Effect Of Organic Additives On Electrochemical Performance And Electrodeposition Process Of Titanium-based Lead Dioxide Electrode

The new-type titanium-based lead dioxide anodes for electrolytic zinc possess some advantages like high corrosion resistance and better electrocatalytic ability,however,they can not be industrialized yet owing some serious flaws on the surfaces and the weak binding force of coating.In order to solve this problem,the organic additives AEO-7 and PEG 6000 were added into the nitrate solution respectively,and the Ti-PbO2 anodes,which showed stronger binding force and better quality of coating,were prepared in these solutions by direct current electrodeposition method and characterized by physical methods.The effects of organic additives on electrochemical properties of anodes were studied in model system of electrolytic zinc;Moreover,the Pb02 electrodeposition behavior,fundamental Kinetics feature and the kinetics process of Pb02 electrocrystallization were discussed in the nitrate solutions,as well the influences of organic additives on these process.The specific results are as following:The effects of the organic addition agents on PbO2 phase composition and morphology were studied by XRD and SEM,and the influences on electrochemical performance of anodes were researched by anode polarization curves,Tafel curves and Electrochemical impedance spectroscopy.The results show that the crystal form of ?-PbO2 had no change in presence of organic addition agents,but the preferred growth was observed;The growth of PbO2 grains followed the Generalized Electrochemical Aggregative Growth Mechanism,and the plating defects disappeared when organic addition agents existed in the solution,besides,the grains were refined;As the result of electrolysis testing in ZnSO4 solution,the Ti-Pb02 anodes showed lower oxygen evolution potential and better corrosion resistance in presence of organic addition agents,nevertheless,their electrocatalytic activity was declining.The effects of organic addition agents on PbO2 electrodeposition process were studied by cyclic voltammetry and linear sweep voltammetry,and the results indicated that the PbO2 electrodeposition process was diffusion-irreversible-controlled,in addition,the nucleation process of PbO2 was only occurred at the surface of substrates whether the additives were existing or not,but the additive changed the overpotential of PbO2 nucleation;The further electrodeposition of Pb02 was promoted by the PbO2 layer which had electrodeposited earlier due to its catalytic performance,and AEO-7 restrained this property,on the contrary,PEG 6000 reinforced this catalytic effect.The PbO2 electrocrystallization process on diffusion controlled was researched by chronoamperometry,SH mathematic model and other kinetic theories,as well expound the effects of organic addition agents on the kinetics process of PbO2 nucleation.It turned out that the PbO2 electrocrystallization was affected by overpotential.Higher overpotential meant the faster rate of PbO2 nucleation and greater number density of nucleation active sites.The diffusion coefficient of Pb2+ was increased as the step potential shifted towards positive owing the change of solution viscosity,electromigration and the interference of oxygen evolution.Moreover,the organic addition agents were in favour of Pb2+diffusion;The PbO2 followed 3D progressive nucleation mechanism in based solution,and AEO-7 won't change this course,but the nucleation mechanism of PbO2 turned to be instantaneous nucleation in the presence of PEG 6000;Although,both AEO-7 and PEG 6000 can increased the quantity of electrodeposition PbO2 on subtrates,the mechanism of actions of them were different.