Study About CO Gas Sensor Based On Metal Semiconductor Oxides Via Electrospinning Method

CO is a colorless,odorless,flammable,explosive and toxic gas.CO can rapidly combine with hemoglobin in human blood and seriously interfere with the transport of oxygen to human tissues.Cardio-cerebrovascular patients who live in a certain concentration of CO for a long time will cause cholesterol and lipids in the blood to deposit in the blood vessels,which will aggravate the disease.However,due to the colorless and odorless characteristics of CO,it is difficult to detect,CO poisoning accidents occur from time to time,and even cause explosion in serious cases.Therefore,it is very important to develop high performance CO gas sensor with high response and low detection limit.However,the traditional metal oxide semiconductor sensor have many disadvantages when detecting CO gas,especially the relatively stable structure of CO gas,resulting in low sensitivity and high detection limit of CO sensor,which is difficult to meet the actual detection requirements.In view of this problem,this paper aims to solve the problems of low detection limit and slow response recovery of the sensor by changing the driving mode of the traditional sensor and adopting the dual-pulse driving detection method to replace the fixed working temperature;Further,a bimetallic modification method is used to improve the sensitivity of the sensor while reducing the interference of H2 to the sensor,combining the adsorption and catalytic capabilities of noble metals for CO gas.The specific work is as follows:First of all,a CO gas sensor based on Pd doped Sn O2 electrospinning material driven by double pulses was developed.The main components of the dual-pulse drive sensor are the upper computer,DC power supply,resistance meter and hexagonal ceramic tube coated with sensitive materials.Different from the traditional gas sensor working at a fixed working temperature,the dual-pulse drive makes sensitive materials generate more chemically active adsorbed oxygen ions on the surface of the material during high temperature preheating by means of high temperature preheating-low temperature rest-medium temperature test,expels the impurity gas adsorbed on the surface of the material,refreshes the surface of the material,and makes the material have higher air resistance during medium temperature test;While in the atmosphere,high temperature preheating can also refresh the material surface and reset the device.At low temperature rest,it can ensure that the target gas molecules fully penetrate into the sensitive material.At medium temperature,it can make more target gas react with the sensitive material,making the resistance value of the sensitive material in the target gas lower,thus achieving a lower detection limit and a higher response value.The research results show that the response of the CO gas sensor with high performance dual-pulse driving heating mode to 100 ppm CO is about 15.6,which is much higher than that of the traditional driving mode(3.25),and the lower detection limit of CO is also reduced from 5 ppm to 0.2 ppm.In addition,because high temperature preheating is conducive to the refreshing of the device surface,the sensor also shows good stability.This shows that the new driving method can greatly improve the sensitivity of the sensor and detect the lower detection limit of the target gas.Although pulse drive can improve the sensitivity of CO gas and lower the detection limit,H2,as the interference gas,still has serious interference on the device,and its sensitivity is even greater than the target gas CO.Based on this,the bimetallic loading method is further adopted to make full use of the catalytic ability of Pd to the target gas and the adsorption ability of Au to the target gas to improve the selectivity of the sensing device.The experimental results show that the response of In2O3 nanofibers modified by 2 at% Au and 2 at% Pd to 100 ppm CO at 180°C is the highest(21.7),and the response value is about 8.5 times that of pure In2O3 nanofibers.The detection limit of CO after co-doping of Pd and Au was as low as200 ppb,which was significantly lower than that of pure In2O3 nanofibers(6 ppm).Moreover,the selectivity of the sensor has been greatly improved,and its sensitivity to CO gas is significantly higher than that of H2.The above conclusions show that the modification of sensitive materials by using substances with strong catalytic and selective adsorption capabilities can not only effectively improve the sensitivity of the sensing device,but also greatly improve the selectivity of the device.