Synthesis Of Indium Oxide Composite Materials And Its Gas Sensing Studies

Gas sensor is an effective technique to realize the real-time detection of volatile organic compounds(VOCs).Indium oxide(In2O3)has become one of the most potential sensing materials as its good stability and strong gas sensing properities.The design of p-n heterojunction composites can improve the amount of chemisorbed oxygen and the electrical properties,so it has become one of the important ways to improve the sensitivity and selectivity of gas sensing.In addition,the complexity of the relationships among morphology,structure and properties of heterojunction materials poses a challenge to the research of gas sensing mechanism.In this work,taking advantage of the surface and catalytic characteristics of p-type cobalt trioxide(Co3O4),two different Co3O4-In2O3 heterojunction materials were synthesized based on In2O3 host material through the two-step hydrothermal method and physical mixed calcination method.The gas sensing performance and the mechanism of sensitivity enhancement were systematically studied.The detailed contents are as follows:1.Co3O4-In2O3 heterojunction materials(CIO)with different Co/In ratios were prepared by a two-step hydrothermal method,and the response to ethanol gas was systematically studied.The response of 6%Co3O4-In2O3(CIO-6)material to 100 ppm ethanol at 280?(541±16)was 3.9 times that of the pure In2O3 sample.A series of spectrum and electrical analysis results proved that the surface modification of Co3O4 make In2O3 had more surface defects,lower band gap,bigger specific surface area and electron mobility due to the heterojunction effect,thereby effectively improving the gas sensitivity.2.Co3O4 modified In2O3(ZIO)samples were synthesized by mixing In2O3 with ZIF-67 and then calcined at 300?.The properities of gas sensing to ethanol were also studied.The response of ZIO-6 to 100 ppm ethanol at 280?(5585±352)was about 39 times that of the pure In2O3.Through the analysis of surface elemental state,optical properties and electrical properties of materials,it was found that surface modification ZIF-67/Co3O4 could effectively reduce the band gap,increase electron mobility and chemisorbed oxygen of material.At the same time,the resistance ratio in two atmospheres was effectively increased by the design of the p-n heterojunction structure,thereby a rapid improvement in gas sensing performance was achieved.By comparing the catalytic properties,electrical properties and morphological characteristics of ZIO and CIO materials,the reasons for the differences in gas-sensing properties of the two materials were investigated.