Microstructure Design,Preparation And Gas Sensing Properties Of Nano-Co₃O₄

Metal-oxide semiconductor gas sensor has advantages of high sensitivity, fast response, small size, low energy consumption and costs, and easy to operate. Metal-oxide semiconductor with special morphology and exposing special crystal face is benefical to improve gas sensing properties. In this study, different morphologies Co3O4 were prepared by hydrothermal, solvothermal and electrospinning methods. Finally, we discussed the influence of dopant metal ions and surface modifier heterojunction on morphologies, microstructure and gas sensing properties of Co3O4.Nanosheets and nanorods Co3O4 were synthesized by adopting Co(NO3)2?6H2O or Co(Ac)2?4H2O as raw material and a certain amount of surfactant through hydrothermal or solvothermal method. Co3O4 fiber was prepared by electrospinning method using Co(NO3)2?6H2O as raw materials, ethanol and DMF as solvent, and PVP as binder after sintered. The gas sensing properties of Co3O4 nanosheets is better than other morphologies. As the interatomic distance of Co2+ ions in(111) face and the amount of dangling bonds are larger. The sensitivity of Co3O4 nanosheets to 100 ppm acetone attained 2.54.The influence of dopant metal ions on microstructure and gas sensing properties of Co3O4 was discussed. The dopant Ti4+ ions and W6+ ions displaced Co2+ ions in lattice causing lattice distortion but didn't create new phase nor disdruct the orientation of nanosheets. The sensitivity of 1mol% W-doped Co3O4 nanosheets to 1000 ppm acetone attained 5.06. As the doping concentration is moderate, 1mol% W-doped Co3O4 nanosheets had a big change in hole accumulation layer resistance and more dangling bonds, this sample exhibited best acetone sensing properties.In this study, we used ZnO modifying Co3O4 nanosheets. Zn O and Co3O4 formed ZnCo2O4 phase during heat treatment. When ZnCo2O4 and Co3O4 formed p-p heterojunction, band of the p type semiconductor bended and built-in electric field formed, while the width of the gap increases. As a result, the sensitivity increased. The influence of interaction of dopant metal ions and heterojunction modifier on gas sensing properties of Co3O4 was discussed. The properties deteriorated for Zn2+ ions diluting the effect of high valence W6+ ions and the interaction of two kinds of heterojunction. The above work provides experimental basis and theoretical reference for the research of p-type semiconductor gas sensing materials.