Study Of The Effect Of Surface Functionalization On The Performance Of Benzenes Gas Sensors

With the substantial increase in industrial production and human activities in modern society,more and more air pollutants are being released into the atmosphere,causing certain threats to our health.Excess organic compound gases（VOCs）are very harmful to human body,such as irritation of human eyes and upper respiratory tract,as well as anesthetic effect on the central system.Among them,benzene gas mainly comes from automobile exhaust and building materials,which not only has a serious negative impact on the living environment,but also poses a direct danger to human health,so it is necessary to detect this kind of gas.The preparation of high-performance benzenes gas sensors has also become an important research goal for researchers.Selecting a suitable modification method is an important step in the study of gas sensors,where surface functionalization is one of the important ways to modify semiconductor-type gas sensors.On the one hand,the semiconductor and metal oxide composite to form a heterojunction can be used to combine the advantages of both materials to prepare gas sensors with higher performance;on the other hand,the surface of the semiconductor material can also be modified with noble metals,because noble metal nanoparticles have the advantages of uniform dispersion and high catalytic performance,which can enhance the gas-sensitive performance.Here,we selected metal oxide semiconductor WO₃and metal sulfide semiconductor SnS₂as the main materials to prepare semiconductor-type gas sensors by surface functionalization such as modification of metal oxide semiconductor to build heterojunction structure and introduction of bimetallic nanoparticles for the purpose of improving the sensitive characteristics of benzenes gas sensors.The mechanisms and reasons for the enhanced performance of gas sensors are also summarized and summarized.The details will be developed from the following aspects:（1）The metal oxide semiconductor WO₃was selected as the main object of the study,and a heterojunction was constructed to produce a sensor sensitive to toluene gas.Firstly,WO₃nanosheets were synthesized by hydrothermal method,and then RuO₂modified WO₃was obtained by ethylene glycol assisted reduction.By changing the content of RuO₂,the effect of different modification amounts on the gas sensing performance was explored.Specifically,the 0.5 wt%modified device exhibited a response value of 11.7 for 100 ppm toluene gas at 255℃,which is 6 times higher than that of the pure WO₃device,and reduced the operating temperature of the main material WO₃（302℃）.The device also has fast response and recovery times and is more selective,showing good linearity for different concentrations of toluene gas.The increased gas-sensitivity of the modified device is mainly due to the large surface area/volume ratio of WO₃,which is conducive to the adsorption of gas molecules,and the p-n heterojunction structure formed on the surface of RuO₂and WO₃materials,which leads to an increase in the initial resistance of the material.The enhancement of the adsorption capacity improves the gas sensitivity.（2）Metal oxides suffer from problems such as high operating temperatures.Next,we selected the two-dimensional metal sulfide SnS₂as the main material in order to prepare a device sensitive to benzene gas with a lower operating temperature.Firstly,a hydrothermal method was chosen to prepare the SnS₂two-dimensional sheet structure;secondly,a reducing agent was used to reduce chloropalladic and chloroauric acids into Au-Pd nanoparticles attached to the surface of the SnS₂nanosheets.The effect of bimetallic modification on the gas-sensitive properties was investigated by comparing the experimental test results of pure material,single-metal modification and bimetallic modification.Compared with pure SnS₂,the gold-palladium nanoparticles modified SnS₂exhibited better gas-sensitive properties for xylene gas.Specifically,the response value for 100 ppm xylene gas at 161℃reached 27.7,which is more than a tenfold increase compared to the pure material,and the optimal operating temperature was also reduced.The device was prepared with fast response and recovery times（4 s and 5 s）and excellent selectivity,especially for the differentiation of benzene,toluene and xylene gases.The significant improvement in gas-sensitive performance is attributed to the synergistic effect between gold and palladium nanoparticles,the boundary effect of the two-dimensional material and the formation of Schottky barriers.