Photoelectrocatalytic Treatment Of Nitrogen-containing Organic Pollutants Using Electrodeposited ZnO Thin-film Electrode

Photoelectrocatalysis (PEC) is a combination technique of photocatalysis and electrochemistry. In this technique, photogennerated electrons in the photocatalytic process can be transferred to the external circuit by the application of external bias potential. Thus the recombination of photoelectrons with the holes is inhibited and the photoelectrocatalytic efficiency is improved. In this thesis, we prepared a ZnO film to study the PEC degradation of nitrogen-containing organic pollutants. The main contents were described as follows.(1) We deposited ZnO thin film on a glassy carbon surface via the electrochemical deposition method. The photoelectrochemical properties, surface morphology and structure of the deposited ZnO thin film were characterized with various modern physicochemical methods including photocurrent response, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and X-ray diffraction (XRD).(2) The PEC degradation of p-nitrophenol (PNP) over the ZnO film was studied. The results demonstrated that 2h PEC degradation efficiency for 0.05 mmol/L PNP reached up to 98.8% under the following conditions: external bias potential of 1.0 V, supporting electrolyte (Na2SO4) concentration of 0.1 mol/L, natural pH(pH=6.3).(3) The PEC degradation of benzotriazole (BTA) over the ZnO film was studied. The results showed that 3h PEC degradation efficiency was 74.8% after treating for 0.2 mmol/L BTA in 0.1 mol/L Na2SO4 by applying an external bias potential of 0.8 V.(4) The PEC degradation of aminopyrine over the ZnO film was studied. The result showed that the PEC technology did not shown obvious advantages for treating aminopyrine. In comparison, in the presence of potassium persulfate (K2S2O8), aminopyrine could be effectively degraded by the method of K2S2O8+UV. The degradation rate of aminopyrine was improved with the increase of K2S2O8 concentration. Under optimal conditions, namely 0.1 mol/L Na2SO4, natural solution pH and 1 mmol/L K2S2O8, the 1-h photodegradation efficiency for 0.1 mmol/L aminopyrine reached up to 91.8%.