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Nanoscale Structuring in Au–Ni Films Grown by Electrochemical Underpotential Co‐deposition
Author(s) -
Liang Defu,
Rajput Parasmani,
Zegenhagen Jorg,
Zangari Giovanni
Publication year - 2014
Publication title -
chemelectrochem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.182
H-Index - 59
ISSN - 2196-0216
DOI - 10.1002/celc.201300214
Subject(s) - materials science , overpotential , alloy , nanoscopic scale , grain boundary , nanostructure , underpotential deposition , grain size , deposition (geology) , phase (matter) , chemical engineering , nanotechnology , ternary operation , electrochemistry , chemical physics , metallurgy , microstructure , cyclic voltammetry , chemistry , electrode , paleontology , organic chemistry , sediment , engineering , biology , computer science , programming language
Nanoscale phase separation is a simple but powerful method for the self‐assembly of nanostructures, which enables properties to be tuned by tailoring the phase composition, size, and topology of the structures. We demonstrate, contrary to thermodynamic predictions, the spontaneous nanoscale phase separation of Au–Ni alloy films, grown by electrochemical underpotential deposition of Ni onto a surface constantly renewed by the ongoing reduction of Au at overpotential. Strain‐energy relaxation during film growth, in combination with the net attractive interaction between Au and Ni atoms, results in the dynamic formation of a nanoscale alloy structure, consisting of Au‐rich grains of about 5 nm in size surrounded by relatively thick (2–3 nm) Ni‐rich grain boundaries. The estimated cohesive energy of such alloy configurations is stronger than that of the phase‐separated mixture, suggesting the formation of an unexpected local equilibrium configuration for the Au–Ni binary system, stabilized by the grain nanosize and the high density of grain boundaries.