title: An NMR determination of CO diffusion on platinum electrocatalysts.
abstract: We report the first direct measurement of CO diffusion on nanoparticle Pt electrocatalysts at the solid/liquid interface, carried out using 13C nuclear magnetic resonance (NMR) with a spin-labeling pulse sequence. Diffusion parameters were measured in the temperature range of 253-293 K for CO adsorbed on commercial Pt-black under saturation coverage. 2H NMR of the same system indicates that the electrolyte remains in the liquid state at temperatures where the CO diffusion experiments were performed. The CO diffusion parameters follow typical Arrhenius behavior with an activation energy of 6.0 +/- 0.4 kcal/mol and a pre-exponential factor of (1.1 +/- 0.6) x 10-8 cm2/s. Exchange between different CO populations, driven by a chemical potential gradient, is suggested to be the main mechanism for CO diffusion. The presence of the electrolyte medium considerably slows down the diffusion of CO as compared to that seen on surfaces of bulk metals under UHV conditions. This work opens up a new approach to the study of surface diffusion of adsorbed molecules on nanoparticle electrode catalysts, including the possibility of correlating diffusion parameters to catalytic activity in real world applications of broad general interest.
authors.affiliation: Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, IL 61801, USA.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kobayashi
authors.forename: Panakkattu K
authors.initials: PK
authors.lastname: Babu
authors.forename: Lajos
authors.initials: L
authors.lastname: Gancs
authors.forename: Jong Ho
authors.initials: JH
authors.lastname: Chung
authors.forename: Eric
authors.initials: E
authors.lastname: Oldfield
authors.forename: Andrzej
authors.initials: A
authors.lastname: Wieckowski
mesh_terms: D002248:Carbon Monoxide / Q000737:chemistry*; D002384:Catalysis; D004058:Diffusion; D004563:Electrochemistry; D009682:Magnetic Resonance Spectroscopy / Q000379:methods* / Q000592:standards; D010984:Platinum / Q000737:chemistry*; D012015:Reference Standards; D013696:Temperature
chemical_list: D010984:Platinum; D002248:Carbon Monoxide