Preparation And Gas Sensing Properties Of ?-Fe₂O₃@2D Layered Composites

As air pollution is becoming more serious,efficient and inexpensive systems for detecting and quantifying harmful gases are becoming increasingly important.Gas sensors are considered a promising alternative to environmental measurements due to their low cost,high sensitivity,fast response and direct electronic interface.Metal oxide semiconductors are the most promising candidates because of their low cost,high sensitivity,fast response/recovery time,simple electronic interface,ease of use,and the ability to detect large amounts of gases.Among them,?-Fe₂O₃ is widely used in the field of gas sensors due to its environmental friendliness,low preparation cost and high stability,ect.Graphene has been favored by researchers in the field of gas sensors in recent years,which has a large specific surface area,electrical conductivity and thermal conductivity.However,its high temperature resistance is poor,and it is easily oxidized at high temperatures,resulting in collapse of the structure,which is extremely disadvantageous for the control and detection of gas sensitivity.Graphene-like two-dimensional materials?graphite,h-BN,MoS₂?not only have many properties similar to graphene in performance,but also have high temperature resistance and antioxidant which are not possessed by graphene.Therefore,it is particularly important to prepare gas-sensitive materials with high sensitivity,high selectivity and fast response/recovery rate by combining the advantages of layered two-dimensional material?graphite,h-BN,MoS₂?and?-Fe₂O₃ in the study of gas sensors.The main research contents of this paper are as follows:1?The?-Fe₂O₃@graphite nanocomposite was prepared by low temperature hydrolysis precipitation method and calcination treatment,which is composed of porous?-Fe₂O₃ nanorods with a pore size of about 3.7 nm and graphite nanosheets.Compared with pure?-Fe₂O₃,?-Fe₂O₃@graphite nanocomposites have enhanced sensing properties.The response of?-Fe₂O₃@graphite?12 h?nanocomposites to 50ppm acetone reached a maximum of 16.9 at an optimum temperature of 260°C,which was 2.2 times of pure?-Fe₂O₃.The improvement in sensing performance is attributed to the porous structure of?-Fe₂O₃@graphite nanocomposites,high specific surface area,p-n heterostructure and high temperature stability of graphite.2?The precursor?-FeOOH/h-BN nanocomposites were successfully prepared by simple and easy operation and green low temperature hydrolysis precipitation method.Further,the sandwich-like?-Fe₂O₃/h-BN nanocomposites were obtained by calcination.The results show that the porous?-Fe₂O₃ nanorods with a rod length of about 100-200nm are anchored on the h-BN nanosheets in an orderly manner.The high temperature gas sensor based on?-Fe₂O₃/h-BN nanocomposite has a response value of 10.2 to 50ppm acetone at an optimum operating temperature of 320°C,which is about twice of?-Fe₂O₃.Its response/recovery time is 8/4 s.The enhanced acetone performance exhibited by?-Fe₂O₃/h-BN nanocomposites can be attributed to the porous structure of?-Fe₂O₃/h-BN nanocomposites,large surface area,p-n heterojunctions that can adjust the space charge layer and the addition of h-BN effectively inhibited the agglomeration of?-Fe₂O₃ nanorods.3?The porous?-Fe₂O₃@MoS₂ nanocomposites was prepared by low temperature hydrolysis precipitation and calcination.The?-Fe₂O₃ nanorods in?-Fe₂O₃@MoS₂nanocomposites have a rod length of about 100 nm and a pore size of about 4 nm.The response of?-Fe₂O₃@MoS₂-based sensor is 11.6 to 50 ppm acetone at an optimum operating temperature of 280°C,which is about 2.3 times of?-Fe₂O₃.Its response/recovery time is 5/4 s.The enhanced acetone performance exhibited by?-Fe₂O₃@MoS₂ nanocomposites can be attributed to the porous structure of?-Fe₂O₃@MoS₂ nanocomposites,large surface area,heterojunction and synergy between?-Fe₂O₃ and MoS₂,the effect and the role of the"conducting network"played by MoS₂.