Effect Of Some Additives On Zinc Electrodeposition Studied By CV And EQCM

Electrochemical quartz crystal microbalance(EQCM)is a novel and much more sensitive apparatus that permits the measurement of mass variations(in the range of nanogram)that occur at an electrode surface.It takes the advantages of simple structurethe,high sensitivity,good specificity,high resolution and cheap price.It can simultaneously measure the changes of surface mass,quantity of charge and current in a potential scan,revealing more details for the electrochemical fuctions of the ion/molecular on the electrode surface.Recently the EQCM technique has become a widely used technique in several areas of electrochemistry,electroanalytical chemistry,bioelectrochemistry,etc.The main studies carried out in this dissertation are summarized as follows:1?In this thesis,the basic principle,construction of the electrolytic cell and experimental setup in EQCM was introduced.The application in electrodeposition,electro-adsorption on suface,metal corrosion,conducting polymers act was reviewed.At the same time,a few of disadvantages of EQCM in application are discussed.2?The deposition of zinc on Pt/Fe electrode and effect of anisaldehyde(ANI)on the processes in alkaline zincate bath were investigated by using cyclic voltammetry(CV)and electrochemical quartz crystal microbalance(EQCM).The experimental results demonstrated that one wave(at-1.42 V)was associated with the hydrogen evolution reaction(HER)on Pt/Fe electrode,while the other peak(at-1.54 V)with zinc bulk reduction.The reduction process of zinc occured under mass transfer control.The dynamics of zinc electrodeposition process was still the mass transfer control after the addition of ANI.The deposition of zinc could be inhibited by absorption of ANI on the surface of Pt/Fe electrode.The M/n values were 29.9 g/mol in the absence of 5.0 mmol/L ANI and 31.6 g/mol in the presence of 5.0 mmol/L ANI,respectively,which indicated that the mechanism of zinc electrodeposition was a 2-eletrons process.3?The influence of benzylideneacetone(BDA)and cinnamic acid(CIN)on the of Zn2+ions on Pt/Fe electrodes in acidic media was investigated by cyclic voltammetry and electrochemical quartz crystal microbalance(EQCM).Results indicate,in the presence of BDA or cinnamic acid,both the UPD and the OPD of Zn2+ could be inhibited,and the indicate effect was stronger in the potential region of the UPD of Zn in the presence of cinnamic acid,while was stronger in the potential region of the OPD in the presence of BDA.The processes of zinc electrodeposition and dissolution wre synergistically inhibited when BDA and cinnamic acid wre added simultaneously in the weak acid bath.The M/n values are 32.6 g/mol?27.1 g/mol?30.0 g/mol and 33.3 g/mol in the solution containing no additives,BDA,CIN and both respectively,which indicated the mechanism of Zn position was a 2-eletrons process.In addition,the presence of BDA or CIN in the electrolytic bath induced significant changes in the morphological characteristics of zinc coating.4.The influence of cinnamic acid on the mechanism of Zn deposition and nucleation kinetics onto glassy-carbon electrode was studied by voltammetry,chronoamperometry.The CV studies revealed that the thermodynamic process of zinc electrodeposition was not changed and the equation of zinc reduction process(Zn2+ + 2e ? Zn),was not changed in the presence of CIN,while the dynamic process was changed and the formation rate of zinc nuclei was accelerated.Analysis of chronoamperometry indicated that,in absence of CIN,zinc deposition was consistent with the model of 3D-instantaneous diffusion-controlled nucleation,while was consistent with the model of 3D-progressive diffusion-controlled nucleation.The addition of CIN caused a reduction in the nucleation rate constant(A)and a increase in the number density of active sites(N0)with respect to the values obtained without CIN.