In Situ Electrochemical Impedance Spectroscopic Method for Determination of Surface Roughness and Morphological Convexity
Rama Kant, Himanshi Goel
Abstract
A novel in situ electrochemical impedance spectroscopy (EIS) method is developed for the determination of RMS roughness (h), electroactive roughness factor (Rc*), and morphological convexity (H̅*) of the electrode surface. Our method uses the angular frequency of maximum phase (ωM) in anomalous Warburg impedance to extract in situ RMS roughness (h). The compact electric double layer (C-EDL) formation frequency (ωH) is used to extract the electroactive roughness factor and morphological convexity. The theory unravels the inverse square root dependence of h on ωM through an elegant equation, h=D/ωM, where D is the diffusion coefficient of electroactive species. Similarly, the equation for the electroactive roughness factor is Rc* = ωH0/ωH and ωH0 is the smooth electrode C-EDL formation frequency. These equations are validated for the nanoparticles deposited and mechanically roughened Pt electrodes. Finally, this in situ method is applicable for both low and high roughness electrodes which transcend the limitations of contemporary methods.