Regensburg 2022 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 38: Solid-Liquid Interfaces 4: Reactions and Electrochemistry

O 38.1: Topical Talk

Mittwoch, 7. September 2022, 10:30–11:00, H4

Electrochemical Microcalorimetry — •Rolf Schuster and Marco Schönig — Institute of Physical Chemistry, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany

We investigate electrochemical reactions at single electrodes by measuring the accompanying heat changes. The heat reversibly exchanged during an electrode process is directly correlated to the reaction entropy of the half-cell reaction including all side reactions, e.g., ordering processes of the solvent or coadsorption processes of anions. Thus, measuring the heat exchange during an electrochemical process provides independent information on the ongoing reaction, which is complementary, e.g., to the potential-current relation, usually measured by cyclic voltammetry or impedance spectroscopy.

In this contribution we will briefly discuss some theoretical aspects of electrochemical microcalorimetry of single electrodes and present our strategy to measure the heat evolution upon surface electrochemical processes. With our setup we are sensitive to heat effects originating from minute conversions of a few percent of a monolayer of an electroactive species.

We will present examples for entropy changes upon anion adsorption and double layer charging on Au(111) and discuss the effect of configurational entropy of the adlayer. The hydrogen adsorption on Pt-films deals as an example of a prototypical surface electrochemical reaction. Time-resolved studies of the heat evolution during Cu bulk deposition will demonstrate the implications from heat measurements on the subsequent reaction steps of this complex reaction.