On the mechanism of hydrophilicity of graphene

TL;DR

This paper reveals that the intrinsic hydrophilicity of graphene is linked to its Fermi level position, which can be modulated by substrates or doping, affecting water interaction and vapor condensation.

Contribution

It demonstrates that shifting graphene's Fermi level enhances its hydrophilicity, clarifying the intrinsic versus substrate effects through experiments and simulations.

Findings

Fermi level position influences graphene's hydrophilicity

Chemical and electrical doping modulate water interaction

Enhanced vapor condensation observed with Fermi level shifts

Abstract

It is generally accepted that the hydrophilic property of graphene can be affected by the underlying substrate. However, the role of intrinsic vs. substrate contributions and the related mechanisms are vividly debated. Here we show that the intrinsic hydrophilicity of graphene can be intimately connected to the position of its Fermi level, which affects the interaction between graphene and water molecules. The underlying substrate, or dopants, can tune hydrophilicity by modulating the Fermi level of graphene. By shifting the Fermi level of graphene away from its Dirac point, via either chemical or electrical voltage doping, we show enhanced hydrophilicity with experiments and first principle simulations. Increased vapor condensation on graphene, induced by a simple shifting of its Fermi level, exemplifies applications in the area of interfacial transport phenomena.