Underpotential Deposition of Copper on Iodine-Modified Pt(111):  In Situ STM and ex Situ LEED Studies

Abstract

The dynamic process of underpotential deposition (UPD) of copper on iodine-modified Pt(111) electrode in sulfuric acid solution was investigated by in situ scanning tunneling microscopy and ex situ low-energy electron diffraction. Prior to the copper deposition, iodine adlayer structures were characterized by both techniques. It was found that well-ordered iodine adlayers with the structures of (3 × 3) and ( × )R19.1° could be prepared by immersion of the electrode in a solution containing iodide ions under potential control. It was also found that the interconversion of the two structures was very slow. After the UPD of copper on the iodine-modified Pt electrode, the iodine atoms formed a c(p × R-30°) structure with a p value of ca. 2.6 on the (1 × 1) copper adlayer on Pt(111). After the copper was stripped, the electrode exhibited a mixture of (3 × 3) and ( × )R19.1° structures of iodine on Pt(111).

Commensurate monolayers on surfaces: Geometry and ground states

“…The fit of coefficients higher than V ͱ 13G 0 showed that the series eventually converges. Many experimental studies of the I-Pt͑111͒ system show 5,25,26 that there exist two different rigid translational possibilities in the ͑3 ϫ 3͒ cell: sym and asym, both characterized by a perfect hexagonal arrangement inside the unit cell. From our theory, the translational energy Fig.…”

Unequal-sphere packing model for the structural arrangement of the well-ordered adsorbate-substrate system

“…It is the so-called ͑3 ϫ 3͒-asym structure. [24][25][26][27][28][29][30][31][32][33][34][35][36][37]41,42 We believe that our model based on geometrical principles can also explain the appearance of this particular structure. Note that the arrangement of ͑3 ϫ 3͒-asym iodine adlayer on Pt(111) has been described in many papers, so far.…”

“…In case of ͑3 ϫ 3͒-asym, each threefold iodine atoms is surrounded by six neighboring adatoms positioned at a higher level. [24][25][26][27][28][29][30][31][32][33][34][35][36][37] In order to understand the conditions for appearance and differences between ͑3 ϫ 3͒-sym and ͑3 ϫ 3͒-asym structures we employ our model, looking for a full range of possible FIG. 4.…”

Detailed characterization of (3×3) iodine adlayer on Pt(111) by unequal-sphere packing model

“…These lattices have been characterized by LEED, [6][7][8][9][10][11][12] ADAM, 13 STM, [14][15][16] and Surface X-ray Scattering ͑SXS͒. [17][18][19][20][21] The same type of iodine adlayer on Pt͑111͒ was found for preparations from gas phase [12][13][14] and from aqueous solution.…”

“…[17][18][19][20][21] The same type of iodine adlayer on Pt͑111͒ was found for preparations from gas phase [12][13][14] and from aqueous solution. [6][7][8][9][10][11]15,16 Experimental data also show that an iodine adlayer with ͑3 ϫ 3͒ unit cell structure can form two distinct lattices, 10,[13][14][15][16] in which iodine-iodine interatomic distance ͑4.162 Å͒ and surface coverage are the same, but iodine adatoms possess different registries. They are known as the ͑3 ϫ 3͒-sym and ͑3 ϫ 3͒-asym adlattices.…”