The effect of the cooling atmosphere in the preparation of flame-annealed Pt(111) electrodes on CO adlayer oxidation

The effect of the cooling atmosphere on the rate of CO adlayer oxidation on flame-annealed Pt( 111) has been studied. Cooling of a flame-annealed Pt(1 11) electrode in air results in a higher amount of crystalline defects comp ared to Pt(111) cooled in a hy-drogen-argon stream. Although the blank prof iles in 0.5 M H2SO4 of Pt(111), cooled in air and under oxygen exclusion, a re virtually identical, CO adlayer oxidation occurs at significantly lower overpotentials on the former electrode. Three voltammetric peaks are observ ed for subsaturated CO adlayer oxidation on Pt(111), cooled in Ar+H-2 mixtu re, while only two peaks develop in the case of a Pt(111) surface cooled in air. Random crystalline defects, introduced via cooling of a flame-anneale d Pt(111) in air, enhance CO adlayer oxidation, and apparently also suppres s the third high-potential peak observed on a quasi-perfect (111) surface. The high sensitivity of the saturated CO adlayer oxidation to the presence of crystalline defects on Pt(111) can hence be used as a straightforward, s ensitive, though qualitative method to assess the degree of crystalline ord er of the electrode. (C) 2000 Elsevier Science S.A. All rights reserved.