COLL 527 |
| After decades of study water adsorbed on Pt(111) , whether in sub-monolayer, or multiplayer amounts, crystalline or amorphous, has been firmly established as non-dissociative, with water dissociation being energetically multiple kT's uphill. We show here, via carefully staged thermal desorption, compelling evidence that when buried under multilayer ice, water readily dissociates on Pt(111) between 151 and 170 K, and in monolayer amounts. This is supported by work function measurements, showing selective transport of a small fraction of the hydroniums produced, via an apparent surface potential minimum, upwards as the films are grown . This dissociation, easily understood to have been missed earlier, may now permit some reassessing the dissociation energy on Pt(111). Dissociation is permitted because either: the blocking of the desorption channel permits crossing a high activation barrier, and/or the overlying ice favors the dissociated state due to solvation, strain, or interfacial energy. |
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Water at Interfaces
2:00 PM-5:10 PM, Wednesday, 13 September 2006 Sir Francis Drake -- Tudor Room, Oral
Division of Colloid & Surface Chemistry |