In situ CO oxidation on well characterized Pt3Sn(hkl) surfaces: A selective review

Bimetallic single crystals Pt3Sn(1 1 0) and Pt3Sn(1 1 1) have been characterized for in situ CO oxidation. Surface composition and structure were established in ultra high vacuum (UHV) by Auger electron spectroscopy, low energy ion scattering spectroscopy (LEISS) and low energy electron diffraction (LEED). LEED patterns of Pt3Sn(hkl) are consistent with the surface composition, determined by LEISS, of ∼25 or 50 at.% Sn. Following UHV characterization crystals were transferred into the electrochemical environment where surface electrochemistry of adsorbed CO was studied in situ by infrared spectroscopy. Changes in band morphology and vibrational properties: splitting of the band and increase in the frequency mode, were found on Pt3Sn(hkl) and correlated to Pt(hkl) surfaces. Continuous oxidative removal of adsorbed CO starts as low as E < 0.1 V, which is an important property for CO-tolerant catalysts. In addition to electronic effects, other factors, such as surface structure and intermolecular repulsion between adsorbed species are responsible for high catalytic activity of Pt3Sn(hkl) alloys.