Research On The Gas-Sensing Properties And Physical Mechanism Of Mesoporous Oxide Nanomaterials

With the continuous promotion of industrialization,environmental pollution problem is becoming more and more acute,and the treatment of waste gas,waste liquid,waste and other problems is becoming more and more urgent,and many of these gases will cause acute or chronic health effects on human body.Therefore,it is necessary for researchers to develop monitoring methods and instruments that can detect all kinds of flammable,explosive,toxic and harmful gases quickly and accurately.It is worth noting that metal oxide semiconductor has been widely used because of its low cost,low power consumption,reliability and simple usability.However,with the increasing demand for metal oxide semiconductor sensors with better selectivity and high sensitivity,more appropriate methods are needed to control the surface and internal performance.In this paper,the mechanisms of p-type and n-type gas-sensitive materials are studied.NiO nanowires and?-Fe₂O₃ with ordered mesoporous microstructure were constructed to enhance the response value,selectivity and stability to ethanol.In addition,two kinds of mesoporous NiO nanowires and mesoporous?-Fe₂O₃ nanowires were doped with different valence metal elements and p-n heterojunction was constructed.By adjusting crystal defects and carrier concentration,the gas sensing properties of the two materials were further improved.The main contents of this article are as follows:(1)Mesoporous Nickel oxides nanowires(NiO NWs)was prepared by nanocasting method with different valence metal cations doping,which using ordered straight channel mesoporous SBA-15 as hard template.All samples show the same mesoporous nanowire structure.According to the structure characterization,the specific surface area of mesoporous Ni0.963Fe0.037O1.018 and Ni0.966Sn0.034O1.034 NWS gas sensors are 35.62 m²/g and 59.37m²/g respectively,and the band gap width are 3.07 e V and 3.03 e V respectively.At 300?,the ethanol sensitivity of the two gas sensors to 100ppm ethanol gas are 20.485 and 17.844.Therefore,the high donor doping can effectively improve the gas sensing performance of the mesoporous NiO NWS gas sensor.(2)Mesoporous Nickel oxides nanowires(NiO NWs)was prepared by nanocasting method,which using ordered straight channel mesoporous SBA-15 as hard template,and then the Fe@NiO NWs were synthesized with the similar nanocasting procedure.The decorated ratio was adjusted to prepare mesoporous pure NiO,(Fe₂O₃)_0.016NiO and(Fe₂O₃)_0.027NiO NWs NWs.All test results show that the response value of 100 ppm ethanol gas at 280?increases from 4.3 of NiO NWs sensor to 15.1 of(Fe₂O₃)_0.016NiO NWs sensor and 55.8 of(Fe₂O₃)_0.027NiO NWs sensor.Therefore,the introduction of?-Fe2O3nanoparticles can effectively improve the gas sensing performance of NiO NWS sensor by the formation of high specific surface area and interface effect from p-n heterojunction.(3)Mesoporous hematite bunched nanowires(?-Fe2O3 BNWs)was prepared by nanocasting method with different valence metal cations doping,which using ordered straight channel mesoporous SBA-15 as hard template.Furthermore,the influence of heterovalent doping?-Fe2O3 BNWs on the gas sensing performance of ethanol gas was discussed systematically.All test results show that the sensitivity of the gas sensing material increases from 10.046 of Fe1.896Zn0.104O2.948 BNW sensor to 31.035 of Fe1.929In0.061O3.000 BNWs sensor,35.217 of Fe2.000O3.000 BNWs sensor and 45.556 of Fe1.938Sn0.062O3.031 BNWs sensor with the increase of valence.Therefore,high valence metal doping can improve the gas sensing performance of?-Fe2O3 BNWs sensor.