Preparation And Gas Sensitive Properties Of Ti₃C₂T_x MXene Derived-TiO₂ And Its Nanocomposites

China is a big machine manufacturing country,cutting,welding,casting process will produce a large number of H2S,NO2,NH3 and other harmful gases,pollute the ecological environment at the same time seriously threaten people’s health and safety,and the development of high-performance real-time detection gas sensor is regarded as an effective way to balance the contradiction between production and life.In the composition of gas sensor,gas sensitive material plays a decisive role in the performance of the sensor.Therefore,it is one of the effective ways to improve gas detection performance to design highly sensitive gas sensitive materials.In this paper,the novel two-dimensional material Ti3C2Tx MXene,combined with traditional materials synthesis method,has successfully prepared two-dimensional sheet structure of TiO2 nanomaterial,and at the same time,it has the noble metal activation effect of Ag nanoparticles and 0D ZnO composite as a gas sensitive material.A gas sensor with high sensitivity is successfully assembled,and the gas sensitivity performance and practical application value of the system are evaluated systematically.The Al layer of precursor Ti3AlC2 was etched with hydrochloric acid and lithium fluoride to obtain a single layer of Ti3C2Tx MXene.The M-TiO2 derivatives with intact morphology were obtained by heat treatment at 400℃ and 50h in air with Ti3C2Tx MXene as titanium source.Using the gas sensitive test platform to change the test environment temperature,M-TiO2 showed the best gas sensitive performance to H2S under the test condition of 125℃.When the concentration of H2S rises to 80 ppm,the response value of M-TiO2 reaches 14.15.The logarithm Log(R)of the sensor response value and logarithm Log(C)of the concentration of H2S show a strong linear relationship in the range of concentration.After 16 days of continuous testing of 10,20 and 40 ppm H2S,the performance still reached 92%of the initial response value.After 10 cycles of 10 ppm H2S,the sensitivity did not decrease significantly.In the 20 ppm interference gas,it can be seen that the gas response value to H2S is about twice that of other gases.Ag nanoparticles were uniformly loaded onto TiO2 nanosheets by heat treatment and thermal reduction method.The effects of heat treatment temperature,Ag to M-TiO2 ratio and other process parameters on the morphology and gas-sensitive properties of the products were systematically investigated.Through the corresponding test,it was found that Ag@M-TiO2 prepared under the condition of thermal reduction at 450℃ and 4 h,and the mass ratio of Ag to TiO2 was 1:20,showed the best gas-sensitive performance.Ag@M-TiO2 sensor response to 50 ppm NH3 is calculated to be 71.8,15 times higher than TiO2 sensor;The sensor showed a stable and repeatable dynamic response with no significant reduction in sensitivity.After 16 days of long-term stability measurement,the sensor still maintained the initial response value of～87.1%.When exposed to 25 ppm of various interfering gases,the response value of Ag@M-TiO2 to NH3 is at least one order of magnitude higher than that of any other interfering gases.The humidity resistance test of 25 ppm NH3 shows that the Ag@M-TiO2 sensor maintains a response value of 18.3 even at high humidity(90%).Through the van der Waals force interaction between Ti3C2Tx MXene and ZnO and the chemical interaction between ZnO nanoparticles and the residual oxygen-containing functional groups on Ti3C2Tx MXene,ZnO was in situ self-assembled on the surface of Ti3C2Tx MXene.Then after 500℃,36 h heat treatment to get ZnO@M-TiO2.When the mass percentage of ZnO is 80%and the added NaOH is 10 mg/mL,the optimized ZnO@M-TiO2 is obtained.The synergistic effect of ZnO and M-TiO2 shows good gas-sensitive performance.The sensor response values of ZnO@M-TiO2 sensor to 0.5 and 4 ppm NO2 are calculated as 2.1 and 42.5,respectively.ZnO@M-TiO2 The sensor maintained～76%of the initial response after 16 days of exposure to 2 ppm NO2;The response to 1 ppm NO2 under different humidity conditions of 0%to 80%changed from 3.3 to 1.8,with a range of～45%.