Surface characterization of ordered intermetallic PtBi(0Â 0Â 1) surfaces by ultra-high vacuum-electrochemistry (UHV-EC)

Surface preparation and characterization of an ordered intermetallic PtBi(0 0 1) single crystal was performed by a combination of surface-sensitive electron spectroscopic techniques under ultra-high vacuum (UHV) conditions and conventional electrochemistry (EC). The atomic concentration of the clean surface was estimated (quantitative Auger analysis) as 54 at% Pt and 46 at% Bi; the LEED pattern exhibited a (1 × 1) structure. These results are in good agreement with expectations for a Pt-terminated PtBi(0 0 1) crystal surface. The electrochemical studies of the clean, well-ordered and smooth PtBi(0 0 1) single crystal were carried out in an H2SO4 supporting electrolyte and indicated that the electrode surface is Pt-terminated with a behavior similar to that of a pure Pt electrode. However, the intermetallic phase was found to be more prone to surface oxidation in the studied potential window (−0.30 V to +1.25 V vs. Ag/AgCl (sat'd NaCl)). Chemisorption of SO42-/HSO4- species was observed at potentials positive of the open circuit potential (OCP). Cycling in a supporting electrolyte gave rise to roughening of the electrode surface. This change is due to the presence of the chemisorbed species on the electrode surface.