Electrodeposition and Dealloying of Nickel-Cobalt Thin Films
Dr. Jennifer Hampton
A nanoporous thin film’s high surface area allows it to act as a particularly efficient capacitor and gives it enhanced catalytic properties. This project focuses on the electrodeposition and dealloying of nickel-cobalt thin films with the purpose of creating such a nanoporous structure on the surface of the film. Using an electrochemical cell and a three-electrode system nickel-cobalt films of various ratios were deposited onto gold substrates. A scanning electron microscope (SEM) with an energy dispersive x-ray spectroscopy (EDS) attachment was used to observe and characterize each sample’s appearances, structures, and compositions. The depositions were remarkably uniform and smooth. The only defining characteristic was a large number of tiny holes measuring fractions of a micron scattered across the surface in varying concentrations. Analysis of the data gathered from the EDS showed that the percentage of cobalt in the film averaged nearly double that in the solution, suggesting that, when the two are deposited together, cobalt deposits at a much higher rate than nickel. Select samples were then dealloyed in the same electrochemical cell. This was achieved by reversing the potential across the electrodes, and, since cobalt re-oxidizes at a lower potential, it should strip off first, leaving behind an especially nanoporous surface. Preliminary results from the EDS suggest that dealloying cobalt from a nickel-cobalt sample is more likely with a higher cobalt to nickel ratio on the film.
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