Hydroxyl Groups on the Graphene Surfaces Facilitate Ice Nucleation

Area of Science:

• Atmospheric Chemistry
• Climate Science
• Materials Science

Background:

• Carbonaceous materials (CM) are critical for cirrus cloud formation and Earth's climate.
• The precise role of CM in ice nucleation is unclear due to complex surface chemistry and morphology variations.
• Understanding ice nucleation on CM is vital for climate modeling.

Purpose of the Study:

• To independently investigate the influence of surface chemistry versus morphology of CM on ice nucleation.
• To clarify the specific chemical functionalities that promote or inhibit ice nucleation on graphene-based surfaces.

Main Methods:

• Studied ice nucleation on highly oriented pyrolytic graphite (HOPG) surfaces.
• Treated HOPG surfaces with various plasmas to control surface chemistry (hydroxyl and carboxylic groups) and morphology.
• Applied classical nucleation theory for analysis.

Main Results:

• Increased density of hydroxyl groups on graphene surfaces significantly enhanced ice nucleation activity.
• Introduction of carboxylic groups showed no observable effect on ice nucleation.
• Higher hydroxyl group density correlated with increased binding energy between ice nuclei and the graphene surface.

Conclusions:

• Surface hydroxyl groups on graphene are key drivers of ice nucleation activity.
• The binding energy between the ice nucleus and the surface, influenced by hydroxyl groups, facilitates critical ice nucleus formation.
• This research clarifies the role of specific surface chemistries in ice nucleation by CM.