Abstract
We outline a systematic experimental and theoretical study on the influence of ruthenium contamination on the oxygen reduction activity (ORR) of a Pt/C catalyst at potentials relevant to a polymer electrolyte fuel cell cathode. A commercial Pt/C catalyst was contaminated by different amounts of ruthenium, equivalent to 0.15–4 monolayers. The resulting ruthenium-contaminated Pt/C powders were characterized by energy–dispersive x–ray spectroscopy (EDS), x–ray photoelectron spectroscopy (XPS) and scanning transmission electron microscopy (STEM) to verify ruthenium contamination. A rotating disk electrode (RDE) technique was used to study the influence of ruthenium on oxygen reduction kinetics. Density functional theory (DFT) calculations were performed to estimate the oxygen reduction activity of the platinum surface with increasing ruthenium coverage, simulating ruthenium-contaminated Pt/C. The binding energies of O and OH on the surfaces were used for activity estimations. It was found that the specific activity of the ORR at 0.85 V vs RHE exhibited an exponential-like decay with increased ruthenium contamination, decreasing by ∼45% already at 0.15 monolayer-equivalent contamination. The results of the DFT calculations were qualitatively in line with experimental findings, verifying the ability of the chosen approach to predict the effect of ruthenium contamination on ORR on platinum.
Highlights
Hydrogen-fed Polymer Electrolyte Membrane Fuel Cells (PEMFCs) and their closely related Direct Methanol Fuel Cells (DMFCs) are considered to be promising energy generators for electric vehicles (EVs), backup or off-grid power and mobile electronic devices [1, 2]
Suspecting that the agglomeration was caused by exposure to hot reflux during the synthesis, a suspension containing HiSPEC8000 and methanol but not ruthenium salt was refluxed for the same time as during ruthenium deposition
In this work we studied the effect of ruthenium contamination on ORR on platinum, focusing on the implications on PEMFC and DMFC cathode-relevant potentials
Summary
Hydrogen-fed Polymer Electrolyte Membrane Fuel Cells (PEMFCs) and their closely related Direct Methanol Fuel Cells (DMFCs) are considered to be promising energy generators for electric vehicles (EVs), backup or off-grid power and mobile electronic devices [1, 2]. Ruthenium dissolution from the anode catalyst results in a loss of ruthenium and changes to its Pt:Ru ratio This change leads to reduced CO tolerance and methanol oxidation activity [10] of the catalyst (for reformate-based PEMFCs and DMFCs, respectively) that will translate to higher overpotentials of the anode [11]. Various and precisely known amounts of ruthenium were deposited on platinum by electroless deposition at 90°C with methanol as the reducing agent This resulted in Pt/C catalysts contaminated with different coverage levels of ruthenium. This deposition method was chosen to mimic the existing conditions in a DMFC cathode (approximated working temperature and presence of methanol which had crossed from the anode).
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
