Hydrophobic Versus Hydrophilic Nature of the Gold-Water Interface Determined by Fluctuating Local Water Orientation

The interactions between water molecules and gold surfaces are central to biocompatibility and electrocatalysis, yet their fundamental nature remains highly controversial. Recent findings indicating a molecular-level hydrophobicity have challenged the classical view of gold being hydrophilic. Using surface-specific spectroscopy and ab initio simulations, we demonstrate that gold is neither hydrophobic nor hydrophilic in the classical sense, but exhibits strong electronic interactions with water, resulting in an orientation-dependent electronic heterogeneity. These findings are important for the properties of metal-aqueous interfaces with broad applications.