title: The particle size dependence of the oxygen reduction reaction for carbon-supported platinum and palladium.
abstract: Model carbon supported Pt and Pd electrocatalysts have been prepared using a high-throughput physical vapor deposition method. For Pt, metal particle sizes are controlled between 1.5-5.5 nm over 100 electrodes of an electrochemical screening chip, allowing the oxygen reduction reaction (ORR) activity of the catalysts to be determined simultaneously. The ORR-specific current density is observed to increase with increasing particle diameter up to approximately 4 nm, at which point the activity begins to level off. The reduction in ORR activity for particles below 4 nm is accompanied by a concomitant increase in the overpotential for surface reduction. The resulting mass activity exhibits a maximum for particles with diameters of approximately 3.5 nm. These results are consistent with results published recently for high area carbon-supported Pt catalysts. For Pd particles, both the specific current density and the mass-specific activity for the ORR are observed to increase with increasing particle diameter, with no distinct optimum observed. The implications for the optimization of Pt- or Pd-based ORR catalysts for proton exchange membrane fuel cell (PEMFC) applications are discussed.
authors.affiliation: School of Chemistry, University of Southampton, Southampton, Hampshire, SO16 7NS (United Kingdom).
authors.forename: A
authors.initials: A
authors.lastname: Anastasopoulos
authors.forename: J C
authors.initials: JC
authors.lastname: Davies
authors.forename: L
authors.initials: L
authors.lastname: Hannah
authors.forename: B E
authors.initials: BE
authors.lastname: Hayden
authors.forename: C E
authors.initials: CE
authors.lastname: Lee
authors.forename: C
authors.initials: C
authors.lastname: Milhano
authors.forename: C
authors.initials: C
authors.lastname: Mormiche
authors.forename: L
authors.initials: L
authors.lastname: Offin
mesh_terms: D002244:Carbon / Q000737:chemistry*; D004563:Electrochemistry; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*; D010165:Palladium / Q000737:chemistry*; D010316:Particle Size; D010984:Platinum / Q000737:chemistry*
chemical_list: D010984:Platinum; D010165:Palladium; D002244:Carbon; D010100:Oxygen
keywords: high-throughput; oxygen reduction reaction; palladium; particle size dependence; platinum