Entropic Stabilization of Water at Graphitic Interfaces

Area of Science:

• Physical Chemistry
• Surface Science
• Computational Materials Science

Background:

• The thermodynamic stability of water at interfaces with graphitic materials is crucial for understanding natural and industrial processes.
• It is widely assumed that graphite's multilayered structure enhances water wetting compared to single-layer graphene due to stronger van der Waals interactions.

Purpose of the Study:

• To investigate the dominant factors governing the thermodynamic stability of interfacial water on graphite versus graphene.
• To elucidate the molecular mechanisms behind the differential wetting behavior of water on these two graphitic surfaces.

Main Methods:

• Extensive computer simulations were performed to model water-graphitic surface interactions.
• Analysis of molecular correlation functions was employed to quantify interfacial properties.

Main Results:

• Interfacial water thermodynamics on graphite is primarily driven by surface entropy, rather than van der Waals interactions.
• Destabilization of the hydrogen bond network on graphite leads to an increase in low-frequency vibrational modes (translational and librational).
• This entropic effect results in greater interfacial stability on graphite compared to graphene, with a spectroscopic signature near 100 and 300 cm^-1.

Conclusions:

• Surface entropy plays a dominant role in the thermodynamic stability of water at graphitic interfaces.
• The findings challenge the conventional understanding based solely on van der Waals forces.
• This entropy-driven mechanism offers new insights into phenomena such as the hydrophobic effect.