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The Particle Size Dependence of the Oxygen Reduction Reaction for Carbon‐Supported Platinum and Palladium
Author(s) -
Anastasopoulos A.,
Davies J. C.,
Hannah L.,
Hayden B. E.,
Lee C. E.,
Milhano C.,
Mormiche C.,
Offin L.
Publication year - 2013
Publication title -
chemsuschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.412
H-Index - 157
eISSN - 1864-564X
pISSN - 1864-5631
DOI - 10.1002/cssc.201300208
Subject(s) - overpotential , proton exchange membrane fuel cell , catalysis , exchange current density , palladium , platinum , particle size , particle (ecology) , carbon fibers , electrochemistry , chemical engineering , chemistry , inorganic chemistry , electrocatalyst , materials science , electrode , tafel equation , organic chemistry , composite material , oceanography , geology , composite number , engineering
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.