Preparation Of Fe₂O₃-coated ZnO Nano-Hollow Structure And Study On Gas Sensing Performance

With the rapid development of industrialization and urbanization of human society,air pollution and the leakage of toxic and harmful gases continue to endanger public safety,people’s property and health.As a detection device for gas composition and concentration,gas sensors can effectively detect,monitor and identify gases.Metal oxide semiconductor（MOSs）-based gas sensors have been valued because of their advantages of easy preparation,simple structure and low cost of sensitive materials,and have great application prospects and commercial value.With the endless pursuit of advanced gas sensors,designing micro-nanoporous structures for metal oxide semiconductors and exposing more surface-active surfaces to improve gas sensing performance has become an important means in the field of materials and gas sensing research.In recent years,researchers have focused on metal-organic frameworks（MOFs）to prepare MOSs gas-sensitive materials with high porosity,high specific surface area and high reactive site by self-sacrificing template method,and on this basis,further improve the gas-sensitive performance of sensitive materials by doping and compounding.In this paper,hollow ZnO was prepared using ZIF-8 as a sacrificial template,and the formation of n-n-type ZnO@Fe₂O₃ heterojunctions by Fe doping and Fe₂O₃ recombination was carried out,and their gas-sensing properties were tested,their growth mechanisms were revealed,and the relationship between nanostructure and gassensing properties is discussed.The main research contents of this paper are as follows:（1）ZIF-8 dodecahedral prepared by chemical precipitation method has smooth surface,good monodispersity,and a size of about 520 nm,and the influence of ligand2-Me IM on product morphology and structure is discussed,and the ZnO hollow dodecahedron obtained after annealing has a rough surface and a size of about 500 nm,and the influence of annealing conditions on product morphology and structure and its annealing formation mechanism are discussed.（2）Fe-doped ZIF-8 dodecahedron with good dispersion and uniform size and structure was prepared by chemical precipitation method,with a size of about 500 nm,and the influence of metal salt ratio on product morphology and structure was discussed,and the Fe-doped ZnO hollow dodecahedron obtained after annealing had a size of about 400 nm and a specific surface area of 48.31 m²g^-1.Fe-doped ZnO hollow dodecahedron-based gas sensor has a response time of 0.9 s and 9 s for 200 ppm ethanol at an optimal operating temperature of 330 °C,which is about twice as high as that of pure phase ZnO.The sensitivity of Fe-doped ZnO hollow dodecahedral to ethanol has a good linear relationship with the increase of its concentration,and the sensitivity to200 ppm ethanol can reach 31.3.（3）Fe₂O₃ was combined with ZnO by hydrothermal synthesis,and then annealed to form ZnO@Fe₂O₃ n-n heterogeneous hollow cubes with a size of about 500 nm and a specific surface area of 85.3 m²g^-1,and the influence of hydrothermal reaction time on the dispersion of Fe₂O₃ nanorods and the mechanism of heterojunction gas sensitivity were discussed.The response time and recovery time of the gas sensor based on the ZnO@Fe₂O₃ heterogeneous structure were 2 s and 7 s for 200 ppm ethanol at an optimal operating temperature of 240 °C,and the sensitivity of ZnO@Fe₂O₃ n-n heterogeneous hollow cubes to ethanol increased in a good linear relationship with its concentration,and the sensitivity to 200 ppm ethanol was 9.3,although the sensitivity was reduced compared with pure phase ZnO,but the recovery time was improved by about 16 times.In summary,ZnO@Fe₂O₃ n-n heterojunction hollow cubic structure materials were prepared in two steps,and applied to the gas detection of ethanol for the first time,and had excellent gas sensing performance.