Potential-dependent infrared absorption spectroscopy of adsorbed CO and X-ray photoelectron spectroscopy of arc-melted single-phase Pt, PtRu, PtOs, PtRuOs, and Ru electrodes

Journal Article · Thu Apr 20 04:00:00 EDT 2000 · Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical

DOI:https://doi.org/10.1021/jp992943s· OSTI ID:20030677

Liu, R; Iddir, H; Fan, Q ^[1]

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1. and others

The potential- and coverage-dependent infrared absorption spectroscopy (IRAS) of linearly bound CO on single-phase polycrystalline arc-melted Pt, PtRu(1/1), PtRu(8/2), PtRuOs(8/1/1), PtRuOs(65/25/10), and Ru electrodes in 0.5 M H{sub 2}SO{sub 4} are correlated with the potential-dependent X-ray photoelectron spectroscopy (XPS) of the PtRu(1/1), PtOs(8.2), and PtRuOs(65/25/10) substrates. The CO stretching frequencies decrease as the mole fraction of Pt in the alloy is decreased. The CO oxidation onset on pure Pt at 100.0% CO coverage is 0.5 V vs a reversible hydrogen electrode and shifts negatively as the alloy mole fraction of Pt is reduced. At CO dosing conditions that yield 100% coverage on pure Pt, the CO bandwidths increase with decreasing Pt mole fraction: on pure Pt the bandwidths increase as the CO coverage is reduced. The effects of CO coverage and bulk alloy composition on the Stark tuning rates (STRs) have been systematically examined on Pt, and a series of binary and ternary alloy surfaces. The XPS data confirm a potential-dependent surface distribution of oxides and no significant surface segregation of the alloying components. The systematic displacement, to lower frequencies, of the linear STRs as the mole fraction of Pt is reduced suggests no significant island formation on the arc-melted alloy surfaces. The XPS data also suggest that the alloying metals, rather than Pt, are responsible for activation of the water required for methanol oxidation in the direct methanol fuel cell potential window.

• Research Organization: Illinois Inst. of Tech., Chicago, IL (US)
• Sponsoring Organization: US Department of the Army; US Department of Energy
• DOE Contract Number: FG02-91ER45439
• OSTI ID: 20030677
• Journal Information: Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical, Journal Name: Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical Journal Issue: 15 Vol. 104; ISSN 1089-5647; ISSN JPCBFK
• Country of Publication: United States
• Language: English

Related Subjects

30 DIRECT ENERGY CONVERSION
ABSORPTION SPECTROSCOPY
CARBON MONOXIDE
DIRECT METHANOL FUEL CELLS
ELECTRODES
INFRARED SPECTRA
OSMIUM
OXIDATION
PHOTOELECTRON SPECTROSCOPY
PLATINUM
RUTHENIUM