Design Of Three Dimensionally Ordered Macroporous In₂O₃ Sensors

Indium oxide is a typical wide band n-type semiconductor,which is widely used in the detection of poisonous and harmful gases.However,the pure In2O3 gas sensor often has high operation temperature,low response and high detection limitation.Therefore,over the years,people have been trying their best to improve the gas response through material modification.Noble metal Pd,as an efficient catalyst,can accelerate the chemical adsorption process;the doping of metallic Zn elements into the lattice of indium oxide can lead to more structural defects.Three dimensionally ordered macroporous structure has a stable structure and a higher specific surface area,thus providing more adsorption sites.In this paper,3DOM In2O3,Pd loaded 3DOM In2O3 and Zn doped 3DOM In2O3 sensors were prepared using colloidal template method.The effects of composition and structure on gas sensing performance were investigated and a series of characterization and mechanism exploration were carried out.The details are as follows:1.First,3DOM In2O3 was prepared as sensor through colloidal crystal template method and then Pd loaded 3DOM In2O3 gas sensors were fabricated using palladium chloride acid as a source of palladium and NaBH4 as a reducing agent.The sensing properties of the sensors toward NO2 were performed.The results showed that the response of 0.5wt%Pd 3DOM In2O3 to 500 ppb NO2 at room temperature was as high as 980.Compared with the pure 3DOM In2O3,the optimal operation temperature decreased by 25? and the response is almost 5 times higher than that of 3DOM In2O3.We found that the samples have stable structures and larger specific surface area,which are helpful to gas adsorption.The enhanced gas-sensing performance is due to the increased amount of electron concentration,the catalytic effect of Pd NPs and the synergistic effect of Pd NPs and In2O3 support.2.In this chapter,Zn doped 3DOM In2O3 sensors with different doping molar ratios were prepared by colloidal crystal template method,which were used for NO2 detection.We have compared the gas sensing performance between pure 3DOM In2O3 and 3DOM In2O3/Zn-2.5%.The response of 3DOM In2O3/Zn-2.5%to 50 ppb NO2 at 50? was 30,which is approximately 15 times higher than that of pure 3DOM In2O3.The characterization results showed the amount of structure defects and adsorbed oxygen have increased obviously after Zn doping,which would be helpful to capture more of the target molecule.Thus Zn doped 3DOM In2O3 showed the enhanced sensing performance.