Surface topography and impedance of metal-electrolyte interfaces

The small-signal impedance of chemical cells with ‘‘blocking’’ electrodes is dominated at low frequencies (f<∼100 Hz) by the impedance of the metal-electrolyte interfaces which is accurately represented by ${\mathrm{Z}}_{\mathrm{i}}$=A(jω${)}^{\mathrm{-}\mathrm{n}}$. The frequency exponent n, n<1, is sensitive to the texture of the interface, and several recent theories have been proposed that relate n with the fractal dimension d¯ of the rough interface. We find no correlation between n and d¯ from experiments using aqueous electrolytes and metal and semiconductor electrodes.