Tuning Hydrogen Bond Networks at Gold Electrodes: A Study of Potential-Dependent DMSO-Water Interfaces

Understanding the behavior of hydrogen bond (H-bond) networks at electrode interfaces is the first step towards optimizing electrochemical processes. This study investigates the potential-dependent interfacial environment of dimethyl sulfoxide (DMSO)‒water mixtures at gold electrodes using a combination of surface-enhanced infrared absorption spectroscopy (SEIRAS) and constant potential molecular dynamics (MD) simulations. SEIRAS provides in situ spectroscopic data on H¬¬ bonding populations and cosolvent enrichment at the interface, while MD simulations offer an atomistic view of H bond configurations and molecular orientations under applied potentials. Our results demonstrate that applied electrostatic potential influences the interfacial H¬¬ bonding environment. Negative potentials produce enrichment of DMSO and a reorientation of interfacial water molecules, which leads to a slight increase in H-bonded populations, particularly at lower DMSO concentrations. Conversely, positive potentials show a reduced impact on the H bond structure. The effects are different at higher DMSO concentrations where DMSO‒DMSO interactions dominate. Despite DMSO being electrically neutral, both experimental and simulation data reveal a measurable modulation of interfacial enrichment and H¬¬ bond populations as a function of potential.