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The Oxidation Behaviour of Ruthenium in the Presence of Platinum and its Effect on the Electrocatalytic Activity of Pt-Ru Fuel Cell Catalysts

  • C. Roth , N. Benker , S. Zils , R. Chenitz , A. Issanin and Hartmut Fuess
Published/Copyright: September 25, 2009
Zeitschrift für Physikalische Chemie
From the journal Zeitschrift für Physikalische Chemie Volume 221 Issue 11-12

Pt-Ru electrocatalysts are commonly applied anode materials for low-temperature fuel cells, as the addition of ruthenium improves the CO tolerance of the otherwise CO-sensitive platinum catalysts, either by an electronic effect or by electro-oxidation via oxygen-containing adsorbates in the so-called bifunctional mechanism. However, since bulk ruthenium oxidation already takes place at potentials of less than 1.0V vs. RHE and hydrous ruthenium oxide is suggested to be the active species in the bifunctional mechanism, the amount and specific nature of ruthenium oxides play an important role in fuel cell catalysis. Two Pt-Ru catalyst systems with distinctly different Pt-Ru separation have been studied: a carbon-supported Pt-Ru alloy electrocatalyst (Pt-Ru) and a mixture of carbon-supported Pt and carbon-supported Ru (Pt/Ru). Controlled heat-treatment experiments were carried out in air atmosphere at 100°C and 500°C to study the effect of deliberate ruthenium oxidation on the catalyst structure and electrochemical performance. At a heat-treatment temperature of 100°C, the Pt-Ru alloy appears less sensitive towards oxidation than the Pt/Ru mixture, although its lattice parameter increases from about 3.880Å to 3.907Å indicating that part of the ruthenium is pulled out of the alloy phase to form a (amorphous) ruthenium oxide. After heat-treatment at 500°C in air, X-ray patterns of the Pt-Ru alloy and the Pt/Ru mixture look almost alike. However, transmission electron micrographs reveal a distinctly different separation between the Pt and the Ru oxide phase with the Pt-Ru alloy system having many more Pt/Ru neighbour sites available. Complementary XPS measurements show a higher share of electrocatalytically inactive ruthenium oxide in the Pt/Ru mixture catalyst heat-treated at 100°C. The onset of the methanol oxidation reaction (MOR) for the different catalysts increases in the order Pt-Ru < Pt/Ru < Pt independent of the treatment underlining the importance of Pt/Ru site distribution and ruthenium oxide content for the electrocatalytic activity.

Keywords: Electrocatalysis; Heat-Treatment; Methanol Oxidation (MOR); Pt-Ru Ruthenium Oxide
Received: 2007-8-9
Accepted: 2007-8-31
Published Online: 2009-9-25
Published in Print: 2007-12-1

© Oldenbourg Wissenschaftsverlag

Articles in the same Issue

  1. Preface: Für Konrad Georg Weil
  2. IR Voltage in Crevices during Crevice Corrosion and Sacrificial Cathodic Protection
  3. Synthesis of Zirconium Nanoparticles by Ultrafast Laser Ablation
  4. Resistive Switching in Ge0.3Se0.7 Films by Means of Copper Ion Migration
  5. Microcalorimetry of Electrochemical Reactions at Submonolayer Conversions
  6. On a New Phase Transition in the Cu/Au(111)/H2SO4 System
  7. In Situ Investigations on the Oxidation of Metals
  8. A High-Temperature Mössbauer Study of the Iron Nitrides
  9. Characterization of V-W and Mo-W Mixed Oxide Catalysts for the Selective Oxidation of Acrolein to Acrylic Acid
  10. The Oxidation Behaviour of Ruthenium in the Presence of Platinum and its Effect on the Electrocatalytic Activity of Pt-Ru Fuel Cell Catalysts
  11. Surface-Induced Dissociation as a Probe for the Energetics and Structure of Lead Clusters
  12. High Resolution FTIR and Diode Laser Supersonic Jet Spectroscopy of the N = 2 HF Stretching Polyad in (HF)2 and (HFDF): Hydrogen Bond Switching and Predissociation Dynamics
  13. A Refined All-Atom Model for the Ionic Liquid 1-n-Butyl 3-Methylimidazolium bis(Trifluoromethylsulfonyl)imide [bmim][Tf2N]
  14. A First-Principles Investigation of the Electronic Structure of Trivalent Rare Earth Ions in Gallium Nitride
https://doi.org/10.1524/zpch.2007.221.11-12.1549
Keywords for this article
Electrocatalysis; Heat-Treatment; Methanol Oxidation (MOR); Pt-Ru Ruthenium Oxide

Articles in the same Issue

  1. Preface: Für Konrad Georg Weil
  2. IR Voltage in Crevices during Crevice Corrosion and Sacrificial Cathodic Protection
  3. Synthesis of Zirconium Nanoparticles by Ultrafast Laser Ablation
  4. Resistive Switching in Ge0.3Se0.7 Films by Means of Copper Ion Migration
  5. Microcalorimetry of Electrochemical Reactions at Submonolayer Conversions
  6. On a New Phase Transition in the Cu/Au(111)/H2SO4 System
  7. In Situ Investigations on the Oxidation of Metals
  8. A High-Temperature Mössbauer Study of the Iron Nitrides
  9. Characterization of V-W and Mo-W Mixed Oxide Catalysts for the Selective Oxidation of Acrolein to Acrylic Acid
  10. The Oxidation Behaviour of Ruthenium in the Presence of Platinum and its Effect on the Electrocatalytic Activity of Pt-Ru Fuel Cell Catalysts
  11. Surface-Induced Dissociation as a Probe for the Energetics and Structure of Lead Clusters
  12. High Resolution FTIR and Diode Laser Supersonic Jet Spectroscopy of the N = 2 HF Stretching Polyad in (HF)2 and (HFDF): Hydrogen Bond Switching and Predissociation Dynamics
  13. A Refined All-Atom Model for the Ionic Liquid 1-n-Butyl 3-Methylimidazolium bis(Trifluoromethylsulfonyl)imide [bmim][Tf2N]
  14. A First-Principles Investigation of the Electronic Structure of Trivalent Rare Earth Ions in Gallium Nitride
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