Abstract:
The study aimed to improve and develop the tungsten oxide thin film fabrication on composited thin films of tungsten oxide (WO3) and bismuth vanadate (BiVO4) electrode for enhancing the efficiency of the photoelectrocatalytic oxidation reaction. The experiment was conducted into three trials; the improvement of tungsten oxide thin film fabrication on the electrode by the sputtering technique and followed by the bismuth vanadate thin film layers with a spin coating technique, respectively. The influences of the tungsten oxide thin film structure and the shape on the photoelectrocatalytic properties were studied in the pattern of the dense and the nanorod tungsten oxide films. The effect of the thickness of the tungsten oxide film on photoelectrocatalytic oxidation process property was investigated for the best conditions. The morphology of the prepared electrode was characterized by using the Field Emission Scanning Electron Microscopy (FE-SEM). The crystalline structure of composited electrode was studied by the X-ray diffractometry (XRD). The elemental composition and oxidation number were confirmed by the X-ray photoelectron spectroscopy (XPS). The electrochemical resistance properties at the interfacial of electrode surface were investigated by the electro impedance spectroscopy (EIS). The optical properties were studied by the UV-Vis spectroscopy.
Secondly, the application of the developed electrode for the oxidation reaction of sodium hypochlorite production was studied and even the effects of the applied potential in the system, the concentration of the substrate, the intensity of the light and the mechanism of the catalytic function at the electrode surface on the sodium hypochlorite production efficiency were studied. The efficiency of sodium hypochlorite production of the developed sputtering WO3 and the traditional spin coating WO3 electrodes were compared. The developed electrode can produce 2,900 mg / L for sodium hypochlorite per an hour at 2.5 V (vs. Ag/AgCl) in an initial concentration of sodium chloride and a light intensity of 2.0 M and 7.3 mW/cm2, respectively.
Thirdly, the application of the developed electrode for the organic dyes removal was studied by using rhodamine B as the organic dye wastewater. The effects of the electrical potential, the light intensity, the electrolyte solution, pH, the catalytic mechanism at the electrode surface on the efficiency of organic dyes removal were investigated and compared with the traditional electrodes. The developed electrodes can degrade off the dye color to 97% per an hour with the removal rate of 0.261 per minute under 1.0 V (vs. Ag/AgCl), and the light intensity of 7.3 mW/cm2 and the aqueous sodium chloride solution at pH = 3. Both studies achieve the highest oxidation efficiency under the catalytic of bias potential and the light irradiation in the name of the photoelectrocatalytic process. The efficiency of the developed electrodes is significantly improved over conventional electrodes. It is shown that the developed tungsten oxide fabrication on the WO3/BiVO4 composite film has reached to the success in preparing the anode electrode to enhance the oxidation efficiency under the photoelectrocatalytic process. It is suitable to pursue advance studies for further development and even the applications of the sodium hypochlorite production and the removal of organic dyes in the industrial system in advance.