Nitric-oxide adsorption and oxidation on Pt(111) in electrolyte solution under potential control

We studied the adsorption and oxidation of NO adlayers on Pt(1 1 1) prepared frorn different NO precursors in an electrochemical cell in situ by surface X-ray diffraction and ex Situ by X-ray photoemission spectroscopy. We found that NO adsorbs molecularly, independent of the preparation method. There is no relaxation of the outermost Pt atomic layer induced by the presence of adsorbed NO. We observe a Surface structure of the Pt(1 1 1) very similar to the clean surface prepared under ultra-high vacuum conditions. A surface mediated oxidation process of the NO towards NO2 is initiated at a potential of around 0.95 V vs. normal hydrogen electrode. The in Situ measurements of crystal truncation rods show that this process is accompanied by a significantly roughening of the surface. (C) 2002 Elsevier Science B.V. All rights reserved.