Dissociation of water buried under ice on Pt(111)

Water on Pt(111) is generally thought to be nondissociative. However, by adsorbing a thick ice film [> 150 monolayers (ML)], substantial (similar to 0.16 to 1 ML) dissociation of the buried water occurs for T > 151 K. New temperature-programmed desorption peaks signal the dissociation (after careful isothermal predesorption of the overlying ice films). The buried water likely dissociates via the elevated temperatures and/or solvation changes experienced under the ice. Dissociation charges the growing ice film (up to +9 V) due to trapping of similar to 0.007 ML H3O+ at the vacuum-ice interface.