This is a copy of the slides presented at the meeting but not formally written up for the volume.

In situ synchrotron x-ray techniques are ideal for providing insight into the oxidation behavior of metals and alloys. Here, we present results from an in situ study of the early-stage processes during oxidation of (001) single crystal Cu-Ni alloys, of interest, for example, as catalysts of a number of important chemical reactions. Grazing incidence x-ray diffraction observations in controlled, elevated temperature oxidizing conditions reveal that, with increasing oxygen partial pressure (pO2), epitaxial cube-on-cube-oriented NiO islands form first, followed by other epitaxial orientations of NiO. As the pO2 continues to be increased, epitaxially-oriented Cu2O islands will also eventually nucleate and grow. In some cases, evidence is seen for the formation of internal, as well as surface oxide islands. Total reflection x-ray fluorescence observations provide a complementary sensitive measure of the changes in the alloy surface composition in response to changes in the composition of the gas environment in contact with the sample. Evidence is seen for Ni surface segregation under intermediate pO2 conditions where NiO, but not Cu2O nucleates and grows. In addition to describing the oxidation behavior of Cu-Ni alloys as functions of alloy composition, temperature, and pO2, we also will discuss the possible effects of the presence of Cu2O islands or oxygen-induced surface structure(s) on the activity of Cu or Cu-Ni surfaces in catalyzing the methanol oxidation reaction.