Investigation And Application Of Mesoporous Cr₂O₃-based Gas Sensors

In coal chemical production stage produce or reveal large amounts of toxic or harmful gases such as methane, carbon monoxide, hydrogen sulfide and sulfur dioxide. These gases have brought serious harm to workers and environment. In order to prevent spreading further, we need to study efficient, fast and cheap gas sensor. Mesoporous metal oxide have been used widely because of its excellent performance. Traditional semiconductor research of SnO2 or In2O3 is hot, but most researchers just stay in the initial synthesis of mesoporous metal oxide. In this article we went in a different direction, chose Cr2O3 as research subject and used hard-template method to synthesize mesoporous materials to contrast a range of mesoporous Cr2O3 with different pore size, pore structure and specific surface for formaldehyde gas responses. And by doping metal ions to change the material surface activity and surface carrier concentration to enhance the performance.1. A series of KIT-6 hard templates with different structure have been synthesized by controlling different hydrothermal temperature (40,80,100,130,140℃). By nanocasting and "Water-n-hexane" dual solvent system to synthesis different mesoporous Cr2O3 with different structural parameters. Through wide-angle XRD, small-angle XRD, EDS, N2-physical adsorption and desorption, TEM to analysis phase and structure. In nanocasting method, the order of mesoporous Cr2O3 by once filled chromium nitrate precursor lower than the second filled and all of them have low specific surface area, Cr2O3-40-60%-1 is 26 m2/g and Cr2O3-80-60%-1 is 51 m2/g. With "Water-n-hexane" dual solvent system to synthesize mesoporous Gr2O3 has a more excellent structure, the specific surface area of Cr2O3-40-60%-1-D and Cr2O3-80-60%-1-D is 87m2/g and 86 m2/g respectively. Increases the efficiency of KIT-6 apertures. Through the test of formaldehyde gas found that the best optimum operating temperature is 170℃. Then the sensitivity to 1 ppm formaldehyde of Cr2O3-40-60%-1-D reached 83.2. The surface modification to sensitive materials properties has a huge impact.By doping different kinds of metal ions(Fe3+、In3+、La3+、Ce3+) to change surface activity of mesoporous Cr2O3-100. Through characterization have discovered synthesis materials phase purity, structural integrity and orderly. After formaldehyde test found pure phase mesoporous Gr2O3 optimum operating temperature is 170℃, while doped In3+ and Fe3+, the operating temperature reduced to 150℃, which the In3+-Cr2O3-0.1 on sensitivity 1 ppm of formaldehyde gas is 399.3. By changing the material surface carrier concentration to analyze the impact of the gas sensing performance. By doping Ni2+, Sn4+and W6+ to change concentration of the carrier. A analysis of the synthesized mesoporous Cr2O3 doped metal ion found the complete structure. Test found that the sensitivity of Sn4+-Cr2O3-0.1 with the doping ratio of nsn/ncr=0.1 up to 2000 to 9 ppm formaldehyde gas, but the pure phase Cr2O3-100 only is 769, the value improved 2.6 times.