivity and excellent electrochemical properties.In this paper,Ti₃C₂T_x-（MgGa₂O₄、ZnGa₂O₄、CuGaO₂）composites were synthesized by hydrothermal method,a series of characterization methods and their gas sensing properties were tested.The effects of doping amount of Ti₃C₂T_x in different proportion on the gas sensing properties of the composites were studied.In Chapter 2,Ti₃C₂T_x was prepared by etching Ti₃AlC₂ with concentrated hydrochloric acid and ammonium fluoride,then we prepared Ti₃C₂T_x-MgGa₂O₄composites by hydrothermal method.The gas sensing results showed that MGO-3（15wt%Ti₃C₂T_x-MgGa₂O₄）composite materials had the best sensitivity of 15 to 100ppm ethanol at room temperature,and the response and recovery times were 253 s and118 s respectively.The minimum detection limit to ethanol was 1 ppm.The sensitivity of MGO-3 composite material to other VOCs were all less than 2.In Chapter 3,Ti₃C₂T_x-ZnGa₂O₄ composite were prepared by hydrothermal method.The gas sensing experiment results show that the sensitivity of ZGO-2（10wt%Ti₃C₂T_x-ZnGa₂O₄）composite materials to 100 ppm formaldehyde at room temperature was 7.4,the response and recovery time were 41.4 s and 28.8 s respectively,and the minimum detection limit was 0.1 ppm.The sensitivity of ZGO-2 composite material to other VOCs were all less than 1.5.Compared with pure ZnGa₂O₄ material,the sensitivity of ZGO-2 composite material to formaldehyde was increased by 7.4 times.In Chapter 4,Ti₃C₂T_x-CuGaO₂ composite were prepared by hydrothermal method.The results of gas sensing experiment showed that CGO-2（3wt%Ti₃C₂T_x-CuGaO₂）has the highest sensitivity and good selectivity to ammonia at 200^oC.The sensitivity to100 ppm ammonia was 7,the minimum detection limit was 0.1 ppm,and the response and recovery time were 28 s and 14.7 s respectively.Compared with pure CuGaO₂,the sensitivity value was increased by 7 times and the selectivity was improved.The sensitivity of CGO-2 composite materials to other VOCs were all less than 2.5.