Entropy Effects on Reactive Processes at Metal-Solvent Interfaces

The Journal of Physical Chemistry C, vol. 128, pp. 7892–7902

Abstract

High Resolution Image Download MS PowerPoint Slide Obtaining a reliable estimate of the reaction entropy is of utmost importance for the proper prediction of the reaction-free energies of chemical transformations at electrochemical interfaces. In this realm, we demonstrate the suitability of the two-phase thermodynamic (2PT) model and classical molecular dynamics simulations for the accurate and computationally efficient determination of the entropies of reactive species in a solvent environment. We present a systematic analysis of the entropies of different alcohol species in bulk solution and at platinum (Pt), silver (Ag), and lead (Pb) surfaces. The key observation is a metal-specific entropy reduction at metal-water interfaces in comparison to the corresponding entropy values obtained for bulk aqueous solvents. Entropies are seen to decrease by at least 15% relative to the bulk environment. This effect is attributed to the reduction in rotational and translational entropy contributions. By comparison of these results with predictions of theoretical models, the origin of the cavitation entropy is revealed. Overall, we demonstrate that solvation effects exert a significant impact on the free energies of adsorption/desorption and CO 2 reaction-free energies that can cause changes of several orders of magnitude in reaction rates. Entropic effects are therefore highly relevant for the deciphering of electrochemical processes.

Authors 4

1. Oskar Cheong Aachen Chair of Theory and Computation of Energy Materials Faculty of Georesources and Materials Enginering

   Forschungszentrum Jülich · Jülich Aachen Research Alliance · RWTH Aachen University

   Affiliation as printed

   Chair of Theory and Computation of Energy Materials, Faculty of Georesources and Materials Enginering, RWTH Aachen University, Intzestrasse 5, Aachen 52072, Germany

   Institute of Energy and Climate Research (IEK-13), Forschungszentrum Jülich, Wilhelm-Johnen-Straße, Jülich 52425, Germany

   JARA Energy & Center for Simulation and Data Science (CSD), Jülich 52425, Germany

2. Fabian P. Tipp Aachen Chair of Theory and Computation of Energy Materials Faculty of Georesources and Materials Enginering

   Forschungszentrum Jülich · Jülich Aachen Research Alliance · RWTH Aachen University

   Affiliation as printed

   Chair of Theory and Computation of Energy Materials, Faculty of Georesources and Materials Enginering, RWTH Aachen University, Intzestrasse 5, Aachen 52072, Germany

   Institute of Energy and Climate Research (IEK-13), Forschungszentrum Jülich, Wilhelm-Johnen-Straße, Jülich 52425, Germany

   JARA Energy & Center for Simulation and Data Science (CSD), Jülich 52425, Germany

3. Michael Hermann Eikerling Aachen Chair of Theory and Computation of Energy Materials Faculty of Georesources and Materials Enginering

   Forschungszentrum Jülich · Jülich Aachen Research Alliance · RWTH Aachen University

   Affiliation as printed

   Chair of Theory and Computation of Energy Materials, Faculty of Georesources and Materials Enginering, RWTH Aachen University, Intzestrasse 5, Aachen 52072, Germany

   Institute of Energy and Climate Research (IEK-13), Forschungszentrum Jülich, Wilhelm-Johnen-Straße, Jülich 52425, Germany

   JARA Energy & Center for Simulation and Data Science (CSD), Jülich 52425, Germany

4. Piotr M. Kowalski corresponding

   Forschungszentrum Jülich · Jülich Aachen Research Alliance

   Affiliation as printed

   Institute of Energy and Climate Research (IEK-13), Forschungszentrum Jülich, Wilhelm-Johnen-Straße, Jülich 52425, Germany

   JARA Energy & Center for Simulation and Data Science (CSD), Jülich 52425, Germany