Electrochemical Deposition for Electrochemical Energy Applications

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Proton exchange membrane fuel cells (PEMFC) are potential alternatives to fossil fuels as energy sources for automotive and stationary applications due to their high energy efficiency, high power density, quick start-up, low operating temperature, continuous operation, modularity, fuel flexibility and low greenhouse gas emissions. Despite these advantages, PEMFCs still face problems of high costs and less than desired durability that have limited their widespread use. These costs are linked to their reliance on platinum (Pt)-based electrocatalysts and the high Pt loading levels required in the cathode catalyst layer to compensate for the slow kinetics of the oxygen reduction reaction (ORR). ** Researchers have made concerted efforts to reduce the Pt requirement by using electrocatalysts consisting of Pt alloyed with less expensive transition metals such as Co, Fe and Ni. This approach not only reduces material costs, but also has been shown to improve fuel cell performance due to the higher activity of these alloys for the ORR than that of pure Pt. Nevertheless, the Pt loading is still much higher than the target set by the U.S. Department of Energy (DOE) and questions exist regarding the stability of these Pt alloy catalysts. ** The proposed research is aimed at applying electrodeposition techniques to fabricate Pt-Co catalyst films with improved ORR activity and stability, while reducing Pt loading. Electrodeposition is not as widely used to fabricate Pt-based catalysts as other methods although it has some advantages and has shown success in the past. The objective of the proposed research is to more fully explore these advantages by applying novel modulated and pulsed techniques that provide more operating variables to control alloy composition and deposit morphology than is possible with DC plating. A novel and simple method that takes advantage of the observed behaviour of Pt-Co deposition will be developed to fabricate catalyst films with tunable composition profiles which will then be analyzed for their ORR activity and stability. If successful, this could increase Pt utilization enough to lower Pt loading to the DOE target level and still be able to improve the ORR activity. ****************************************