Nanoporous metallic structures formed from dealloying have recently attracted considerable interest due to a wide range of potential applications in areas such as catalysis, actuators, biomedical sensors and fuel cell electrodes. The Cu-Pd system is interesting as a model system for corrosion as well as a potential catalyst material. We report a combined in-situ X-ray diffraction (XRD) and ex-situ atomic force microscopy (AFM) study of the initial structural evolution during the selective dissolution of Cu from Cu3Pd (111) and Cu3Pd (100). The experiments were performed under potential control in 0.1 M H2SO4 solution. Below the critical potential, no distinct diffraction signal is evidenced by in-situ XRD but AFM reveals the existence of islands on the surfaces. At the critical potential, on both single crystal surfaces the formation of an epitaxial Pd layer exhibiting substrate orientation is evidenced by XRD. Ex-situ AFM imaging clearly showed at comparable stages the formation of larger nanoscale islands. We further compare and contrast the behavior of the dealloyed Cu-Pd surfaces with that of Cu-Au alloys.

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Nano-porous metals formed by dealloying have potential application in a variety of fields such as catalysts, actuators, biomedical sensors and fuel cells. Several aspects of the formation of porous surface during dealloying have not completely been understood. The Cu-Pd system is interesting as a model system for corrosion as well as a potential catalyst material. The initial dealloying and selective dissolution of single-crystals Cu 3 Pd (111) and Cu 3 Pd (100) in 0.1 M H 2 SO 4 in the potential range of 400-800mV has been studied. With in-situ X-ray diffraction (Synchrotron Light), we observed the epitaxial Pd layer peak to appear by increasing the potential close to the critical potential. Exsitu atomic force microscopy (AFM) showed the formation of nanoscale islands of Pd (20-50 nm). Our aim in this project is to study the initial steps of dealloying of well-defined Cu-Pd surfaces on the atomic scale and to compare the results to the Cu-Au system.