CO monolayer oxidation at Pt(1 0 0) probed by potential step measurements in comparison to Pt(1 1 1) and Pt nanoparticle catalyst

Abstract

The oxidation of CO adsorbed to high coverage on Pt(1 0 0) electrodes in 0.5 M H 2SO 4 is investigated through comparative measurements with Pt(1 1 1). In potential step experiments, current–time transients recorded during CO oxidation on Pt(1 1 1) 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(1 0 0) electrodes than on Pt(1 1 1), and responses for ordered Pt(1 0 0) were close to, but somewhat more complicated than those predicted by the LH model. On Pt(1 0 0) 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(1 0 0) is discussed in terms of properties of Pt(1 0 0)-(1 × 1) islands and possible changes in island size with electrode treatment.