Modeling and Experimental Study of the Electron Transfer Kinetics for Non-ideal Electrodes Using Variable-Frequency Square Wave Voltammetry

Aleksei N Marianov; Alena S Kochubei; Tanglaw Roman; Oliver J Conquest; Catherine Stampfl; Yijiao Jiang

doi:10.1021/acs.analchem.1c01286

Modeling and Experimental Study of the Electron Transfer Kinetics for Non-ideal Electrodes Using Variable-Frequency Square Wave Voltammetry

Anal Chem. 2021 Jul 27;93(29):10175-10186. doi: 10.1021/acs.analchem.1c01286. Epub 2021 Jul 15.

Authors

Aleksei N Marianov¹, Alena S Kochubei¹, Tanglaw Roman^{2

3}, Oliver J Conquest^{2

3}, Catherine Stampfl^{2

3}, Yijiao Jiang¹

Affiliations

¹ School of Engineering, Macquarie University, Sydney, New South Wales 2109, Australia.
² School of Physics, The University of Sydney, Camperdown, New South Wales 2006, Australia.
³ The University of Sydney Nano Institute, The University of Sydney, Camperdown, New South Wales 2006, Australia.

PMID: 34264072
DOI: 10.1021/acs.analchem.1c01286

Abstract

The knowledge of nonequilibrium electron transfer rates is paramount for the design of modern hybrid electrocatalysts. Herein, we propose a general simulation-based approach to interpret variable-frequency square wave voltammetry (VF-SWV) for heterogeneous materials featuring reversible redox behavior. The resistive and capacitive corrections, inclusion of the frequency domain, and statistical treatment of the surface redox kinetics are used to account for the non-ideal nature of electrodes. This approach has been validated in our study of Co^II/Co^I redox transformation for Co tetraphenylporphyrin (CoTPP) immobilized on carbon cloth and multiwalled carbon nanotubes (CNTs) - one of the most active heterogeneous molecular catalysts in carbon dioxide (CO₂) electroreduction. It is demonstrated that the modeling of experimental data furnishes the capacitance of the surface double layer C, uncompensated resistance R_u, symmetry coefficients α, kinetic constants k₀, and equilibrium redox potentials E⁰ in one experiment. Moreover, the proposed method yields a stochastic map of the redox kinetics rather than a single value, thus exposing the inhomogeneous nature of the electrochemically active layer. The computed parameters are in excellent agreement with the results of the classic methods such as cyclic voltammetry and fall in line with the reported CoTPP catalytic activity. Thus, VF-SWV is suitable for the study of high-level composites such as covalent organic frameworks and organometallic-CNT mixtures. The resulting insights into the electron transfer mechanisms are especially useful for the rational development of the catalyst-support interfaces and immobilization methods.