SKM 2023 – scientific programme

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O: Fachverband Oberflächenphysik

O 60: Solid-Liquid Interfaces I: Structure and Spectroscopy

O 60.11: Talk

Wednesday, March 29, 2023, 17:30–17:45, TRE Phy

A femtosecond resolved view of vibrationally assisted electron transfer across the metal/aqueous interface — •Zhipeng Huang, Manuel Bridger, Oscar Andres Naranjo-Montoya, Alexander Tarasevitch, Uwe Bovensiepen, Yujin Tong, and R. Kramer Campen — Faculty of Physics, University of Duisburg-Essen

Understanding heterogeneous charge transfer is crucial if we are to build the best electrolyzers, fuel cells and photoelectrochemical water splitting devices that chemistry allows. Since the elementary processes involved have characteristic timescales ranging from femto- to milliseconds, direct simulation of all relevant processes is not generally possible.

Here we demonstrate experimentally, using a novel two photon photovoltage approach, that for a prototypical system, a ferrocene terminate alkane thiol self-assembled monolayer (SAM) on gold in contact with aqueous electrolyte, charge transfer from the Au to the ferrocene can be induced by vibrational excitation of the ferrocene aromatic CH. Intriguingly the energy of the aromatic CH vibration, 0.38 eV, is a large fraction of the effective solvent interaction strength inferred for the ferrocene/ferrocenium system in prior electrochemical studies: 0.85 eV. Our results thus imply that, solvent may effect reduction/oxidation rates in electrocatalysis by coupling to a few, perhaps widely different in energy, vibrations. If shown to be generally true such a picture would suggest the necessity of moving beyond a single effective solvent interaction in theoretical descriptions of heterogeneous electron transfer.