Impact of Electric Field on the Structural Dynamics of Water and Adsorbed Molecules near an Electrode Surface: Simulations of 2D IR Experiments

Heterogeneous catalysis involves the chemical transformation of molecules at an electrode surface, but experimentally probing the impact of the electric field on the structural dynamics of the molecules and any accompanying solvent dynamics remains a significant challenge. In this study, we conducted molecular dynamics simulations of a system comprising pure water in contact with gold (Au) electrodes coated with 4-mercaptobenzonitrile (4-MBN) molecules, as recently measured using 2D IR spectroscopy (Ryan, M. J. Proc. Nat. Acad. Sci. U.S.A. 2023, 120, e2314998120, 10.1073/pnas.2314998120). Our simulations revealed that the 4-MBN molecules can adopt two distinct conformations with different tilt angles and that the kinetics of switching between the two conformations depends on both the applied voltage and the packing of the monolayer. There is an accompanying change in solvation upon conformational switching. The results illustrate that the application of a voltage to an electrode alters both the solvation and molecular dynamics at the interface, which has implications for heterogeneous electrochemistry.