Electrochemical studies of carbon monoxide oxidation on platinum and platinum based fuel cell catalysts

Electrochemical studies of carbon monoxide (CO) oxidation on surfaces of bulk platinum (Pt) and Pt based particle catalysts were conducted. Investigations focused on understanding relationships between surface characteristics of Pt electrodes and the oxidation kinetics of monolayer quantities of adsorbed CO. Cyclic voltammetry and potential step chronoamperometry measurements performed on the bulk polycrystalline Pt, Pt(111), Pt(s)-[4(111) x (100)] ß Pt(335) and Pt(s)-[6(111) x (100)] ß Pt(557) electrodes in 0.1 M HClO4 and 0.1 M H2SO4 electrolyte solutions showed the consistent trend of increasing CO oxidation rate with increasing density of steps, or low atomic coordination surface sites. Current-time transients could be fit to a Langmiur-Hinshelwood (LH) type mean field kinetic model. Responses obtained in experiments with the single crystal electrodes were consistent with literature reports for structurally related Pt surfaces and were used as benchmarks to verify system cleanliness in subsequent measurements with nanometer- cale metal catalyst particles. Two strategies were employed for the study of Pt based nanoparticles. In one approach, prepared catalyst was immobilized by adsorption onto the surface of a polycrystalline gold (Au) electrode. Electrochemical properties of the catalyst materials were examined over a range of potentials that spanned the double layer region of Au. In a second approach, particles were formed by electrochemical reduction onto the surface of a glassy carbon or a highly ordered graphite (HOPG) electrode. In the case of HOPG, additional characterization of the particles was performed by atomic force microscopy (AFM) measurements. The electrochemistry of CO on Pt catalyst particles was similar to responses for CO on polycrystalline Pt. However, current-time transients recorded in potential step chronoamperometry experiments displayed deviations from the mean field LH mechanism; tailing was observed at long times in the transients. Methods employed for the study of prepared catalyst on Au electrodes were extended to investigate nanometer-scale PtIr and PtFe catalyst. Procedures were developed for the removal of stabilizing ligands and the activation of the metal surfaces. The bimetallic materials were active toward the oxidation of CO and CH3OH.

Author dc:creator

• Zhou, Wei

• platinum fuel based cell catalysts
• carbon monoxide oxidation
• platinum

Language dc:language.iso

en

Handle dc:identifier.uri

https://hdl.handle.net/2346/107667

OAI identifier oai:identifier

oai:ttu-ir.tdl.org:2346/107667