The wetting of H2O by CO2

Area of Science:

• Interfacial Science
• Computational Chemistry
• Geoscience

Background:

• Biphasic interfaces exhibit unique properties distinct from bulk phases.
• The carbon dioxide-water (CO2-H2O) interface is crucial for carbon cycle and carbon capture and sequestration (CCS) schemes.
• Open questions remain regarding interfacial tension and CO2 phase behavior at the CO2-H2O interface.

Purpose of the Study:

• To provide an ab initio-level description of the CO2-H2O interface.
• To address ambiguities in interfacial tension and CO2 phase behavior.
• To leverage machine-learned potentials and enhanced statistical sampling for accurate simulations.

Main Methods:

• Utilizing ab initio-quality simulations.
• Employing machine-learned potentials for accurate energy calculations.
• Implementing enhanced statistical sampling techniques.
• Predicting interfacial tensions across a range of pressures (1-500 bars).

Main Results:

• Predicted interfacial tensions align well with experimental data.
• Observed buildup of an adsorbed, saturated CO2 film at low pressure (20 bars).
• The CO2 film exhibits bulk-like properties and preferential perpendicular alignment.
• CO2 monolayer formation correlates with reduced water structuring at the interface.

Conclusions:

• Machine-learned potentials accurately predict macroscopic properties of biphasic interfaces.
• Mechanistic insights into CO2 aggregation at the water interface are provided.
• Findings are highly relevant for geoscience, climate research, and materials science.