Surface-enhanced 2D IR shows that adding a small fraction of DMSO speeds up hydrogen-bond rearrangement at a gold electrode from roughly 10 ps in pure water to about 2 ps at 20 mol% DMSO — while the same mixtures slow water dynamics in the bulk. Interface and bulk respond in opposite directions to the same additive.
Picosecond electric field fluctuations mediate local environments that govern electrocatalysis at the electrode–water interface. Consequently, cosolvents modulate hydrogen-bond networks and interfacial dynamics. Here, we use surface-enhanced two-dimensional infrared (SE 2D IR) spectroscopy to quantify the effect of the cosolvent dimethyl sulfoxide (DMSO) on water dynamics by measuring the picosecond frequency fluctuation timescales of nitrile-based vibrational probes at a functionalized gold surface to extract H-bond lifetimes. We find that DMSO considerably accelerates interfacial H-bond rearrangements. In contrast, DMSO slows dynamics in the bulk, consistent with long-lived water–DMSO microdomains. The interface versus bulk comparison shows that DMSO disrupts cooperative H-bonding of water by inducing disorder at the interface, speeding up H-bond rearrangement.
- surface-enhanced 2D IR
- electrode interface
- hydrogen-bond dynamics
- DMSO
- cosolvent
- nitrile probe
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