Study On Gas Sensing Characteristics Of RGO/MOFs Derived Metal Oxide Heterojunction

With the development of society,environmental pollution issues have also emerged,posing a threat to people’s lives and health.Therefore,it is very important to design a gas sensor with high sensitivity,fast response and good selectivity for the detection of toxic and harmful gases in the air.Metal oxide semiconductor（Metal Oxide Semiconductor,MOS）is one of the most widely used and best performance gas sensitive materials at present.However,a single MOS based sensor will also have some problems,such as high operating temperature,poor selectivity,slow response and so on.Therefore,in this paper,metal oxides were prepared by using metal organic framework（Metal-Organic Frameworks,MOFs）as sacrificial template,and then reduced graphene oxide（r GO）was introduced by hydrazine hydrate reduction,and three kinds of gas sensing materials Co₃O₄/r GO,Zn O/r GO and Zn O/Co₃O₄/r GO were successfully synthesized.The effects of morphology,graphene content and heterojunction on the gas sensing properties of the sensor were investigated.Using ZIF-67 as a sacrificial template,Co₃O₄ was obtained by pyrolysis,and r GO was further introduced by hydrazine hydrate reduction,and Co₃O₄/r GO composites were successfully synthesized.Through the gas sensitivity test,it was found that Co₃O₄/r GO-0.5 showed good selectivity to 20 ppm triethylamine,and the response value at the working temperature of 140℃was 24.9.Using ZIF-8 as a sacrificial template,a series of ZnO/rGO composites with different graphene contents were obtained by pyrolysis and chemical reduction.The gas sensitivity test results show that the response value of Zn O/r GO-0.25 to 20 ppm triethylamine at the working temperature of 200℃is 152.2,and the detection limit is1 ppm.A series of ZnO/Co₃O₄/r GO composites have been prepared by controlling the molar ratio of cobalt and the content of graphene using methods such as coprecipitation,thermal decomposition,and chemical reduction.It was found that when the molar ratio of cobalt atoms was 0.05,the performance of Zn O/Co₃O₄ is the best.Then,Zn O/Co₃O₄-0.05 was used as the main material for composite graphene.The results show that Zn O/Co₃O₄ nanoparticles are evenly distributed on r GO and increase the specific surface area when the r GO content is 0.5 wt%.In the gas sensitive performance test,Zn O/Co₃O₄/r GO-0.5 has a high response value of 528.5 to 20 ppm triethylamine at300℃,and the response/recovery time is only 31 s/16 s.