Acetone Gas Sensors With High Anti-Humidity Properties Based On NiO Gas Material

With the rapid development of digitization and information technology,sensors,as the main method and means of sensing and collecting information,have become the basis of modern production and are indispensable in people's life.The gas sensor based on metal oxide semiconductor(MOS)has been widely concerned by researchers because of its advantages such as moderate price,high reliability,low power consumption and simple operation.Although MOS-based gas sensors have many outstanding advantages,the influence of humidity on MOS-based gas sensors remains a huge challenge to further expand their application fields.Generally speaking,the p-type oxide semiconductor has high oxygen adsorption capacity and good stability under high humidity conditions,which can be used to design a gas sensor with high moisture resistance.However,due to the limitation of its conduction mode,the sensitivity and selectivity of p-type oxide semiconductors are generally lower than that of n-type oxide semiconductors.Therefore,the modification of p-type oxide semiconductor has become very significant.Therefore,in this paper,the representative p-type oxide semiconductor material NiO was modified by doping with different valent metal ions and constructing heterojunction to construct a gas sensor with high humidity resistance and high sensitivity.The specific research contents of this paper are as follows:NiO materials with flower-like microsphere structure were synthesized by hydrothermal method and modified by adding different proportions of Ru³⁺into NiO.NiO samples with different Ru³⁺doping ratios were characterized and gas sensitive properties were tested.The test results show that the NiO material doped with 0.5 at%Ru has the best gas sensitive properties.Its sensitivity for acetone gas at 100 ppm is 12.56,about 10 times that of the gas sensor based on pure NiO flower-like microspheres.And its selectivity to acetone gas is also improved.In addition,under different humidity conditions,the baseline resistance and the response value of the gas sensor to acetone gas remain basically unchanged,providing excellent anti-humidity properties.The change of carrier concentration in NiO,the increase of relative percentages of Oc and Ov and the catalytic effect of Ru are the reasons for the improvement of gas sensitivity of the sensor.Besides,due to the incorporation of Ru³⁺,the surface of the sensitive material is rich in defect states,which is the reason for the anti-humidity properties of the sensor.Due to the strong oxygen adsorption capacity of NiO,it has a certain moisture resistance,combined with the ability of regulating carrier concentration of heterojunction.We synthesized NiO/NiFe₂O₄composite materials with different Ni/Fe ratios by co-precipitation method.It is found that the morphology of NiO/NiFe₂O₄composite is nano cube,and the size of each cube is about 70 nm,which has good uniformity and dispersion.According to the gas sensitivity test results,the NiO/NiFe₂O₄composite with a Ni/Fe ratio of 1.5 has the best gas sensitivity to acetone gas,with a sensitivity of 20.1?100 ppm,a lower response-recovery time(2s and 3s)and a lower detection limit of 200 ppb,and still has good stability under high humidity conditions.According to the analysis of material structure and gas sensitive characteristics,one of the important cause of the improvement of gas sensitive characteristics of gas sensor is the large specific surface area of NiO/NiFe₂O₄with a Ni/Fe ratio of 1.5,the formation of p-p heterojunction and the catalytic ability of NiFe₂O₄materials to acetone gas.