Preparation Of ZnO Nanomaterials And Photoelectrochemical Performance

Zinc oxide （ZnO） is one of the most important multifunctional semiconductormaterials, which has great application prospect in photoelectrocatalyst, solar cells, gassensors, nano generators owing to its outstanding optical and electrical properties. ZnOnanomaterials have excellent photoelectrocatalysis performance for the degradation ofrefractory organic pollutants due to their small particle size and large specific surfacearea. In recent years, as environmental protection and the growing pollution problems,scientists have paid great attention to the study of environmentally friendly materials.ZnO nanomaterials have attracted much research interest for their several advantagessuch as high efficient, non-toxic, low cost and have great potential in management andprotection of environmental. In this study, morphology controllable ZnO nanomaterialswere prepared by electrochemical deposition technique and investigated theirphotoelectrocatalysis performance. The samples have been characterized by usingScanning Electron Microscopy（SEM）， X-ray diffraction（XRD） and UV–VISspectrophotometry.ZnO nanorod arrays have been successfully prepared on the ITO substrates byelectrochemical deposition technique using zinc nitrate and hexamethylene tetramine aselectrolyte. Cyclic voltammetry experiments were performed to determine the range ofthe deposition potential. The results showed that the deposition potential was in a rangeof-0.8^-1.2V and the optimum deposition parameter to be-1V. Nano-columnarstructures of ZnO were prepared under various potential from-0.8to-1.0V. With theincrease of deposition potentials the density of the column-like strctures increases andthe average diameter changes from260nm to320nm. ZnO seed layer grown by Sol-geldip coating method can significantly increase the specific surface area, the densityincreases and the size decreases, the average diameter can be37nm.Increasing the concentration of zinc nitrate electrolyte can increase the specificsurface area of nano-ZnO, XRD results showed that ZnO nanoparticles along the c-axispreferred orientation is also increasing. The additional support electrolytes have apronounced effect on the morphologies of ZnO. We found that addition of KNO₃support electrolyte can promote the growth of ZnO, C₆H₁₂N₄can promote columnargrowth of ZnO and KCl would inhibit the growth of ZnO along the <0001> direction.ZnO nano-column turned into the large size of sheet-like structures when addingNa₂SO₄support electrolyte.The efects of the morphologies of nano-ZnO on photoelectrocatalysis propertieshave been reported. To control the shape, several kinds of supporting electrolyte such as KNO₃、C₆H₁₂N₄、KCl、Na₂SO₄were added to the zinc nitrate aqueous solutions.Different morphologies of ZnO have been successfully synthesised and used as theanode catalyst under1voltage for the degradation of methyl orange with an initialconcentration of10ml. The results showed that both the nanorods which were obtainedby adding C₆H₁₂N₄solution and the sheet-like structures of ZnO which were obtainedby adding Na₂SO₄solution exhibited the good photoelectrocatalysis degradationperformance. Methyl orange effluent was decolorized by92%within2h. This wasmainly attributed to a large specific surface area of ZnO and the interleaved structuresof nano-ZnO formed many voids, which can improve their adsorption of methyl orange,making the degradation rate higher. Further, the two polar crystal planes of thesheet-like structure of ZnO be exposed to pollutants which was conducived to chargeexchange, thereby, the catalytic activity of ZnO was enhanced.