In Situ Electrochemical Impedance Spectroscopic Method for Determination of Surface Roughness and Morphological Convexity

Abstract

A novel in situ electrochemical impedance spectroscopy (EIS) method is developed for the determination of RMS roughness (h), electroactive roughness factor (R c *), and morphological convexity (H̅*) of the electrode surface. Our method uses the angular frequency of maximum phase (ω M ) in anomalous Warburg impedance to extract in situ RMS roughness (h). The compact electric double layer (C-EDL) formation frequency (ω H ) is used to extract the electroactive roughness factor and morphological convexity. The theory unravels the inverse square root dependence of h on ω M through an elegant equation, , where D is the diffusion coefficient of electroactive species. Similarly, the equation for the electroactive roughness factor is R c * = ω H 0/ω H and ω H 0 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.

A Unified Theory for H2 Evolution on Mo-Based Electrocatalysts

“…Nonetheless, the roughness and depth of the electrodes was not significant enough to warrant special treatment between catalysts (Table S2). Furthermore, based on these micrographs, the higher quantity of electrochemically available Mo 4+ in a -MoS x observed during voltammetric studies can be understood to arise from the bulk, since the differences in catalyst surface morphology between a -MoS x and the other catalysts (particularly MoP) was minimal.…”

Structural modulation of low-valent iron in LDH-derived Ni3Se4nanosheets: a breakthrough electrocatalyst for the overall water splitting reaction

“…Operando EIS is an effective tool to investigate the adsorption and desorption kinetics for OER processes at the electrode-electrolyte interface. [37][38][39][40] The corresponding Nyquist plots at different applied potentials are displayed in Fig. S11a and b, † which show the electrochemical behaviours of Fe@Ni 3 Se 4 and NiFe-LDH.…”

Theory for Diffusion: Migration Coupling-Induced Cathodic and Anodic Current Anomaly

“…The limitation of surface roughness in the solid electrode is circumvented by accounting for the dynamic contribution from roughness . This is achieved by multiplying eqs and with a dynamic roughness factor R *( t ), defined as R * ( t ) = ( 1 + R c * − 1 1 + 2 false( R normalc * − 1 ) D α t / h 2 ) where R c * is at the reaction surface or OHP and h is the RMS roughness . The working electrode with rod or wire geometry having a radius r 0 shows a long-time steady-state current response, and the above equation also accounts for the contribution from migration…”

“…where R c * is at the reaction surface or OHP and h is the RMS roughness. 37 The working electrode with rod or wire geometry having a radius r 0 shows a long-time steady-state current response, and the above equation also accounts for the contribution from migration. 28 i k j j j j j y { z z z z z i k j j j j j y…”