Capacitance Measurements for Evaluating Electrochemical Double‐Layer Models and Potentials of Zero Charge: A Reassessment

ChemPhysChem, vol. 26, pp. e202401088

Abstract

Differential capacitances (DCAPs) derived from electrostatic Gouy-Chapman-type models for electrochemical double layers (DLs) typically show valley-, bell-, or camel-type profiles as a function of the potential, centered around the potential of zero charge. These DCAP profiles are routinely evaluated with measured potential dependencies of capacitances. Here, the influences of hydrogen evolution, oxygen reduction, and oxide formation on the potential dependence of the capacitance of a polished gold electrode are experimentally examined. These parasitic reactions are found to cause most of the potential-dependent capacitance features that are typically attributed to intrinsic DL properties. With these insights, the historical development of the literature regarding the development of the theoretical framework in relation to capacitance measurements is critically reevaluated. As a result, drawbacks of the 100-year-old Gouy-Chapman theory for the DL are identified. Moreover, DCAPs as differences of electrostatic states are discussed as unable to portray measured capacitances that result from capacitive-resistive and dynamic charge displacements in the DL. Hence, the links between theories and experiments are critically assessed, motivating the need for more advanced atomistic models to adequately portray the DL.

Authors 3

1. Maximilian Schalenbach corresponding

   Forschungszentrum Jülich

   Affiliation as printed

   Institute of Energy Technologies (IET‐1): Fundamental Electrochemistry Forschungszentrum Jülich 52425 Jülich Germany

   Forschungszentrum Jülich GmbH IEK-9 Wilhelm-Johnen-Straße 52425 Jülich GERMANY

2. Hermann Tempel

   Forschungszentrum Jülich

   Affiliation as printed

   Institute of Energy Technologies (IET‐1): Fundamental Electrochemistry Forschungszentrum Jülich 52425 Jülich Germany

   Forschungszentrum Julich ICG: Forschungszentrum Julich GmbH Institute of Energy Technologies (IET-1): Fundamental Electrochemistry Wilhelm-Johnen-Str. 1 52425 Jülich GERMANY

3. Rüdiger‐A. Eichel Aachen Institute of Physical Chemistry

   RWTH Aachen University · Forschungszentrum Jülich

   Affiliation as printed

   Institute of Energy Technologies (IET‐1): Fundamental Electrochemistry Forschungszentrum Jülich 52425 Jülich Germany

   Institute of Physical Chemistry RWTH Aachen University 52062 Aachen Germany

   Forschungszentrum Julich ICG: Forschungszentrum Julich GmbH Institute of Energy Technologies (IET-1): Fundamental Electrochemistry Wilhelm-Johnen-Str. 1 52425 Jülich GERMANY