Preparation Of Metal Oxide/3D RGO Nanocomposites And Research On Gas-sensing Properties At Room Temperature

With the rapid development of global economy and the continuous improvement of industrial level,the global environmental pollution problem is increasingly serious.The problem of gas pollution in human life has always been the focus of researchers.There are many kinds of harmful gases in the air.Currently,nitrogen dioxide?NO₂?,ammonia and aldehyde gases,which are well known by human beings,are very troublesome pollutants threatening human health.Therefore,the effective detection of them is of great practical significance.Metal oxide based gas sensors have been widely used in civil,industrial and atmospheric pollutant detection.However,the disadvantages of metal oxide based gas sensors,such as high energy consumption,low conduction and weak identification ability,have become the bottleneck of their development.As a new generation of functional materials,graphene has been widely used in the field of gas sensing due to its excellent conductivity,large specific surface area and good electron mobility at room temperature,which can effectively make up for the deficiency of metal oxide gas sensing materials.Therefore,this paper systematically studies the gas-sensitive properties of metal oxide/graphene composites at room temperature or low temperature.Three dimensional reduced graphene oxide aerogel?In₂O₃/GAs?GAs sensor based on indium oxide?In₂O₃?nanocomposite was developed.In this paper,In₂O₃/GAs nanocomposites were obtained by hydrothermal method combined with freeze-drying technology.In₂O₃ nanospheres with a diameter of about 115 nm were evenly distributed in the porous graphene channels,forming a close contact between them.In₂O₃/GAs nanocomposite exhibits high sensitivity and rapid response recovery rate when TMA GAs is tested at room temperature.Its sensitivity to TMA GAs with concentration of 100 ppm is15.2%,response time is 1 s,recovery time is 1 s,and it also shows excellent cyclic stability and GAs selectivity.The construction of p-n heterostructure and abundant pore channels provide channels for the transport of electrons and the diffusion of GAs molecules,thus promoting the In₂O₃/gas-based GAs sensor to show better GAs sensitivity to TMA GAs at room temperature.The heterogeneous structure of iron oxide/three-dimensional reduced graphene oxide aerogel??-Fe₂O₃/GAs?was constructed and its GAs sensitivity at room temperature was studied.The morphology analysis showed that a porous conductive network was constructed between the?-Fe₂O₃ nanoparticles and GAs with high conductivity.The growth and agglomeration of?-Fe₂O₃ nanoparticles were effectively restricted by GAs,while the smaller?-Fe₂O₃ nanoparticles effectively inhibited GAs stack.The abundant pore channels in?-Fe₂O₃/GAs aerogel facilitate the full contact between GAs molecules and sensitive materials and the formation of p-n junction between the two components,so that?-Fe₂O₃/GAs aerogel shows excellent sensitivity and rapid response recovery characteristics at room temperature.The sensitivity of this composite material to NO₂ gas with concentration of 50 ppm was 14%,the response time was 11 s,and the recovery time was 6 s.At the same time,a series of comparative experiments were conducted to further prove the dominant structure of?-Fe₂O₃/GAs aerogel.The presence of developed pores and heterojunctions in the structure can significantly improve the gas-sensitive performance of the material,and solve the problems such as the long recovery time of the gas-based GAs sensor at room temperature in the past.Copper oxide/three-dimensional reduced graphene oxide aerogel?CuO/GAs?with hollow hexahedral structure was designed and synthesized.The effects of its gas-sensitive properties at room temperature,the composite of p-type metal oxide CuO and the porous structure on its gas-sensitive properties were investigated.The experimental results show that CuO hollow hexahedron with a diameter of about 115 nm is uniformly dispersed in the three-dimensional pore channels of GAs aerogel material and no obvious agglomeration phenomenon occurs on the lamellar layer.The composite exhibits excellent gas-sensitive performance in response to NO₂ GAs at room temperature.Compared with rGO,the CuO/GAs aerogel has higher sensitivity and shows rapid room-temperature recovery performance.For NO₂ GAs with a concentration of 10 ppm,the CuO/GAs complex has a sensitivity of 59%,a response time of 1 s and a recovery time of 1 s,and a good working stability at room temperature.Compared with rGO,the special structure of CuO/rGO aerogel material provides a good gas sensing environment for the transmission,diffusion,adsorption and desorption of gas molecules,thus improving the sensitivity to NO₂ gas and accelerating the response recovery rate at room temperature.