Fabrication Of The ZnO Nanostructures And Its Photocatalytic,Photoelectrocatalytic Properties

In recent years, photocatalytic degradation process with the metal oxide semiconductor nanomaterials has been widely concerned and explored in the wastewater treatment, for high degradation efficiency, good stability, ease of synthesis, and the non-toxic and environment-friendly characters, etc. Among the metal-oxide semiconductor materials, ZnO, as an n-type direct wide-band gap semiconductor, has been proved to have a higher photocatalytic activity under UV conditions. However, the recombination rate of its photogenerated carrier is high,reducing its degradation efficiency, and it is difficult to recover and re-reuse the catalyst. These are still the existing problems of ZnO nanomaterials in the application.Based on this, the ZnO nanomaterials are synthesized on the metallic substrate as anode, a photoelectric catalytic system is constituted. And their photocatalytic and photoelectric catalytic properties is explored. The catalytic mechanisms and effect of experimental parameters are discussed. The main results are as follows:First, a chemical solution method was used to prepare the ZnO nanorod arrays on the Ag rods substrate, which the arrays were perpendicular approximately. The ZnO nanorod arrays are produced in three growing solution with different ammonia content respectively, and the resulting samples are in the hexagonal structure, with a diameter of about 300 nm ~ 400 nm and the band gap of about 3.1eV. Among them,the degrading efficiency of the sample from the growing solution with 4ml ammonia content is highest for Rhodamine B. The PL spectra show that the oxygen vacancy concentration of this sample is higher than the other two samples, and a high concentration of oxygen vacancies could lead to a high photocatalytic activity of the sample.The photoelectrocatalytic properties of this sample are studied for Rhodamine B,the optimized experimental conditions are obtained. Under this condition, the photoelectrocatalytic efficiency of ZnO nanorod arrays is highest, about 38%, which is twice that of photocatalysis. The applied electric field improved catalytic efficiency effectively.Second, in the same methods and the experimental conditions, the wurtzite ZnO nanosheets are synthesized on the Al foil. The nanosheets are substantially perpendicular to the substrate with a thickness of about 200 nm. Under the optimized conditions, the photocatalytic efficiency of the ZnO nanosheets is 36% for Rhodamine B, while the photoelectrocatalytic efficiency is only 24%. The photocatalytic efficiency of the equal quantity ZnO nanorod arrays is about 33%,while the photoelectrocatalytic efficiency is increased to 61% under the electric field.ZnO nanosheet structures have higher ratio of the exposed polar surface than ZnO nanorod arrays, resulting in the higher photocatalytic efficiency than the ZnO nanorod arrays. The photocatalytic efficiency of ZnO nanosheets is reduced, which could be attributed to the morphology and substrate of the nanosheets.