Investigation on the Cu(II) and Co(II) Electrochemical Reduction Process in Citrate Solution by CV and EIS

Abstract

Investigation on the Cu(II) and Co(II) electrochemical reduction kinetics in citrate solution provides important theoretical guidance for the preparation of Cu-Co alloy materials. Kinetics of Cu(II) and Co(II) co-electrodeposition in citrate solution was investigated by Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS). To bring the reduction potentials of Cu(II) and Co(II) closer, various citrate concentrations, pH values, cobalt concentrations and copper concentrations were studied. Preliminary study on the molecular structure of the complexes was performed by Fourier transform infra-red spectra (FT-IR). Results show that the reduction potentials of Cu(II) and Co(II) is close in solutions comprised of 0.05∼0.15 M CuSO4·5H2O, 0.05 M CoSO4·7H2O, 0.20 M C6H5Na3O7·2H2O, 0.20 M Na2SO4 or 0.05 M CuSO4·5H2O 0.05∼0.20 M CoSO4·7H2O, 0.20 M C6H5Na3O7·2H2O, 0.20 M Na2SO4 with pH at about 6. The Cu(II)-citrate and Co(II)-citrate are first reduced to an intermediate state and then to Cu0 and Co0. Adsorption exists at the surface of the electrode. The complex is multidentate because ring formed indicating by IR.