Electrical fluctuations next to an electrode to probe the properties of interfacial electrolytes Swetha Nair , Giovanni Pireddu, Benjamin Rotenberg CNRS, Sorbonne Université, France The fluctuations of physical quantities are often considered as noise that should be minimized with respect to a signal. In electrochemical processes, the charge exchange between electrode and electrolyte promotes chemical changes at the interface, and such interfacial electron transfer reactions serve as the foundation for important technologies that combine electrical and chemical energy. In this context, we use molecular simulations to investigate the link between solvent polarization fluctuations around a solute near an electrode and electron transfer kinetics (Marcus theory) and how these fluctuations are reflected in the charge fluctuation of the electrode [1,2,3] . It has also been observed that the metallicity of the electrode, which reflects its electronic structure, affects the electron transfer kinetics [4] . This metallic character can be captured in a simplified description via the so-called Thomas-Fermi screening length within the electrode [5,6] . This quantity can further be introduced in molecular simulations in the constant-potential ensemble [7] , which allowed in particular to uncover its role on the interfacial thermodynamics via the charge distribution within the electrode[8]. In order to understand the charge distribution induced on the surface by a single ion as a function of its distance from the electrode[9], we use classical molecular simulations of an ion in vacuum or water next to a graphite electrode with a tunable metallicity. Based on the 2D and radial distributions of the induced charge, we discuss the effects of the ion-surface distance and of the screening both in the metal (Thomas-Fermi length) and the solvent (described in the continuum picture by its permittivity). By comparing the simulation results with analytical predictions, we analyze the effect of the atomic structure of the electrode. Finally, we also compare analytically and numerically the case of a single ion and that of a periodic lattice of ions, since molecular simulations are done under periodic boundary conditions. This work is part of the ERC project SENSES (grant No. 863473). Project website: https://benrotenberg.github.io/erc-senses/ References 1. Marcus, R. A, J. Chem. Phys. 1965, 43, 3477−3489. 2. L. Scalfi, D. T. Limmer, A. Coretti, S. Bonella, P. A.Madden, M. Salanne, and B. Rotenberg, Phys. Chem. Chem. Phys. 2020, 22, 10480. 3. G. Pireddu and B. Rotenberg, Phys. Rev. Lett. 2023, 130, 098001. 4. Y. Yu, K. Zhang, H. Parks, M. Babar, S. Carr, I. M. Craig, M. Van Winkle, A. Lyssenko, T. Taniguchi, K. Watanabe, V. Viswanathan, D. K. Bediak, Nat. Chem. 2022, 14, 267−273. 5. M. Vorotyntsev and A. A. Kornyshev, Zh. Eksp. Teor. Fiz., 1980, 78(3), 1008–1019. 6. V. Kaiser, J. Comtet, A. Niguès, A. Siria, B. Coasne and L. Bocquet, Faraday Discuss., 2017, 199, 129–158. 7. L. Scalfi, T. Dufils, K. G. Reeves, B. Rotenberg, and M. Salanne, J. Chem. Phys. 2020, 153, 174704.
8. L. Scalfi and B. Rotenberg, Proc. Natl. Acad. Sci. U.S.A, 2021, 118, e2108769118. 9. G. Pireddu, L. Scalfi, and B. Rotenberg, J. Chem. Phys. 2021, 155, 204705.
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