Journal
JOURNAL OF ALLOYS AND COMPOUNDS
Volume 667, Issue -, Pages 302-309Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/j.jallcom.2016.01.181
Keywords
Metallic glasses; Nanostructured materials; Catalysis; Dealloying
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Funding
- European Commission, Marie Curie Actions - Initial Training Networks (ITN) in the frame of the project VitriMetTech - Vitrified Metals Technologies and Applications in Devices and Chemistry [607080 FP7-PEOPLE-2013-ITN]
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In this work, electrochemical de-alloying of an amorphous alloy, Au40Cu28Ag7Pd5Si20, cast in ribbon form by melt spinning, has been performed, obtaining self standing nanoporous materials suitable for use as electrodes for electrocatalytic applications. The de-alloying encompasses removal of less noble elements and the crystallization of Au, resulting in interconnected ligaments whose size and morphology are described as a function of time. Depending on de-alloying time, the crystals may contain residual amounts of Cu, Ag and Pd, as shown by Auger Electron Spectroscopy (AES), Energy Dispersive Spectroscopy (EDS) and Cyclic Voltammetry (CV) in a basic solution. Current density peaks in the 0.16-0.28 V range (vs Ag/AgCl) indicate that the porous ribbons are active for the electro-oxidation of methanol. The partially de-alloyed samples, which still partially contain the amorphous phase because of the shorter etching times, have finer ligaments and display peaks at lower potential. However, the current density decreases rapidly during repeated potential scans. This is attributed to the obstruction of Au sites, mainly by the Cu oxides formed during the scans. The fully de alloyed ribbons display current peaks at about 0.20 V and remain active for hundreds of scans at more than 60% of the initial current density. They can be fully re-activated to achieve the same performance levels after a brief immersion in nitric acid. The good activity is due to trapped Ag and Pd atoms in combination with ligament morphology. (C) 2016 Elsevier B.V. All rights reserved.
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