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 Zᵢ=A(j{ω})^-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.