Research On Preparation And Performance Optimization Of Gas Sensing For Toluene Gas Sensor

Toluene is an industrial raw material,which long-term exposure can easily cause blood system and respiratory diseases,so it is very important to detect toluene.Traditional MOS gas sensors have the advantages of low cost and portability,but they also have the disadvantages of poor stability,high humidity influence and poor selectivity.In this paper,Co₃O₄ NWs（nanowire）was prepared by template method,and the gas sensitive performance optimization and theory research were carried out.The main contents are as follows:（1）Single Co₃O₄ NWs and Co₃O₄ NWs were prepared by nano-casting method using hard template SBA-15 and centrifugal separation technology.The gas sensitivity results show that,under the same microstructure,the single Co₃O₄ NWs has a higher surface area(44.98 m²g^-1)to provide more surface oxygen and toluene gas adsorption,so it has a better gas sensitivity performance at 210℃.（2）Mesoporous Co₃O₄ NWs doped with different valence state cations（Zn,In and Sn）and the same valence state of different concentration were synthesized by nano-casting method.The results show that the doping could not affect the microstructure of the sample,and the Co_2.841Sn_0.106O₄ NWs sensor has the highest response value to toluene（7.28）.Due to appropriate ion doping,the surface area is improved to form a thicker hole accumulation layer and R_a is reduced,while high-valence doping provides excess electrons to combine with the hole and increase R_g,thus improving the gas response.（3）Co₃O₄ NWs were synthesized by nano-casting method and loaded with Ag particles of different concentrations.The results show that the presence of Ag particles reduces the operating temperature from 210℃to 190℃,and increase the reaction value to 15.323.The mechanism of gas sensitivity optimization can be explained from two aspects:chemical sensitization and electron sensitization.Due to the catalytic activity of precious metal Ag,more effective adsorption sites can be provided to optimize the gas sensitivity.（4）Co₃O₄ NWs were synthesized by nano-casting method and then compounded with different concentrations of C₃N₄.The results show that the contact interface between C₃N₄ and Co₃O₄ forms p-n heterojunction,which leads to the increase of barrier width and decrease of R_a.At the same time,compound C₃N₄ can provide more effective active sites,increase R_g and improve sensitivity.Therefore,the sensitivity of（C₃N₄）_0.36Co₃O₄ NWs to toluene（17.015）is 6 times that of Co₃O₄NWs（2.839）.