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Entropy Effects in Atom Distribution and Electrochemical Properties of Au x Pt 1− x /Pt(111) Surface Alloys
Author(s) -
Bergbreiter Andreas,
Alves Otávio B.,
Hoster Harry E.
Publication year - 2010
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201000105
Subject(s) - adsorption , scanning tunneling microscope , annealing (glass) , electrochemistry , configuration entropy , atom (system on chip) , materials science , chemistry , crystallography , chemical physics , nanotechnology , thermodynamics , physics , electrode , metallurgy , computer science , embedded system
We report on the structural and electrochemical properties of Au x Pt 1− x surface alloys prepared by Au vapour deposition onto Pt(111) followed by annealing to 1000 K. Driven by configurational entropy, Pt and Au atoms are distributed homogeneously over the surface. On the nm scale, however, atomically resolved scanning tunnelling microscopy images with chemical contrast reveal the formation of nm‐sized Pt‐rich and Au‐rich aggregates, similar to the behaviour recently reported for Pd x Ru 1− x /Ru(0001) [H. Hartmann, T. Diemant, A. Bergbreiter, J. Bansmann, H. E. Hoster, R. J. Behm, Surf. Sci. 2009 , 603 , 1439]. Based on the STM data, we determine the abundance of specific adsorption sites for different Au contents, and we derive effective pair interaction parameters that allow reproducing the lateral distribution in Monte Carlo simulations. Cyclic voltammograms of the surface alloys have many similarities with Pt(111). H ad and OH ad related features both decrease with increasing amount of Au. Both seem to adsorb only on Pt sites, but H ad requires smaller ensembles of Pt atoms than OH ad . The onset potential for H ad ‐formation decreases with increasing Au content. This is can be explained by an effect of the Au atoms on the entropy of adsorption.