CO monolayer oxidation at Pt(100) probed by potential step measurements in comparison to Pt(111) and Pt nanoparticle catalyst

The oxidation of CO adsorbed to high coverage on Pt(100) electrodes in 0.5 M H2SO4 is investigated through comparative measurements with Pt(111). In potential step experiments, current-time transients recorded during CO oxidation on Pt(111) display the same peak times and adherence to a Langmuir-Hinshelwood (LH) model for adsorbed CO electrochemical oxidation as literature benchmarks. For potentials in the vicinity of 0.8-0.9 V (versus a reversible hydrogen electrode reference), CO oxidation was faster on ordered Pt(100) electrodes than on Pt(111), and responses for ordered Pt(100) were close to, but somewhat more complicated than those predicted by the LH model. On Pt(100) with defects intentionally introduced by eliminating H-2 gas from the cooling atmosphere, current-time transients recorded during CO monolayer oxidation showed tailing at long times and responses similar to those for the reaction over nanometer-scale (< 10 nm) Pt catalyst particles. The kinetics for CO monolayer oxidation on Pt(100) is discussed in terms of properties of Pt(100)-(1 x 1) islands and possible changes in island size with electrode treatment. (c) 2007 Elsevier B.V. All rights reserved.