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O: Fachverband Oberflächenphysik

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

O 106.3: Poster

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

Thermodynamic and kinetic data of the hydrogen evolution reaction (HER) from electrochemical microcalorimetry. — •Marco Schönig and Rolf Schuster — Karlsruher Institut für Technologie, Deutschland

The hydrogen evolution reaction (HER) is an often investigated model electrocatalytic reaction. However, there are still open questions, like the influence of the alkaline metal cations in alkaline solution[1].

We measured the exchanged heat during the HER on Pt upon short potential or current pulses. The evolved heat is made up of reversible and irreversible contributions, which can be disentangled by measuring with different pulse polarities[2]. From the reversibly exchanged heat we derived the reaction entropy. The irreversible contribution to the exchanged heat corresponds to the overpotential. Thus, from the calorimetric data we can derive the overpotential as a function of current density, which allows for the determination of the exchange current density of the reaction and provides an alternative to the determination of kinetic parameters from Tafel plots.

The determined reaction entropies agree well with the standard reaction entropy of the HER in the respective solutions [3]. For the exchange current density, we found 1.3 mA/cm2 for 0.1 M LiOH. For 0.1 M KOH and 0.1 M CsOH lower values were found, which is in accordance with trends observed in the literature[1].

[1] A.S. Bandarenka et al., ChemElectroChem 2018, 5, 2326.[2] R. Schuster, Curr. Opin. Electrochem. 2017, 1, 88.[3] B.E. Conway et al., J.Chem. Soc, Faraday Trans. 1 1978, 74,1373.