Outermost Surface Structures and Oxygen Reduction Reaction Activities of Co/Pt(111) Bimetallic Systems Fabricated Using Molecular Beam Epitaxy

We studied oxygen reduction reaction (ORR) activities for outermost surfaces of 0.3 nm thick Co deposited on Pt(111) (Co0.3 nm/Pt(111)) bimetallic systems fabricated using molecular beam epitaxy at various Co deposition temperatures. Results show that Co0.3 nm/Pt(111) fabricated at temperatures lower than 393 K displays extra low-energy electron diffraction (LEED) spots outside the integer ones, indicating incoherent epitaxial growth of Co. A new IR band that is attributed to linearly bonded carbon monoxide (CO) on the Pt site influenced by neighboring Co atoms emerges at 2052 cm–1 for 333 K fabricated Co0.3 nm/Pt(111), in addition to the CO–Pt and CO–Co bands. With increasing fabrication temperature, the new band shifts to higher frequencies and reaches 2082 cm–1 for 773 K fabricated Co0.3 nm/Pt(111), which has a diffuse (1×1) LEED pattern. We evaluated the dependence of the deposition temperature on the lattice parameters of the Co0.3 nm/Pt(111) and ascribed the band at 2082 cm–1 to adsorbed CO on a Pt-...