A Rotating Ring‐Disk Electrode Investigation of Copper Electrochemistry in Polyethylene Glycol‐Water Solutions: I . Electrochemical Kinetics

A variety of PEG‐400 water solutions that were 0.0034 m were studied with a Pt RRDE. From cathodic disk polarization curves, anodic ring currents, and collection experiments one concludes that Cu(I) is more stable in PEG‐400 than in water. Copper metal is oxidized to Cu(I) and Cu(II) reduced to Cu(I) as first steps. Pseudo exchange current densities were obtained at mixed potentials {where anodic current due to Cu → Cu(I) equals cathodic current due to Cu(II) → Cu(I)}. The following was found, ( i ) the overpotential needed to obtain a decade of current for copper oxidation and cupric reduction in PEG‐400 is three times larger than in water, ( ii ) the pseudo exchange densities are over an order of magnitude lower in PEG‐400; ( iii ) the mixed potentials become more positive with increasing PEG‐400 concentrations.