SURFACE-SCIENCE SIMULATION STUDY OF THE ELECTROCHEMICAL CHARGE-TRANSFER REACTION (H)AD+(H2O)AD-](H3O+)AD+E-METAL ON PT(111) AND CU(110)

Abstract

By coadsorbing hydrogen and water on Pt(111) and Cu(110), and isotopically substituting (H)ad by (D)ad, we have unambiguously identified the occurrence of the electrochemical reaction (H)ad + (H2O)ad --> (H3O+)ad +e(metal)- in UHV. On Pt(111), a substantial fraction of the hydrogen is oxidized to (H3O+)ad, whereas on Cu(110), this does not occur. On Pt(111), the proton in the initial (H3O+)ad complex is seen to exchange readily with excess water. Hydrated proton formation on Pt(111) was also observed at higher temperatures, where water only has a finite residence time on the suface.