Polarization Curves With Included Ohmic Potential Drop

The polarization curves for the electrodeposition process, which include the Ohmic voltage drop, can be obtained as follows, assuming = 1 in all cases.7,9,24 This will be performed for a one-electron transfer process and /3 = 0.5, meaning y = O.5.7 

Using (43) with y = 0.5 and jo/j. = 100, 10, 1, and 0.01, /c = lO 120 and /a = 10- /120, and jy = 50 and 10mAcm-2, the dependences presented by the dashed line in Figs. 7-10 are obtained. The Ohmic potential drop is not included in the calculated polarization curves depicted in Figs. 7-10 by the dashed line. It follows from Figs. 7-10 that for large values of jo/jh, electrochemical polarization can probably be neglected but mass-transfer limitations are present in all cases, which can also be shown by differentiation of (7). 

On the other hand, the measured value of overpotential, is given by  

For a 1 M solution of a typical fully dissociated electrolyte, the value of k is around 0.1 S cm-1, L can be taken as 0.2 cm, and /), = 50 mAcm-2 and 10 mA cm-2. Using these given values, as well as k = 0.033 Scm-1, (51), and the diagrams presented in Figs. 7-10 by the dashed line, polarization curves including the Ohmic potential drop can be obtained, as shown in Figs. 7-10 by the solid line. 

In the case under consideration, complete Ohmic control of the deposition process can be expected for 70//L 100 up to a current density about 0.95yh (Fig. 7) and for yo/yh = 10 up to 0.6yh (Fig. 9). It is obvious from Figs. 7-10 that, regardless of the shape of the polarization curve, which depends on the jo/jh ratio and /c, a limiting diffusion current density plateau is present in all cases. 

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Polarization Curves with Included Ohmic Potential Drop... 

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