Hydrophobic Water Probed Experimentally at the Gold Electrode/Aqueous Interface

Area of Science:

• Physical Chemistry
• Electrochemistry
• Surface Science

Background:

• Understanding aqueous phase electrochemistry requires knowledge of the electrode/water interface.
• Characterizing interfacial water structure under electrochemical conditions is experimentally challenging.

Purpose of the Study:

• To experimentally characterize the potential-dependent structure of interfacial water at a gold electrode.
• To provide molecular-level insights into hydrophobic interfaces in electrochemical systems.

Main Methods:

• Utilized interface-specific vibrational spectroscopy.
• Employed a thin film electrochemical cell for in-situ measurements.
• Focused on a subpopulation of interfacial water molecules with one OH group oriented towards the gold surface.

Main Results:

• Observed that free-OH groups, indicative of a hydrophobic interface, interact weakly with the gold surface across all potentials.
• Found that the orientational distribution of these water molecules narrows as the potential approaches the potential of zero charge.
• Noted the disappearance of these free-OH groups upon oxidation of the gold electrode.

Conclusions:

• The study provides a quantitative description of interfacial water structure evolution with applied potential.
• Demonstrates the utility of vibrational spectroscopy for probing molecular-level details at electrochemical interfaces.
• Offers fundamental insights into the behavior of water at hydrophobic electrode surfaces during electrochemical processes.