Re-Examination of the Pt Particle Size Effect on the Oxygen Reduction Reaction for Ultrathin Uniform Pt/C Catalyst Layers without Influence from Nafion

Kazuma Shinozaki, Bryan Pivovar, Yu Morimoto, Shyam Kocha

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44 Scopus Citations

Abstract

The platinum ‘particle size effect’ on the oxygen reduction reaction (ORR) has been re-evaluated using commercial Pt/C catalysts (2–10 nm Pt particle) and polycrystalline Pt (poly-Pt) in 0.1 M HClO4 with a rotating disk electrode method. Nafion-free catalyst layers were employed to obtain specific activities (SA) that were not perturbed (suppressed) by sulfonate anion adsorption/blocking. By using ultrathin uniform catalyst layers, O2 diffusion limitation was minimized as confirmed from the high SAs of our supported catalysts that were comparable to unsupported sputtered Pt having controlled sizes. The specific activity (SA) steeply increased for the particle sizes in the range ∼2–10 nm (0.8–1.8 mA/cm2Pt at 0.9 V vs. RHE) and plateaued over ∼10 nm to 2.7 mA/cm2Pt for bulk poly-Pt. On the basis of the activity trend for the range of particle sizes studied, it appears that the effect of carbon support on activity is negligible. The experimental results and the concomitant profile of SA vs. particle size was found to be in an agreement to a truncated octahedral particle model that assumes active terrace sites.

Original languageAmerican English
Pages (from-to)783-790
Number of pages8
JournalElectrochimica Acta
Volume213
DOIs
StatePublished - 20 Sep 2016

Bibliographical note

Publisher Copyright:
© 2016 Elsevier Ltd

NREL Publication Number

  • NREL/JA-5900-66975

Keywords

  • Nafion-free activity
  • Oxygen reduction reaction
  • Particle size effect
  • Platinum
  • Rotating disk electrode method

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