Electrochemical Reduction of Oxide Layers

Oxide layers formed on the electrode surface can be identified by (photo) electrochemical or spectrophotometric methods. In voltammetry, an electrochemical activity of CU2O can be also employed. The following process occurs at sufficiently high cathodic polarizations  

Voltammetric data were used when investigating temperature effects in the ligand-deficient Cu Cu(II), ethylenediamine system [23]. Analysis of the data obtained with different Ugands shows [22] that the formation of oxide layers becomes more intensive when the complexation degree of the solutions decays and, consequently, the Cu concentration increases. This gives grounds to consider the process (10.2) as the main rate determining step. Then, the rate of oxide formation should follow the equation  

005 M ethylenediamine, and 0.3 M K2SO4 (pH 5.3). Prior to experiments, copper electrodes were exposed to the same solution at temperatures indicated at the curves. 

As the peak current may serve as a measure for the CU2O formation rate, the term w in this relationship may be replaced by ip. 

In the case of a heterogeneous reaction, its rate maybe defined dLSW = A dT/dt, where A is a surface area and T is a surface concentration (adsorption) of the solid product (CujO) formed. With established T and AE values and simulated concentration of Cu ions, Eq. (10.10) yields = 0.17 s . The obtained result shows that CU2O formation is not very fast. It follows from the analysis of its kinetics that approximately two monolayers could be formed over 1 min, provided that CU2O is uniformly distributed on the electrode surface. However, as we shall see next, it does not always happen. 

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