FORMATION OF AN H-BONDED WATER STRUCTURE AT Pt SURFACES INDUCED BY ADSORBED CARBON MONOXIDE

摘要

At Pt(111) and polycrystalline Pt, coadsorption of CO and H_2O at potentials above 0.35V causes the formation of an H-bonded water structure characterized by a blue shift of ca 40 cm~(-1) of the bending frequency and a band for the OH stretching observed at 3250 cm~(-1). This band was assigned in the UHV literature to crystalline ice. At the electrochemical interface, it could indicate that the H-bonded water structure extends three dimensionally towards the solution. The formation of this structure is induced by CO adsorption at potentials positive to zero charge, where water binds to Pt through the oxygen atoms. The three dimensional water clusters represent a barrier for CO oxidation.