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Abstract:
The structural and electronic properties of unsupported Pd2Ga were investigated after different pre-treatments. Pd2Ga provides with respect to elemental Pd a significantly modified electronic structure with its d-band center being shifted away from the Fermi level. It was found that the electronic structure of the surface depends strongly on its pre-treatment and on the chemical environment. We report a detailed bulk and surface characterization of the intermetallic compound by means of XRD, DTA/TG/MS, SEM, XPS, and HR-TEM. At moderate temperatures, the bulk of Pd2Ga is chemically resistant against H-2 or O-2 atmosphere and against mechanical load. Contrariwise its surface is highly sensitive against even traces of oxidizing agents, leading quickly to a disparity between bulk and surface structure and composition. The reversibility of this dynamic effect depends on the degree of decomposition and on the sample history. An almost pure intermetallic surface can only be achieved in highly reducing atmospheres. (C) 2013 Elsevier Inc. All rights reserved.
