Surface electrochemistry of CO on Pt(111): Anion Effects
In-situ studies of CO adsorption by surface x-ray scattering (SXS) and Fourier transform infrared (FTIR) spectroscopy techniques are used to create the link between the macroscopic kinetic rates of CO oxidation and the microscopic level of understanding the structure/site occupancy of CO on Pt(111). A remarkable difference in activity was observed between alkaline and acid solutions. In alkaline solution the oxidation of CO proceeds at low overpotential (<0.2 V) by the surface reaction between the adsorbed CO and OH, the latter forming selectively in the hydrogen underpotential potential region at defect sites. In acid solution these sites are blocked by specific adsorption of anions, and consequently in a solution containing Br{sup -} the ignition potential is shifted positively by 0.6 V. Anions of supporting electrolytes also have dramatic effects on both the potential range of stability and the domain size of the p(2x2)-3CO structure which is formed at 0.05 V. The stability/domain size of this structure increases from KOH (ca. 30 {angstrom} between 0.05 < E < 0.3V), to HClO{sub 4} (ca. 140 {angstrom} between 0.05 < E < 0.6V) to HClO{sub 4} + Br{sup -} (ca 350 {angstrom} between 0.05 < E < 0.8V). The larger the ordered domains of the p(2x2)-CO{sub ad} structure are, the less active the surface is towards CO oxidation.
- Research Organization:
- Ernest Orlando Lawrence Berkeley NationalLaboratory, Berkeley, CA (US)
- Sponsoring Organization:
- USDOE Director. Office of Science. Office of Basic EnrgySciences. Materials Sciences Division, Stanford Synchrotron LinearRadiation Laboratory. Division of Chemical Sciences; UK Engineering andPhysical Sciences Research Council
- DOE Contract Number:
- AC02-05CH11231
- OSTI ID:
- 861157
- Report Number(s):
- LBNL--48684
- Journal Information:
- Surface Science Letters, Journal Name: Surface Science Letters Journal Issue: 2-3 Vol. 499
- Country of Publication:
- United States
- Language:
- English
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