Adsorbed thiophenol and related compounds studied at Pt(111) electrodes by EELS, Auger spectroscopy, and cyclic voltammetry

Journal Article · Wed Jul 20 04:00:00 EDT 1988 · Journal of the American Chemical Society; (USA)

DOI:https://doi.org/10.1021/ja00223a003· OSTI ID:5656503

Stern, D A; Wellner, E; Salaita, G N; Laguren-Davidson, L; Lu, F; Batina, N; Frank, D G; Zapien, D C; Walton, N; Hubbard, A T ^[1]

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1. Univ. of Cincinnati, OH (USA)

Adsorption of the following compounds from aqueous solutions at well-defined Pt(111) single-crystal surfaces has been studied: 2,5-dihydroxythiophenol (DHTP); 2,5-dihydroxy-4-methylbenzyl mercaptan (DMBM); thiophenol (TP); pentafluorothiphenol (PFTP); 2,3,5,6-tetrafluorothiphenol (TFTP4); 2,3,4,5-tetrafluorothiophenol (TFTP2); and benzyl mercaptan (BM). Adsorbed layers formed from DHTP or DMBM were found by cyclic voltammetry to undergo reversible two-electron, two-proton electrochemical oxidation-reduction and were shown to be stable under vacuum. Therefore, the results of surface spectroscopy in ultrahigh vacuum are directly applicable to the liquid-solid and vapor-solid chemistry and electrochemistry of these compounds. Packing density (adsorbed moles per unit area) was measured for each compound by quantitative Auger electron spectroscopy. Vibrational spectra of the adsorbed layers from these compounds were obtained by electron energy-loss spectroscopy (EELS) and were compared with the infrared (IR) spectra of the parent compounds in KBr. The EELS and IR spectra were quite similar except that the mercaptan hydrogen is lost during adsorption, and EELS de-emphasizes the O-H stretching modes of phenolic compound such as DHTP and DMBM. Each of these compounds is evidently attached to Pt(111) predominantly through the sulfur atom. LEED observations reveal that, except for the DMBM layer which has (2{radical}3 {times} 2{radical}3)R30{degree}C symmetry, these compounds adsorb without long-range ordering with respect to the Pt(111) surface, although their large, constant packing density and attachment through the S atom is evidence that the adsorbed molecules are uniformly oriented. 15 references, 10 figures, 4 tables.

• OSTI ID: 5656503
• Journal Information: Journal of the American Chemical Society; (USA), Journal Name: Journal of the American Chemical Society; (USA) Vol. 110:15; ISSN 0002-7863; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ADSORPTION
AROMATICS
CHEMISTRY
CRYSTALS
DATA
ELECTROCHEMISTRY
ELECTRODES
EXPERIMENTAL DATA
HYDROXY COMPOUNDS
INFORMATION
MONOCRYSTALS
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
PHENOLS
PLATINUM COMPOUNDS
SORPTION
THIOLS
TRANSITION ELEMENT COMPOUNDS