Two-dimensional Cobalt-Platinum Nanoframes: Synthesis, Structure, and Electrochemical Oxygen Reduction Activity
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Proton exchange membrane (PEM) fuel cells which convert hydrogen and oxygen to electricity have attracted significant attention due to their high efficiency and clean byproducts. Electrochemical Oxygen Reduction Reaction (ORR) catalysts with high activity and improved stability are needed. Catalyst stability at elevated potentials is a particularly important and unsolved problem. Most commonly used ORR catalysts are carbon-supported platinum (Pt)/Pt-alloys. However, carbon degradation occurs at high electrochemical potentials resulting in performance degradation of the catalyst. This project evaluated the synthesis, structure, and properties of Co-Pt two-dimensional nanoframes which act as carbon-free ORR catalysts. The Co-Pt 2D nanoframes catalysts were synthesised using a three-step process: (i) synthesis of cobalt hydroxide nanosheets with high surface area, (ii) deposition of Pt onto the cobalt hydroxide nanosheets, and (iii) heat treatment under reducing conditions to facilitate interation of Co and Pt. The ORR specific and mass activity of Co-Pt-200 were determined to be 8 and 3 times higher than Pt/C, respectively. The ORR activities are higher than any activities of Co-Pt reported to date. The effects of thermal treatment temperature and adding a third transition metal on the ORR catalytic activity were also evaluated.