In situ atomic force microscopy of underpotential deposition of silver on gold(111)

In situ structural study on underpotential deposition of Ag on Au(111) electrode using surface X-ray scattering technique

“…The charges corresponding to the first, second and third UPD peaks were 100 μC cm -2 , 60 μC cm -2 , and 220 μC cm -2 , respectively, and were exactly the same as those reported by Explandiu et al [19]. Chen et al suggested that peaks C4 and/or C4' were due to a commensurate-incommensurate transition [20]. There is still some controversy on the structure of the UPD layer just before the bulk deposition is started as to whether the monolayer or the bilayer is formed because the total charge of the UPD peaks, 380 μC cm -2 , is more than that of the monolayer, 222 μC cm -2 , but less than that of the bilayers.…”

“…Three dominant cathodic peaks were observed at 520 mV (C1), 130 mV (C2), and 30 mV (C3). These peaks were also observed in most of the previous studies and the positions of these peaks are in good agreement with the ones reported before [14,15,[19][20][21]26]. In addition to these peaks, several small cathodic peaks were also observed at 500 mV (C1'), 330 mV (C4), 240 mV (C4'), and 100 mV (C2').…”

“…The UPD layer with the (1×1) structure was observed just before the bulk deposition was started [14,15,23]. Some groups also found compressed (3 × 3), (5 × 5), and/or (6 × 6) structures before the (1×1) structure was formed [19][20][21]23,24,26].…”

“…Furthermore, the CVs reported by various groups are not necessarily the same and some of the peaks are very small or missing in some cases particularly at the evaporated gold electrode, maybe because the quality of the surface was not high. To clarify the details of each process, a wide variety of techniques such as STM [14][15][16][17][18][19], AFM [20,21], electrochemical quartz crystal microbalance (EQCM) [22], second harmonic generation (SHG) [23], UHV techniques such as low energy electron diffraction (LEED) [21,24], surface extended X-ray absorption fine structure 2 (EXAFS) using X-ray from a synchrotron radiation source [25], and X-ray diffraction (XRD) using a conventional laboratory X-ray source [26,27] have been applied. STM measurements in a sulfuric acid solution showed an ordered (bi)sulfate adlayer with the (√3 × √7)R19.1° structure [19] and the Ag UPD layer with the (√3 × √3)R30° structure [14,15,19] in the potential region more positive and negative, respectively, than the first UPD peak.…”

Electrodeposition of Ag and Pd on a reconstructed Au(1 1 1) electrode surface studied by in situ scanning tunneling microscopy

“…Electrochemical deposition of Ag on Au(111) electrode surface is a good model system to study the morphology of the deposited layer because the interaction and the lattice misfit between a metal deposit and a substrate is very strong and negligibly small (0.4 %), respectively [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] and has been studied by a wide variety of techniques, including scanning tunneling microscopy (STM) [1,2,5,8,9,14,16], atomic force microscopy (AFM) [3,4,6], second harmonic generation (SHG) spectroscopy [13], quartz crystal microbalance (QCM) [7], X-ray diffraction [11,12] and extended X-ray absorption fine structure (EXAFS) [10]. In particular underpotential deposition (UPD) of Ag has received special attention and the structures of adsorbates, both metal and anion, and their dependencies on the potential and electrolyte composition have been well studied [2][3][4][5][6].…”