We report a facile, low-temperature reaction between condensed-phase NO 2 and H 2 O that leads ultimately to the formation of a large concentration (θ 0 ) 0.42 monolayers) of adsorbed oxygen adatoms on a Au(111) surface. This reaction represents a novel route to generate surface oxygen on Au that can be utilized in fundamental studies of oxidation catalysis over Au such as low-temperature CO oxidation and the operation of Au converter tubes used in redox chemiluminesence detectors for atmospheric NO x . Also, this reaction may be relevant to heterogeneous processes occurring on ice particles in stratospheric clouds. This reaction is not specifically catalyzed by the Au(111) surface or by the defects present on the Au surface, and so this reaction may have some general utility for facile oxidation of unreactive surfaces.

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The adsorption properties of binary alloy surfaces may significantly deviate from those of the pure component metals. The physical origin of this deviation arises in a rather complex way from the distribution of both kinds of metal species and their interaction in the surface. In contrast to most other adsorption work on binary alloy surfaces we demonstrate and discuss here a clear-cut distinction between a pure geometrical ensemble effect and an electronic ligand effect on the adsorption of gas molecules by using an ordered alloy surface, namely Cu3Pt(111). Furthermore, we show the extent to which the chemical heterogeneity of the surface playing a role depends also on the nature of the adsorbate.

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