Dynamic Stabilization of Metal Oxide-Water Interfaces

Area of Science:

• Surface Science
• Computational Chemistry
• Materials Science

Background:

• Water-metal oxide interactions are vital for catalysis and geochemistry.
• Interfacial structures are often assumed to be static, even at room temperature.

Purpose of the Study:

• To investigate the dynamic nature of water adsorption on metal oxide surfaces.
• To compare experimental observations with theoretical simulations for a model system.

Main Methods:

• In situ synchrotron X-ray scattering.
• Density functional theory-based molecular dynamics simulations.
• Bond valence analysis for pK_a prediction.

Main Results:

• The (1102) termination of hematite (α-Fe2O3) is dynamically stabilized by picosecond water exchange.
• Simulations revealed frequent exchange between aquo groups and adsorbed water, consistent with experimental data.
• Even under dry conditions, an ultrathin water film exhibits dynamic exchange.

Conclusions:

• The dynamic water exchange significantly influences the time-averaged interfacial structure.
• This dynamic process impacts proton-transfer reactions and acid/base reactivity at the interface.
• Findings offer new insights into metal oxide-water interfacial chemistry.