Preparation Of Metal Oxide Electrode And Its Application In Chemical Oxygen Demand Detection

Chemical oxygen demand（COD）is an important index to evaluate the degree of water pollution.Traditional COD detection uses permanganate or dichromate oxidation.The principle is that under certain conditions,reducing substances in water are oxidized by strong oxidants,and the oxygen concentration corresponding to the oxidant consumed is mg/L.This method has some serious drawbacks,such as large equipment,long time,use of toxic and harmful substances,and the reproducibility of the results is not very high depending on the skill of the operator.Electrochemical detection of COD can effectively avoid the above shortcomings,and electrode selection plays an important role in electrochemical detection of COD.Based on the existing problems,three kinds of electrodes are prepared for the determination of COD value of organic matter in water.The main research contents are as follows:1.TiO₂ nanorods were prepared by hydrothermal method on FTO,and PbO₂was prepared by electrodeposition to obtain the FTO/TiO₂/PbO₂electrode.TiO₂nanorods provide 3D structure,greatly increase the electrode area,provide more active sites to improve the production of·OH,more conducive to the electrocatalytic oxidation of organic matter,and enhance the adhesion of PbO₂layer,so that the electrode is not easy to fall off.The effects of working potential,electrolyte concentration and rotational speed on the test results were studied.The electrodes were characterized by scanning electron microscopy（SEM）,X-ray diffractometry（XRD）,linear scanning voltammetry（LSV）and·OH formation ability detection.Under the optimal experimental conditions,the COD values of five different types of organic matter were detected,and the sensitivity and linear range of each organic matter electrode detection were different.Meanwhile,the effect of Cl^-on COD detection and the accuracy of electrode are studied.The relative deviation is between2.90%and 10.59%.FTO/TiO₂/PbO₂electrode can be used in the electrochemical detection of COD.2.Cu/CuO electrodes were prepared by cyclic voltammetry（CV）in NaOH solution.The preparation method is simple,with high repeatability and ideal electrode performance.The detection sensitivity,linear range and detection limit of COD values of six kinds of organic compounds were determined under the experimental conditions of optimized working potential and electrolyte concentration.Standard samples with different COD values are analyzed by Cu/CuO electrode and K₂Cr₂O₇method.The linear equation is as follows:COD_Cr=0.9052 COD_Ec-1.2731.The relative standard deviation of COD value between the electrode and K₂Cr₂O₇method is 4.21%～16.30%.The Cu/CuO electrode is as accurate as the traditional method,and at the same time is cheaper and more environmentally friendly,so it can be used in practical applications.3.Cu/CuO electrode and Cu/CuO-MCT electrode were obtained by adding commercial nano-CuO and carboxylated multi-walled carbon nanotubes（MCT）to N,N-dimethylformamide in a mass concentration ratio of 5:1 to form a suspension.The electrode performance was studied by comparing the net response current of glycine with the same COD value electrolyzed by different electrodes.Cu/CuO-MCT electrode was selected as the working electrode to detect COD values of seven organic compounds under optimized detection conditions.