PNNL

Abstract

Hydronium segregates to the surface of H2O (D2O) ice films grown on Pt(111) above 151K (158K). This is observed as from the voltage that develops across the films, utilizing work function measurements. The dependence of this voltage on the film’s thickness is explained by a simple equilibrium model: as the film grows, most of the surface ions migrate so as to remain at the ice-vacuum interface, while a fixed percentage (~0.05%) take the thermodynamically-unfavored route, to become incorporated into the growing bulk ice. This model implies a delta-G of about +0.1eV for the movement of ions from the ice surface into the bulk ice.