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Sulphide formation on the surface of binary AgPd alloys studied by XPS, AES, SEM/EDX
Author(s) -
Hautaniemi J.,
Hein M.,
Juhanoja J.,
Suoninen E.
Publication year - 1988
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/sia.740120706
Subject(s) - palladium , x ray photoelectron spectroscopy , layer (electronics) , crystallite , grain boundary , metal , substrate (aquarium) , surface layer , materials science , metallurgy , dissolution , diffusion , analytical chemistry (journal) , chemistry , chemical engineering , microstructure , nanotechnology , catalysis , biochemistry , oceanography , chromatography , geology , engineering , physics , thermodynamics
Formation of a sulphide layer on the surface of AgPd alloys has been studied by XPS, AES, SEM/EDX and optical microscopy. In accordance with earlier studies of sulphidization of AuAgCuPd alloys, no palladium‐enrichment can be observed in the sulphide layer formed on AgPd samples treated in Na 2 S solutions. Strong Pd‐enrichment is observed underneath the sulphide layer on the surface of the metal substrate. The enrichment takes place rather quickly and is associated with a palladium‐deficient layer underneath the substrate surface, suggesting diffusion of palladium to the surface of the metal phase. In polycrystalline materials sulphidization also takes place along the grain boundaries. The sulphide phases on the grain boundaries seem to act as channels for the migration of the silver atoms to the sample surfaces. This process leads to further sulphidization of the whole sample surface and overlaps the direct sulphidization which eventually stops because of the formation of a palladium‐enriched layer. The grain boundary connected process is strongly influenced by the composition of the electrolyte in which the sample is immersed.