Pt Skin Versus Pt Skeleton Structures of Pt3Sc as Electrocatalysts for Oxygen Reduction

• Published in: Topics in catalysis Vol. 57; no. 1-4; pp. 245 - 254
• Main Authors: Johansson, T. P., Ulrikkeholm, E. T., Hernandez-Fernandez, P., Malacrida, P., Hansen, H. A., Bandarenka, A. S., Nørskov, J. K., Rossmeisl, J., Stephens, I. E. L., Chorkendorff, I.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.02.2014
• Subjects: Catalysis; Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; Industrial Chemistry/Chemical Engineering; Original Paper; Pharmacy; Physical Chemistry; Angle resolved X-ray photoelectron spectroscopy; Temperature programmed desorption; Platinum; Oxygen reduction reaction; Scandium; Ion scattering spectroscopy; Carbon monoxide
• ISSN: 1022-5528; 1572-9028
• DOI: 10.1007/s11244-013-0179-y

In order for low temperature polymer electrolyte membrane fuel cells to become economically viable Pt catalyst loading must be significantly reduced. The cathode of the polymer electrolyte membrane fuel cell, where oxygen reduction takes place, is responsible for the main activity loss. The development of new materials for this reaction is essential in order to increase the overall effeciency of the fuel cell. Herein, we study the effect of ultra high vacuum annealing on the structure and activity of polycrystalline Pt 3 Sc. Upon annealing in ultra high vacuum a Pt overlayer is formed on the polycrystalline Pt 3 Sc. The reactivity of the overlayer is probed by temperature programmed desorption of CO. The onset of CO desorption is around 130 K lower on UHV annealed Pt 3 Sc than on Pt(111) and the temperature of the desorption peak maximum at saturation was ∼50 K lower on UHV annealed Pt 3 Sc, relative to Pt(111), consistent with the CO adsorption energies calculated using density functional theory calculations. Exposing the annealed Pt 3 Sc sample to 200 mbar O 2 at room temperature results in ∼14 % Sc oxide as measured by X-ray photoelectron spectroscopy. Electrochemical testing of the oxygen reduction reaction shows the same activity as sputter cleaned Pt 3 Sc.