Self-affine roughness influence on redox reaction charge admittance

In this work we investigate the influence of self-affine electrode roughness on the admittance of redox reactions during facile charge transfer kinetics. The self-affine roughness is characterized by the rms roughness amplitude w, the correlation length ξ, and the roughness exponent H (0 < H < 1). Our calculations allow analytic expressions to be derived for the admittance as a function of the characteristic self-affine roughness parameters. Furthermore, it is shown that the magnitude of the reaction admittance is strongly influenced by the local roughness exponent H or the fine roughness details at short roughness wavelengths, while the influence of the lateral correlation length ξ or the long wavelength roughness ratio w/ξ is of secondary importance. In addition, the dynamic roughness evolution can strongly influence the reaction admittance and it should taken carefully into consideration.