SurfaceScience21 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 106: Poster Session VIII: Poster to Mini-Symposium: Electrified solid-liquid interfaces III

O 106.2: Poster

Donnerstag, 4. März 2021, 13:30–15:30, P

Entropy changes during adsorption of pyridine on Au(111) in aqueous solutions — •Katarina Josifovska, Marco Schönig, and Rolf Schuster — Karlsruhe Institute of Technology, Kaiserstraße 12, 76131 Karlsruhe

The adsorption of pyridine on gold surfaces has been often studied by applying various electrochemical, microscopic and spectroscopic techniques. Corresponding to reported data, pyridine adsorption occurs in anodic direction in two different structural orientations [1,2,3].

In attempt to describe the adsorption, we used different concentrations of pyridine in aqueous solutions over Au(111), on which we conducted electrochemical microcalorimetric measurements in our home-build calorimeter [4]. We measured the Peltier heat which provides direct information on the reaction entropy of the electrochemical processes, scanning the whole adsorption region.

Negative entropy was found for the anodic processes, with a strong minimum of ca. -170 J/mol*K that was observed at about the same potential at which the reorientation occurs. This entropy reduction is in line with adsorption of weakly solvated neutral molecules from the solution, but also other processes, such as ion transport, entropy from double layer polarization, and/or accompanying solvent reorientation might contribute.

[1] L. Stolberg et al., J. Electroanalytical Chem. 1991, 241, 307. [2] J. Li et al., J. Am. Chem. Soc. 2015, 137, 2400. [3] S. Iqbal et al., Electrochimica Acta 2015, 186, 427. [4] R. Schuster, Curr. Opin. Electrochem. 2017, 1, 88.