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Kim, Jandee,Lee, Jaesung,Kim, Sechul,Kim, Young-Rae,Rhee, Choong Kyun American Chemical Society 2014 The Journal of Physical Chemistry Part C Vol.118 No.42
<P>This work presents formation of single-layered Pt islands on Au electrodes using the CO route, and the electrochemical behavior of CO, hydrogen, and ethanol was investigated with scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry. The conventional route, consisting of irreversible adsorption of Pt precursor ions (10<SUP>–3</SUP> M PtCl<SUB>4</SUB><SUP>2–</SUP> in 0.05 M H<SUB>2</SUB>SO<SUB>4</SUB>) and subsequent electrochemical reduction, resulted in multiple-layered Pt islands; the CO route, utilizing CO adsorption to protect pre-existing Pt islands from irreversible adsorption of Pt, exclusively produced single-layered Pt islands. Furthermore, STM results implied that single-layered Pt islands on Au(111) were islands of alloyed Pt in a (√3 × √3)<I>R</I>30° arrangement, while multiple-layered islands were stacked layers of Pt in an (1 × 1) array. The coverages of deposited Pt estimated from STM and XPS measurements were quantitatively consistent with each other to confirm existence of the single-layered Pt islands. Coulometric analyses of adsorbed CO and hydrogen indicated lower adsorption stoichiometry of hydrogen on Pt islands prepared by the two deposition routes, especially when the deposited amount of Pt was small. Comparison of the coulometric coverages of CO and hydrogen with electrochemically active Pt coverages estimated with STM results supported that the adsorption stoichiometries of CO and hydrogen were higher on single-layered Pt islands than on multiple-layered ones, roughly by a factor of ∼1.8. Also, ethanol oxidation was enhanced on single-layered Pt islands approximately ∼4 times on average referring to Pt(poly), while the enhancement factor on multiple-layered ones was ∼1.5. Thus, this work demonstrated that the CO route exclusively produced single-layered Pt islands on Au, contrasting with multiple-layered islands in various electrochemical aspects.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2014/jpccck.2014.118.issue-42/jp5062557/production/images/medium/jp-2014-062557_0011.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp5062557'>ACS Electronic Supporting Info</A></P>
Adsorptive Behavior of Dimethylglyoxime on Au(111)
Kim, Jandee,Kim, Sechul,Rhee, Choong Kyun American Chemical Society 2011 Langmuir Vol.27 No.23
<P>Dimethylglyoxime (DMG) adsorbed on Au(111) was investigated using electrochemical scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). STM experiments revealed three different structures of adsorbed DMG at open circuit potential (∼0.07 V versus Ag/AgCl): (2√3×2√3)R30°-α, (2√3×4√3)R30°-β, and (2√3×4√3)R30°-γ. The coverage of adsorbed DMG obtained using XPS was 0.33. A combination of structural and quantitative information identified the adsorbed DMG as an anionic tetramer, held together by intermolecular hydrogen bonding and arrayed in three ordered patterns. Domains of adsorbed DMG underwent phase transitions between the observed structures, most likely due to the influence of the STM tip. However, a significant correlation between the observed structures and the imaging conditions was not found. The ordered layers existed only at open circuit potential as evidenced by their disappearance when the potential was shifted to 0.2 or −0.15 V. The ordered layers were also removed by immersion in a solution of Ni<SUP>2+</SUP>, implying that the adsorbed DMG was converted to a soluble dimer complex with the Ni<SUP>2+</SUP> ion. This particular observation is discussed in terms of the rigidity of the organic network.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/langd5/2011/langd5.2011.27.issue-23/la202594s/production/images/medium/la-2011-02594s_0002.gif'></P>
Kim, Jandee,Shin, Dongwan,Rhee, Choong Kyun,Yoon, Seong-Ho American Chemical Society 2014 Langmuir Vol.30 No.15
<P>This communication compares two different multiple deposition routes of Pt on Au(111), using irreversible adsorption of Pt precursor ions and selective adsorption of CO. A scanning tunneling microscopy study revealed that the conventional route, not utilizing CO, produced multiple-layered Pt cluster islands, while the CO route, employing CO, formed single-layered Pt islands exclusively. The role of CO selectively adsorbed on pre-existing Pt islands was to prevent additional irreversible adsorption of Pt precursor ions onto Pt islands. Cyclic voltammetric works disclosed that the CO and hydrogen coverages on single-layered Pt islands were higher than those on multiple-layered ones, and that the Pt islands on Au were more effective in adsorbing CO than hydrogen.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/langd5/2014/langd5.2014.30.issue-15/la500005p/production/images/medium/la-2014-00005p_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/la500005p'>ACS Electronic Supporting Info</A></P>
Kim, Jandee,Lee, Jeongmook,Youn, Young-Sang,Liu, Nazhen,Kim, Jong-Goo,Ha, Yeong-Keong,Bae, Sang-Eun,Shoesmith, David W.,Kim, Jong-Yun Pergamon Press 2017 Electrochimica Acta Vol. No.
<P><B>Abstract</B></P> <P>The influence of Gd-doping level and oxygen stoichiometry on the structural properties and electrochemical reactivity of U<SUB>1−y</SUB>Gd<SUB>y</SUB>O<SUB>2±x</SUB> have been investigated. The stoichiometry of UO<SUB>2</SUB> matrices with different Gd contents was determined using the lattice parameter obtained by XRD. The extent of lattice contraction, defined by a contraction factor, was found to be dependent on the stoichiometry. The surface morphologies exhibited differences in grain size which varied with stoichiometry and its influence on the U atom diffusivity during fabrication. The differences in grain size and, hence, the density of grain boundaries was reflected in variations in electrical conductivity, with hyperstoichiometric specimens with a low number of boundaries, yielding an increase in conductivity with increasing Gd content. Cyclic voltammetry showed that a variation in Gd content had only a minor influence on the electrochemical reactivity of stoichiometric U<SUB>1−y</SUB>Gd<SUB>y</SUB>O<SUB>2</SUB>. By contrast, the reactivity of hypostoichiometric U<SUB>1−y</SUB>Gd<SUB>y</SUB>O<SUB>2−x</SUB> and hyperstoichiometric U<SUB>1−y</SUB>Gd<SUB>y</SUB>O<SUB>2+x</SUB> increased and decreased, respectively, with increasing Gd content. The formation of Gd-O<SUB>v</SUB> clusters in hyperstoichiometric U<SUB>1−y</SUB>Gd<SUB>y</SUB>O<SUB>2+x</SUB> has a more marked influence on reactivity than the accompanying changes in grain size and electrical conductivity.</P>
Kim, Hye Ryeong,Park, Sunmi,Jung, Changhoon,Kim, Jandee,Rhee, Choong Kyun,Hyun, Moon Seop Royal Society of Chemistry 2010 Chemical communications Vol.46 No.35
<P>Dithiolate-modified multi-wall carbon nanotubes (MWCNTs) adsorb selectively on the self-assembled monolayers (SAMs) of alkanethiols on a Au surface: the long dithiolates attached to the MWCNTs anchor the massive MWCNTs onto the Au surface by replacing the shorter thiolates of SAMs.</P> <P>Graphic Abstract</P><P>The differences in the alkyl chain lengths of the thiolates of SAMs and the dithiolates of MWCNT-S-C<SUB><I>n</I></SUB>-SHs lead to a selective adsorption. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c0cc01148g'> </P>