Study On The Gas Sensing Properties Of Nickel Oxide-based Doping And Heterostructure

Metal oxide semiconductor gas sensor can effectively detect most of the toxic and harmful gases.Sensitive materials are the core of metal oxide semiconductor gas sensor,so it is particularly important to develop high-performance sensing materials for the development of metal oxide semiconductor gas sensor.Nickel oxide(NiO)is p-type metal oxide semiconductor material with high catalytic activity,and existis a large amount of chemisorbed oxygen on its surface,which is conducive to design the gas sensors with anti-interference as well as rapid response and recovery rate.In practical application,the NiO based sensor generally shows a low gas-sensitive response value because of the special conduction mode of p-type semiconductor,which limits their application.According to NiO has good electrical conductivity,its electron sensitization can promote through the doping and constructing heterojunction then improve the response value and selectivity.Therefore,we have synthesized the different ion doped NiO and heterostructures with large specific surface area and porous properties using the metal-organic framework as template.The sensors achieve the high sensitivity and rapid detection to triethylamine and xylene,the sensitization mechanism is further studied.The specific research contents are as follows:1.The NiO and Ga-doped NiO dendrite porous structures are synthesized by metal-organic framework template.The gas sensitivity tests show that the response value of the 3 at%Ga-NiO based sensor to 50 ppm triethylamine is 21.6 at the optimal operating temperature,which is 14 times higher than that undoped NiO based sensor,shows fast response/recovery speed(2 s/6 s)and good stability.Ga³⁺ion doping causes the holes concentration in NiO decrease,oxygen vacancy content and the specific surface area increase,which are the key factors for the improvement of gas-sensitive response value.The porous dendrite structure can provide more channels for the diffusion of gas molecules and realize the rapid detection to triethylamine.2.The NiO and Fe-doped NiO nanosheets hierarchical structure are designed and fabricated.The effect of surfactants and reaction time on the microstructure are studied,and the growth mechanism is proposed according to the nucleation self-assembly mechanism.The gas sensitivity tests show that the response value of0.52 at%Fe-NiO based sensor to 50 ppm triethylamine is 64 at the optimal operating temperature,which is 21 times higher than that undoped NiO based sensor,shows fast response and recovery time.The enhanced response value is related to the rapid reversible valence change between Fe³⁺and Fe²⁺ions,and the increase of surface vacancy content caused by doping.3.Polyhedral NiO and NiMoO₄-NiO heterostructures are designed and fabricated.The effect of surfactant on the microstructure is studied,and the growth mechanism of polyhedral structure is clarified according to the characteristics of coordination extension of metal-organic framework.The gas sensitivity tests show that the response value of 5 wt%NiMoO₄-NiO based sensor to 50 ppm triethylamine is 150 at the optimal operating temperature,which is 57.7 times higher than the pure NiO based sensor,and 10 times higher than that of other interfering gases,shows excellent selectivity and improved the response recovery rate.The holes concentration in NiO decreased caused by forming NiMoO₄-NiO heterostructure and the introduction of Mo⁶⁺enhances the catalytic effect to triethylamine gas.So,the response value and selectivity to triethylamine are improved.4.Rod NiO and Ni WO₄-NiO heterostructures are synthesized by metal-organic framework template.The effects of the operating temperature on gas selectivity are studied.Gas sensitivity tests show that the response value of 12 wt%Ni WO₄-NiO based sensor is 65 to 50 ppm triethylamine at 240?,which is 3 times than that of 50ppm xylene.At 270?,the response value to 50 ppm xylene is 28,which is 2.8 times higher than that of 50 ppm triethylamine,realized the double detection of two gases at different working temperatures.Operating temperature affects redox activity and the selective catalysis to different functional groups are the reasons for obtaining the dual detection performance.