Ice Formation via Deposition Mode Nucleation on Bare and Alcohol-covered Graphite Surfaces

TL;DR

This study investigates how alcohol coatings on graphite surfaces influence water ice formation at low temperatures, revealing that methanol promotes smooth ice while butanol hinders water evaporation, with implications for atmospheric ice nucleation.

Contribution

It demonstrates how different alcohols alter ice morphology and water exchange on graphite surfaces, advancing understanding of heterogeneous ice nucleation mechanisms.

Findings

Methanol creates hydrophilic sites leading to smooth crystalline ice.

Butanol reduces water evaporation rate at 185 K.

Alcohols mainly reside at ice surfaces and interfaces.

Abstract

Deposition of water on aerosol particles contributes to ice cloud formation in the atmosphere with implications for the water cycle and climate on Earth. The heterogeneous ice nucleation process is influenced by physico-chemical properties of the substrate, but the mechanisms remain incompletely understood. Here, we report on ice formation on bare and alcohol-covered graphite at temperatures from 175 to 213 K, probed by elastic helium and light scattering. Water has a low wettability on bare and butanol-covered graphite resulting in the growth of rough ice surfaces. In contrast, pre-adsorbed methanol provides hydrophilic surface sites and results in the formation of smooth crystalline ice; an effect that is pronounced also for sub-monolayer methanol coverages. The alcohols primarily reside at the ice surface and at the ice-graphite interface with a minor fraction being incorporated into the growing ice structures. Methanol has no observable effect on gas/solid water vapor exchange whereas butanol acts as a transport barrier for water resulting in a reduction in ice evaporation rate at 185 K. Implications for the description of deposition mode freezing are discussed.