Berlin 2018 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 19: Solid-liquid interfaces: Reactions and electrochemisty II (joint session O/CPP)
CPP 19.4: Talk
Monday, March 12, 2018, 17:30–17:45, MA 144
Microcalorimetric measurement of double layer charging in ionic liquids — •Jeannette Lindner1, Fabian Weick1, Stefan Frittmann1, Frank Endres2, and Rolf Schuster1 — 1Institute of Physical Chemistry, Karlsruhe Institute of Technology, Karlsruhe, Germany — 2Institute of Electrochemistry, TU Clausthal, Clausthal, Germany
The reversible molar heats, i.e., the Peltier heats of processes in the electrified double layer at an IL/Au(111) interface were measured via electrochemical microcalorimetry. The Peltier heat corresponds to the entropy change during electrochemical double layer charging. 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide was used as ionic liquid. We found a decrease of ΔRS by 143 J/(K*mol) between E vs. Pt = -0,9 V and +1,0 V and ΔRS = 0 for E vs. Pt = -0,25 V. ΔRS = 0 corresponds to the maximum of the double layer formation entropy SMax. We interpret SMax as the maximum of mixing entropy of cations and anions within a lattice gas model with negligible ionic interactions. As a consequence, SMax corresponds to the pzc (point of zero charge) of the system. In order to quantitatively explain the found magnitude of the S variations, one has to include entropy contributions from multiple layers.