Study On Gas Sensing Properties Of Metal Oxide Composites Based On Carbon Nanohorn And MXene

Traditional metal oxides have become a research hotspot in the field of gas sensors because of their low cost,simple preparation method and controllable operation.However,in practical production and application,the defects of metal oxide gas sensor such as low sensitivity,high working temperature,poor stability and short service life limit its rapid development in the direction of gas sensor.Carbon Nanohorn（CNH）is a kind of carbon nano material with ox horn shape.Compared with rod carbon nanotube and layered graphene,CNH has a unique spherical morphology.It has attracted extensive attention because of its large specific surface area,strong thermal stability and high porosity.Ti₃C₂T_x（MXene）is a new two-dimensional material and first synthesized by Gogotsi et al.in 2011,and has been widely studied in the fields of lithium-ion batteries,supercapacitors,catalysis,sensors and so on.The combination of CNH and Ti₃C₂T_xwith metal oxide can effectively overcome the defects of traditional metal oxide gas sensor and improve the gas sensing performance of gas sensor.Based on this,this paper mainly includes the following three parts:（1）In₂O₃/CNH nanocomposites with different CNH contents were prepared by solvothermal method.The structure and morphology of the synthesized nanocomposites were studied by XRD,FESEM,TEM,EDS,XPS and BET,which confirmed the successful synthesis of In₂O₃/CNH nanocomposites.The H₂S sensing performance of the sensor based on them was tested at the operating temperature of 40℃ to 300℃.The results show that the best sample is In₂O₃/CNH（2 wt%）nanocomposite.The sensor is in 2 ppm H₂S,the operating temperature is 70℃,and the sensitivity is close to 3000（R_a/R_g）.The sensor shows good selectivity,low humidity effect,good reproducibility and stability.The explanation for the improvement of sensor performance is mainly related to the formation of p-n junction between In₂O₃,which determines the bending of surface energy band and the increase of sensor response.It also provides a set of possible explanations for sensor effects.In conclusion,it is confirmed by experiments that In₂O₃/CNH nanocomposites can be used as a powerful candidate for low-power and high-performance H₂S detection.（2）As a new two-dimensional（2D）material,Ti₃C₂T_xshows a greater application prospect in NH₃detection at room temperature.However,the detection sensitivity of original Ti₃C₂T_xto NH₃is low.Ti₃C₂T_x/In₂O₃composites were successfully synthesized by simple ultrasonic technology.Ti₃C₂T_x/In₂O₃composite sensor has 63.8%（|R_g-R_a|/R_a×100%）of 30 ppm NH₃at room temperature,which is 30.4 times higher than that of pure Ti₃C₂T_xsensor.The influence of relative humidity on the gas sensing performance of NH₃gas sensor is systematically studied.In addition,the sensor shows stable repeatability,long-term stability and excellent selectivity for NH₃.Finally,it shows that Ti₃C₂T_x/In₂O₃sensor has broad application prospects in detecting NH₃at room temperature.And this simple ultrasonic bonding method can be extended to other MXene metal oxide bonding applications.（3）Triethylamine（TEA）gas is one of the volatile organic compounds（VOCs）harmful to human health and ecological environment.Therefore,in order to prevent the harmful effects of TEA gas,it is necessary to detect it accurately.Cu₂O has low response to TEA gas and slow response recovery.Cu₂O/Ti₃C₂T_xnanocomposites were prepared by simple ultrasonic technology.Cu₂O is evenly dispersed on the surface and between layers of multilayer Ti₃C₂T_xto form a stable hybrid heterostructure.The best Cu₂O/Ti₃C₂T_xnanocomposite sensor has a response of 181.6%（|R_g-R_a|/R_a×100%）to 10 ppm TEA gas at room temperature,which is 3.5 times higher than the original Cu₂O nanospheres（52.1%）.In addition,because Ti₃C₂T_xhas the characteristics of high carrier mobility and good conductivity,the response recovery time（1062 s/74 s）of Cu₂O/Ti₃C₂T_xnanocomposite is much faster than that of original Cu₂O（3169 s/293 s）.Moreover,Cu₂O/Ti₃C₂T_xnanocomposite sensor also has good repeatability,selectivity and long-term stability.It can be seen that Cu₂O/Ti₃C₂T_xnanocomposite sensor has broad application prospects in detecting TEA gas at room temperature.