Combinatorial Electrodeposition Of Cobalt-Copper Material Libraries

A full cobalt-copper material library was successfully prepared from a single experiment by galvanostatic electrodeposition using a modified Hull cell. X-ray fluorescence spectroscopy (XRF) measurements showed, that a composition gradient of 28-96 at.% copper could be achieved. The change of the surface morphology and topography along the material library was examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM), respectively. X-ray diffraction (XRD) revealed a Vegard-like behavior of the face-centered cubic (fcc) cobalt-copper solid solution, as the lattice constant a can be linearly correlated with the atomic copper ratio. The work function, determined from scanning Kelvin probe (SKP) measurements, was expected to decrease gradually with increasing copper content, but was found to be highest (4.86 eV) for a shiny area within the material library (48-62 at.% Cu), indicating higher nobility. This result was confirmed by localized corrosion potential (E-corr) determinations performed by scanning droplet cell microscopy (SDCM). The unexpected high nobility in work function and E-corr for this region go hand in hand with a minimum in surface roughness within the material library. (C) The Author(s) 2016. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives 4.0 License (CC BY-NC-ND, http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reuse, distribution, and reproduction in any medium, provided the original work is not changed in any way and is properly cited. For permission for commercial reuse, please email: oa@electrochem.org. All rights reserved.