Controlled Synthesis And Gas Sensing Properties Of Ordered Mesoporous Ga-based Semiconductor Materials

There are many kinds of gas sensors,which are widely used in the fields of daily production,energy exploration,ecological protection and medical diagnosis.Metal-oxide-semiconductor sensors have attracted a lot of attention due to their excellent characteristics in terms of sensitivity,response-recovery time,operating temperature,selectivity,lower detection limit,and stability,their core key is the development of efficient gas-sensing materials.Ga-based composite oxide semiconductor is a promising gas-sensitive material due to its structural stability and easy-to-control features.The ordered mesoporous structure of gallium-based oxide semiconductors has a large specific surface area to provide more active sites for the catalytic reaction,and larger pore size is more conducive to the transport of gas molecules,which can better enhance the gas sensing performance.This thesis used ordered mesoporous silica KIT-6 as a hard template to synthesize a series of ordered mesoporous gallium-based composite oxide semiconductors and explored its application in the detection of harmful gases such as acetone and p-xylene for the first time,and the structure-activity relationship between the material structure and the gas sensing performance was studied,and the remarkable effect of enhancing the gas sensing performance was achieved.1.A series of ordered mesoporous CuGa2O4-X(X=40,80,100,130,140)were synthesized using KIT-6 as a hard template.As the hydrothermal temperature of the template decreases,the gradual increase of the specific surface area(from 80 m2 to 150 m2)and pore size(from 3.5 nm to 11.6 nm)of the material CuGa2O4,the gas sensing properties are also gradually enhanced.The gas-sensing performance test of the material found that CuGa2O4-40 has a high response to acetone gas of 1 ppm at the optimal operating temperature of 220℃(sensitivity Rair/Rgas=6.2),a lower detection limit of 2 ppb(sensitivity Rair/Rgas=1.26),and it also has a good stability.2.A series of ordered mesoporous NiGa2O4-X with different mesoscopic structures(X=100,130,140)were also synthesized using KIT-6 as a hard template.With the gradual increase of the specific surface area and pore size of the material,the gas sensing properties are also gradually enhanced.Among them,the NiGa2O4-100 has a higher response to p-xylene gas of 1 ppm at the optimal operating temperature of 340℃(sensitivity Rgas/Rair=9.1)and a lower detection limit of 2 ppb(sensitivity Rgas/Rair=1.19),it also has a good stability.3.A series of mesoporous NiGa2O4-NiO-Y(Y=10%,20%,40%,80%)with different filling ratios were synthesized by the method of nano-casting and secondary filling.The specific surface area of the composites was above 125 m2,and the pore size was mainly concentrated in large mesoporous(about 11.6 nm).The experimental study found that when the secondary filling ratio of NiO is 20%and the optimal operating temperature is 280℃,the performance detection of 1ppm p-xylene gas reaches the best state(sensitivity Rgas/Rair=75.8),a lower detection limit of 2 ppb(sensitivity Rgas/Rair=1.4),and it also has a good stability.Compared with pure phase mesoporous NiGa2O4,the optimal working temperature of the composite NiGa2O4-NiO-20%was reduced from 340℃ to 280℃,and the sensitivity to p-xylene gas of 1 ppm is 13 times higher than before(from 5.37 to 75.8).