| Popis: |
Two electroneutrality and constant-field solutions of the diffusion–migration problem in steady-state conditions on microelectrodes, where both approximations admit analytical solutions, are compared. Analytical equations for the potential drop across the diffusion layer φ0 in terms of RT/F and the migration factor Y are obtained for three- and four-component systems containing two and three types of electroactive ions, respectively, and one type of ions that takes no part in the reaction. Both methods yield virtually identical φ0. The migration coefficients at large absolute values of φ0 noticeably differ. The Y vs. φ0 dependences in the two approaches different. The Y values yielded by these methods are close only at |φ0| ≪ 1. For real electrochemical reactions considered, the electroneutrality condition at the limiting current is fulfilled at electrode radii >1 μm and electrolyte concentrations >0.1 mM. |
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