Structure of Chemisorbed Sulfur on a Pt(111) Electrode

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• 作者：Y.-E. Sung ; W. Chrzanowski ; A. Zolfaghari ; G. Jerkiewicz ; and A. Wieckowski
• 刊名：Journal of the American Chemical Society
• 出版年：1997
• 出版时间：January 8, 1997
• 年：1997
• 卷：119
• 期：1
• 页码：194 - 200
• 全文大小：220K
• 年卷期：v.119,no.1(January 8, 1997)
• ISSN：1520-5126

文摘

Electron spectroscopic and diffraction results obtained inultra-high-vacuum, combined with cyclicvoltammetric data, are reported for sulfur adlayers deposited fromaqueous sulfide and bisulfide media on Pt(111).The highest coverage obtained by Auger electron spectroscopy, 0.94± 0.05 monolayer, is very close to the coverageobtained from coulometry, and is associated with a (1×1) surfacephase. This coverage is much higher than thatobtained in previous electrochemical studies but is the same as foundby other investigators using S₂ beam dosingin vacuum. The near complete sulfur monolayer is characterized bya rapid and incomplete oxidation in a narrowpotential range near 0.70 V vs a Ag/AgCl reference. Neither fullsulfur monolayer coverage nor a sharp voltammetrictransition could be obtained when traces of oxygen were present in theelectrochemical cell. Oxidation of the (1×1)adlayer (at mages/entities/ap.gif">1 monolayer) gave rise to a previously unreported(2×2) structure, at ¹/₂ monolayer.Further voltammetricstripping resulted in two more adlattices:(mages/entities/radic.gif">3×mages/entities/radic.gif">3)R30mages/entities/deg.gif"> at ¹/₃monolayer and p(2×2) at ¹/₄ monolayer, asreportedin previous gas phase studies. The selective stripping procedureprovides unique electrochemical control at roomtemperature of surface structure and coverage, without any change inthe long-range surface order of the substrate.When dosing was carried out from bisulfide solution, a(mages/entities/radic.gif">3×mages/entities/radic.gif">7) phase at ³/₅ monolayer wasformed, which onceagain was not reported previously. The results of the core-levelelectron energy loss spectroscopy studies suggestthat sulfur adatoms retain some of the negative charge and that thischarge plays a major role in controlling hydrogenadsorption coverage in the presence of coadsorbed sulfur onPt(111).