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O: Fachverband Oberflächenphysik

O 17: Solid-Liquid Interfaces I: Reactions and Electrochemistry

O 17.7: Hauptvortrag

Montag, 16. März 2020, 16:45–17:15, TRE Phy

Electrochemical microcalorimetry - measuring the entropy of electrochemical reactions — •Rolf Schuster — Karlsruhe Institute of Technology, Institute of Physical Chemistry, Karlsruhe, Germany

Electrochemical reactions are accompanied by heat transfer between the electrode/electrolyte interface and its surrounding. In electrochemical systems the reversible part of the exchanged heat is directly correlated with the entropy changes in the interface. This gives access to the reaction entropy of the electrochemical processes, including the charge transfer itself as well as non-Faradaic side processes like coadsorption or solvent reordering. The reaction entropy, as a thermodynamic quantity, provides complementary information, e.g., to the charge vs. potential relation, as usually probed by conventional electrochemical methods. We study heat effects during electrochemical surface reactions with minute conversions down to about 1% of a monolayer. This allows for monitoring of the reaction entropy as a function of the electrode potential, for example, during hydrogen adsorption on Pt or underpotential Cu-deposition on Au. After a general introduction, we will present examples for entropy changes upon adsorption processes and double layer charging on Au(111) and discuss the effect of configurational entropy of the adlayer. Time-resolved studies of the heat evolution during Cu-bulk deposition will demonstrate the implications from heat measurements on the reaction steps of this complex reaction.