Issue 19, 2024

How microstructures, oxide layers, and charge transfer reactions influence double layer capacitances. Part 1: impedance spectroscopy and cyclic voltammetry to estimate electrochemically active surface areas (ECSAs)

Abstract

Varying the electrode potential rearranges the charges in the double layer (DL) of an electrochemical interface by a resistive-capacitive current response. The capacitances of such charge relocations are frequently used in the research community to estimate electrochemical active surface areas (ECSAs), yet the reliability of this methodology is insufficiently examined. Here, the relation of capacitances and ECSAs is critically assessed with electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) data on polished (Au, Ti, Ru, Pt, Ni, glassy carbon, graphite plate) and porous (carbon fleeces) electrodes. By investigating this variety of electrodes, the frequency-dependencies observed in the measured capacitances are shown to arise from the inherent resistive-capacitive DL response, charge transfer reactions, and resistively damped capacitive currents in microstructures (such as pores, pinholes, or cracks). These frequency-dependencies are typically overlooked when capacitances are related to ECSAs. The capacitance at the specimen-characteristic relaxation frequency of the resistive-capacitive DL response is proposed as a standardized capacitance-metric to estimate ECSAs. In 1 M perchloric acid, the polished gold electrode and the high-surface area carbon fleeces show ratios of capacitance-metric over surface-area of around 3.7 μF cm−2. Resistively damped currents in microstructures and low-conducting oxide layers are shown to complicate trustworthy capacitance-based estimations of ECSAs. In the second part of this study, advanced equivalent circuits models to describe the measured EIS and CV responses are presented.

Graphical abstract: How microstructures, oxide layers, and charge transfer reactions influence double layer capacitances. Part 1: impedance spectroscopy and cyclic voltammetry to estimate electrochemically active surface areas (ECSAs)

Supplementary files

Article information

Article type
Paper
Submitted
29 Sep 2023
Accepted
04 Dec 2023
First published
04 Dec 2023
This article is Open Access
Creative Commons BY license

Phys. Chem. Chem. Phys., 2024,26, 14288-14304

How microstructures, oxide layers, and charge transfer reactions influence double layer capacitances. Part 1: impedance spectroscopy and cyclic voltammetry to estimate electrochemically active surface areas (ECSAs)

M. Schalenbach, V. Selmert, A. Kretzschmar, L. Raijmakers, Y. E. Durmus, H. Tempel and Rüdiger-A. Eichel, Phys. Chem. Chem. Phys., 2024, 26, 14288 DOI: 10.1039/D3CP04743A

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