Meihua Yu

Controllable fabrication of nanostructured copper compound on a Cu substrate by a one-step route

We report a one-step corrosion process to synthesize nanostructured CuO thin films at room temperature. The reaction time has great effect on the composition and microstructure of products to control the size and shape of the copper compound. X-ray diffraction studies showed the transformation of nanograins from Cu(OH)2 nanowires to flower-like CuO and to dispersed CuO nanosheets. The optical properties of CuO nanosheets were investigated by using UV-vis spectroscopy with considerable blue-shift in the optical band gap (Eg = 1.8 eV) due to the quantum confinement effect. Additionally, the photocatalytic activities of as-prepared copper compound films were determined by measuring the degradation of methyl blue (MB) to find out their potential application in waste water treatment. The photoluminescence (PL) spectrum showed both UV as well as visible emission peaks, indicating their good optical properties. Moreover, a reasonable growth mechanism for the formation of the CuO nanostructure is proposed by means of a scanning electron microscope (FESEM).

Enhanced visible light photocatalytic performances of self-assembled hierarchically structured BiVO4/Bi2WO6 heterojunction composites with different morphologies

Novel self-assembled hierarchical BiVO4/Bi2WO6 heterostructured composites with different morphologies were controllably synthesized via a facile and template-free solvothermal method. The effects of the molar ratio of V to W on the structure, morphology, photocatalytic activity and photoelectrochemical properties of the BiVO4/Bi2WO6 composite photocatalysts were investigated in detail. The results showed that all the BiVO4/Bi2WO6 composites exhibited much better photocatalytic activities for methylene blue (MB) degradation and photoelectrochemical performances than pure BiVO4 and Bi2WO6. Among the composites, the BiVO4/Bi2WO6 microsphere with the molar ratio of V to W of 2 : 1 exhibited the best photocatalytic performance. The mechanism of enhanced activity was systematically investigated by UV-vis diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy, and photo-electrochemical methods including transient photocurrent responses, electrochemical impedance spectroscopy (EIS) and Mott–Schottky plots. The enhanced photocatalytic activity could be ascribed to the tetragonal–monoclinic heterophase structure, high surface oxygen vacancy concentration, narrow band gap energy and mainly the formed heterojunction structure which could effectively promote the separation of photogenerated electron–hole pairs. In addition, a possible photocatalytic mechanism for the enhanced photocatalytic activity was proposed on the basis of the calculated energy band positions of BiVO4 and Bi2WO6.