Electrodeposition and Dealloying of Nickel- Cobalt and Nickel- Cobalt-Copper Thin Films
Dr. Jennifer Hampton
This project focuses on characterizing nickel-cobalt and nickel-cobalt-copper electrodeposited thin films. These films can be engineered to have high surface areas, giving them fuel cell and capacitance-related applications. Using a threeelectrode electrochemical cell, metal alloys are deposited from solution onto a gold substrate. These films are then studied in a scanning electron microscope (SEM) with an energy dispersive x-ray spectroscopy (EDS) attachment to determine their structures and compositions. It was found that when nickel and cobalt are deposited together, there is consistently a higher ratio of cobalt in the film than in the solution. When nickel, cobalt, and copper are deposited together, the ratios in the film are generally closer to those in the solution, but there is more nickel in the film than in the solution. The nickel-cobalt and nickel-cobaltcopper films are then electrochemically dealloyed. To dealloy the films, a steadily increasing potential is placed between the working and counter electrodes, reoxidizing the metals and pulling them off of the substrate. Different metals reoxidize at different potentials, so depending on when one stops the potential, it is possible to pull out certain metals, leaving others behind. When dealloying the nickel-cobalt films, nickel and cobalt strip out of the film in nearly equal amounts, despite cobalt reacting at a lower potential. When dealloying nickelcobalt- copper, nickel and cobalt are kinetically stabilized, and the copper pulls out, leaving a porous nickel-cobalt film behind. Preliminary results also suggest that dealloying the nickel-cobalt-copper films increases their capacitances.
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