Preparation Of Oxide/Mxene Nanocomposites And Their Gas Sensing Properties

Acetone is a common chemical solvent and raw material in the industry.It is volatile,flammable and easy to explode in the presence of open fire,and has certain toxicity.In addition,there is a higher level of acetone gas in the breath of diabetic patients than the impatients.Therefore,the detection of acetone is of great significance both for the safety of industrial production and as a diagnostic method for important expiratory markers of diabetic patients to protect people’s health.The main research contents and results of this paper are as follows:Semiconductor oxides have become an important class of gas sensor materials due to their abundant sources,low cost,simple preparation,and high stability.Zinc oxide（ZnO）and tin oxide（SnO₂）have received particular attention in the sensor field in recent years due to their excellent chemical stability,low cost,structural diversity,and controllability.However,the existing ZnO and SnO₂still have shortcomings such as relatively low response and relatively high detection limit.To this end,this paper proposes an innovative idea of using emerging two-dimensional Mxene materials and metal oxides ZnO and SnO₂to construct heterostructures,and conducts material preparation and acetone gas sensing properties.The main results are as follows:（1）Using Ti₃AlC₂MAX phase as raw material,Ti₃C₂T_xMxene sheets were prepared by hydrofluoric acid etching method.Comparing the XRD patterns of Ti₃AlC₂MAX before and after acid etching,it is found that the（004）crystal plane of Ti₃AlC₂disappears,indicating that Alhas been removed from Ti₃AlC₂MAX phase.The interlayer spacing D can be calculated by the Scherrer formula to be 1.42 nm.SEM results of the samples after acid etching showed that the Ti₃C₂T_xnanosheets are typical layered structures.The effects of different intercalating agents DMSO,DMF and TMAOH on the expansion of Ti₃C₂T_xmaterials were studied.SEM results showed that these intercalating agents could effectively expand the Mxene layer,but the peeling efficiency of different intercalating agents was different,showing the law of TMAOH>DMSO>DMF.TMAOH has the best effect of peeling off the Mxene sheet.Its peeling efficiency is the highest.The solution with a few-layer Mxene prepared by TMAOH peeling could be seen that the pure phase Mxene is in the form of flakes with a lattice spacing of 0.26 nm under the transmission microscope.（2）ZnO/Ti₃C₂T_xcomposites were synthesized by hydrothermal method.The effects of multi-layer Mxene and few-layer Mxene on the gas sensing properties of ZnO/Mxene composites were studied.The results showed that the few-layer Mxene solution had better gas-sensing properties.ZnO/Ti₃C₂T_xcomposites containing different proportions of Ti₃C₂T_xwere prepared,and the effects of different proportions of Mxene content on the gas sensing properties of ZnO/Ti₃C₂T_xcomposites were compared.It was found that the ZnO/Ti₃C₂T_xcomposites containing 2wt.%Ti₃C₂T_xhad the highest response to acetone.ZnO with thin layer morphology was prepared by PVP,and ZnO/Ti₃C₂T_xcomposites were prepared by compounding it with Mxene solution.The effect of different morphologies of ZnO on the gas sensing properties of ZnO/Ti₃C₂T_xcomposites was studied.The results showed that the granular ZnO/Mxene composite had a higher response to acetone,14.3,which was better than that of the flake ZnO/Mxene composite.The response value of the ZnO/Mxene composites increased to 17.8 after doping with Ni ions.（3）The SnO₂-ZnO/Ti₃C₂T_xcomposite was synthesized by hydrothermal method,and the SEM study found that SnO₂-ZnO was uniformly distributed on Ti₃C₂T_x.SnO₂was doped with a small amount of Zn element to form a heterojunction between SnO₂and ZnO.The sensor had a response value of 22.1 to 100ppm ethanol gas at 270℃,and has a maximum response value of 30.96 for 150ppm ethanol gas,which is three times as much as that of SnO₂/ZnO.The selectivity is better.The sensor had a response value of 4.39 when the ethanol concentration was 10 ppm,indicating that the MSZ sensor had a low detection limit for ethanol and had a wide range of application scenarios.In this paper,the preparation of composite materials composed of metal oxides ZnO,SnO₂and two-dimensional material Mxene was carried out.The reason why the composite of metal oxide and two-dimensional material Mxene improved the gas sensing performance was studied.The intrinsic sensing mechanism of ZnO,SnO₂metal oxide and Mxene composites was revealed.The research results show that the composites composed of metal oxides/Mxene have good application prospects in the sensor field.