Surface reactions, solvation and adsorption phenomena of electrolytic adlayers on metal surfaces.

摘要

Fundamental understandings of electrolytic adlayers are important to areas like: batteries, ultra-capacitors, fuel cells, corrosion and atmospheric chemistry. In this dissertation, interactions of electrolytic adlayers are systematically examined using ultra-high vacuum surface analytical techniques. In particular, interactions of water with constituents of electrolytic adlayers are closely followed.;On clean Ag(110), water desorbs at 165 K and adsorbs as crystalline ice at 145 K. During continuous adsorption, water initially adsorbs with its molecular plane parallel to the surface, and then gradually tilts towards the surface normal as more water adsorbs. A layer-by-layer adsorption model is proposed for crystalline ice growth on Ag(110). When water is separately coadsorbed with hydroxyl and carbonate, water is stabilized to temperatures as high as 220 and 300 K, respectively. Both anions exhibit great surface solvation. An extended bilayer model is proposed for OH interactions with water, and isotopic exchange experiments have illustrated that (1) the extent of proton mobility in the adlayers, and (2) the migration of hydroxide ion into the water-ice multilayer.;On Pt(111), mutual displacement of water and methanol occurs in electrolytic adlayers. Adsorbed methanol monolayer is destabilized when it is co-adsorbed with hydrogen. However, methanol monolayer can be restabilized when water is introduced to the adlayer system. With addition of excess water, destabilization induced by hydrogen can be completely removed and methanol behaves as if it interacts only with water.;Interactions of Ru-modified Pt(111) with electrolytic adlayer has been studied. Ru adlayers were deposited with a low power electron beam heated evaporation source, and Ru can be probed with molecular nitrogen. Optimum activity of Ru/Pt(111) surfaces occurs when they are thermally activated to 573 K. Water can be stabilized to temperatures as high as 250 K on these surfaces, and partial dissociation of water occurs. However, adsorption of hydrogen and oxygen decreases when Pt(111) surface is adsorbed with Ru. The results in this work provide interesting insights into interactions of water with various aspects of electrolytic adlayers, and hopefully provide directions for future applied research.