Fundamental Aspects of Spontaneous Cathodic Deposition of Ru onto Pt/C Electrocatalysts and Membranes under Direct Methanol Fuel Cell Operating Conditions
In situ X-ray absorption spectroscopy (XAS), using both EXAFS and the {Delta}{mu}-XANES analysis procedures, is utilized to examine Ru deposition onto Pt/C cathodes at millimolar concentration of Ru in a 1 M HClO{sub 4} electrolyte. Also, electron spin resonance (ESR) spectroscopy is utilized to examine the effects of Ru{sup 3+} ion exchanged Nafion membranes. The {Delta}{mu}-XANES analysis of the data allows a determination of the coverage of Ru with time (minutes to hours) and also to identify the binding site of the deposited Ru species (atop/bridged at low coverage and 3-fold at higher coverage) apparently onto the corners and edges initially and at higher coverage onto the faces of the cubooctahedral clusters when exposed to Ru{sup n+} at OCP. The deposition of Ru appears to be inhibited at potentials where adsorbates (such as H and O(H)) usually adsorb, and Coulomb enhanced at OCP when substantial O exists on the surface. The ESR analysis of Ru{sup 3+} in the Nafion membrane indicates significant detrimental changes to the membrane in the presence of Ru ions; a decrease in the water uptake and an increase in the microviscosity of the fluid regions were noticed. Together these data indicate the critical nature of keeping the fuel cell under potential control and avoiding an uncontrolled shut down under direct methanol operating conditions.
- Research Organization:
- Brookhaven National Lab. (BNL), Upton, NY (United States). National Synchrotron Light Source
- Sponsoring Organization:
- DOE - OFFICE OF SCIENCE
- DOE Contract Number:
- DE-AC02-98CH10886
- OSTI ID:
- 1020127
- Report Number(s):
- BNL-95976-2011-JA; TRN: US201116%%108
- Journal Information:
- Journal of Physical Chemistry C, Vol. 114, Issue 2; ISSN 1932-7447
- Country of Publication:
- United States
- Language:
- English
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