Rotating disk electrode steady-state mass transfer

For a rotating disk electrode, the treatment of steady-state, mass-transfer-controlled electrode reactions applies, where the mass-transfer coefficient is mo = 0.61Dq Here, Dq is the dif-... 

In the absence of the following reaction, we think of the concentration profile for R as decreasing linearly from a value Cr(x — 0) at the surface to the point where Cr = 0 at 5, the outer boundary of the Nemst diffusion layer. The coupled reaction adds a channel for disappearance of R, so the R profile in the presence of the reaction does not extend as far into the solution as 5. Thus, the added reaction steepens the profile and augments mass transfer away from the electrode surface. For steady-state behavior, such as at a rotating disk, we assume the rate at which R disappears from the surface to be the rate of diffusion in the absence of the reaction [(mRCR(x = 0) see (1.4.8)] plus an increment proportional to the rate of reaction [/jikCj (x = 0)]. Since the rate of formation of R, given by (1.4.6), equals its total rate of disappearance, we have... 

A regime of simultaneous dissolution has also been found for Cu—Ni alloys in acidic chloride solutions. Rotating ring-disk electrode studies revealed an apparent Tafel region of the alloy and component polarization curves with mixed mass transfer and kinetic rate control [44, 45]. For a CugoNiio alloy, the kinetic parameters again indicate a coupling of the copper and nickel partial currents under steady state conditions [44]. 

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