Controllable Preparation Of Micro/Nano Cu₂O And Its Visible Light Photocatalytic Performance

Cu2O is a direct bandgap semiconductor material semiconductor, which have significantly potential applications in solor cell, electrode material of lithium ion battery, sensor and photocatalytic material. Compared with traditional photocatalyst, Cu2 O have visible light driven photocatalytic activity as to its higher visible light absorbance. This thesis focuses on the controllable preparation of Cu2 O materials through different synthesis methods and their photocatalytic performance under visible light irradiation.1 Cu2 O particles, nanowires and hollow spheres were successfully synthesized using solution reduction, hydrothermal and soft template methods. Five different shapes of uniform and monodispersed Cu2 O particles were prepared under different temperatures and solvent system by using solution reduction method, including sub-micro truncated octahedron, tetrakaidecahedron, cubic, octahedron crystals and nanoparticles with 50 nm in diameter. Through hydrothermal method, high aspect radio Cu2 O nanowires were synthesized. The diameter of the nanowire is around 80~200 nm. SDS and bubbles were utilized as the soft template to synthesis two types of hollow structured Cu2 O microspheres. The size of the microspheres prepared by SDS template method is about 200~500 nm, which is smaller than that of bubble template method(500~800 nm). The wall thicknesses of the hollow microspheres prepared by SDS template and bubble template are 100 nm and 20~50 nm respectively.2 The optical properties of Cu2 O samples rely on their morphologies and sizes. The sub-micro Cu2 O crystals have similar optical absorbance properties and the band gaps calculated from the UV-Vis absorbance spectrumare are in the range of 2.13 to 2.15 eV. But, the nanoparticles show a redshift phenomenon, the value of the band gap is 1.80 eV. The band gap of nanowires is 2.05 eV and the two types of hollow spheres prepared by SDS and bubble template are 2.22 eV and 1.90 eV. The band gap is reduced as the grain size(calculated from XRD patern) decrease.3 The photocatalytic activity was analyzed by using methyl orange(MO) as a model pollutant molecule. The result shows that the hollow microspheres own the highest photocatalytic activity under visible light irradiation. The degradation of MO reaches 95% when using the hollow microsphere prepared by bubble template as the photocatalyst. However, the sub-micro crystals have no obvious light catalytic activity. The activities of nanowires and nanoparticles are between the sub-micro crystals and hollow microspheres. The photocatalytic activity has a strong relationship with the grain size: Generally, The smaller of the grain size, the narrower of the band gap and the better visible light photocatalytic activity. Meanwhile, the visible light photocatalytic activity also exist a positive correlation with the adsorption properties.