The Interaction of Water with Solid Surfaces: Fundamental Aspects Revisited

Surface science studies of model fuel cell electrocatalysts

Electrocatalysis of methanol oxidation

It is now well-known that the size, shape, and composition of nanomaterials can dramatically affect their physical and chemical properties, and that technologies based on nanoscale materials have the potential to revolutionize fields ranging from catalysis to medicine. Among these materials, anisotropic particles are particularly interesting because the decreased symmetry of such particles often leads to new and unusual chemical and physical behavior. Within this class of particles, triangular Au and Ag nanoprisms stand out due to their structure- and environment-dependent optical features, their anisotropic surface energetics, and the emergence of reliable synthetic methods for producing them in bulk quantities with control over their edge lengths and thickness. This Review will describe a variety of solution-based methods for synthesizing Au and Ag triangular prismatic structures, and will address and discuss proposed mechanisms for their formation.

Colloidal Gold and Silver Triangular Nanoprisms

Underpotential deposition at single crystal surfaces of Au, Pt, Ag and other materials

The spatial structure of compressed carbon monoxide adlayers on Pt(111) in aqueous acidic solution has been explored by means of in‐situ scanning tunneling microscopy (STM) along with infrared reflection–absorption spectroscopy (IRAS). Besides offering a detailed structural picture of this electrochemical interface in comparison with the well‐studied Pt(111)/CO system in ultrahigh vacuum (uhv) environments, the real‐space structural information provided by STM allows an assessment of the obfuscating influence of dynamic dipole coupling upon IRAS binding‐site assignments. In turn, the latter data provide an important crosscheck on the validity of binding‐site assignments deduced from the STM images. Emphasis is placed on the structures formed from near‐saturated CO solutions, encouraged by the electrode potential‐induced adlayer phase transition at ca. 0 V vs SCE observed previously under these conditions by IRAS. At potentials below 0 V, a hexagonal close‐packed (2×2)–3CO adlayer is observed, with a CO co...

Carbon monoxide adlayer structures on platinum (111) electrodes: A synergy between in‐situ scanning tunneling microscopy and infrared spectroscopy

Experimental infrared spectra for CO adlayers on Pt(111) electrodes having known real‐space structures as deduced by scanning tunneling microscopy are compared with predictions extracted from conventional dipole–dipole coupling models in order to test the validity of such treatments for compressed electrochemical adlayers, especially with regard to band‐intensity transfer effects. The specific structures considered are (2×2)–3CO and (√19×√19)R23.4°–13CO hexagonal adlayers; the former is especially close packed (θCO=0.75) with a pair of threefold hollow and one atop CO per unit cell, while the latter has a lower coverage (θCO=13/19) and involves largely asymmetric binding sites. The comparisons between dipole‐coupling theory and experiment include infrared spectra for various 13CO/12CO mixtures, thereby exploiting the well‐known systematic alterations which are induced in the degree of coupling for a given adlayer. Consistent with an earlier assessment (Ref. ) the conventional dipole–dipole treatment can account semiquantitatively for the marked higher intensity of the atop relative to the threefold hollow C–O stretching band in the observed infrared spectra even though the occupancy on the latter site is twofold greater and the singleton frequencies are substantially (∼280 cm−1) different. This coupling‐induced intensity transfer toward the higher‐frequency band component is likely to be a widespread phenomenon for densely packed adlayers.For the (2×2) adlayer, however, the isotope composition‐dependent spectral band frequencies and relative intensities deviate markedly from the experiment. While the inclusion of stochastic broadening effects associated with adlayer disorder improves the situation, a satisfactory fit between theory and experiment requires the incorporation of vibrational coupling associated with short‐range intermolecular interactions. For the (√19×√19) adlayer, on the other hand, dipole–dipole coupling with stochastic broadening accounts well for the observed spectral behavior. The more pronounced limitation of the conventional theory for the (2×2) structure may well be due to the abnormally high adsorbate packing density enhancing the importance of short‐range interactions.

Dipole–dipole coupling effects upon infrared spectroscopy of compressed electrochemical adlayers: Application to the Pt(111)/CO system

The development of a new method for epitaxial growth of compound semiconductors is briefly described: electrochemical atomic layer epitaxy (ECALE). ECALE is based on the successive underpotential deposition (UPD) of atomic layers of different elements to form a compound. Preliminary studies of the ECALE deposition of GaAs were performed in a thin-layer electrochemical cell with a polycrystalline Au electrode. Potentials required for oxidative UPD of As and reductive UPD of Ga were evaluated with different solution concentrations and pH's

Preliminary Studies of GaAs Deposition on Au(100), (110), and (111) Surfaces by Electrochemical Atomic Layer Epitaxy

https://apps.dtic.mil/dtic/tr/fulltext/u2/a276715.pdf

Scanning Tunneling Microscopy and Infrared Spectroscopy as Combined In- Situ Probes of Electrochemical Adlayer Structure: Cyanide on PT(111)

The oxidative chemisorption and cathodic stripping reductive desorption of iodine have been compared at smooth polycrystalline and well-defined Au(111) single-crystal electrodes. Experimental measurements were based upon cyclic voltammetry, thin-layer coulometry, X-ray photoelectron spectroscopy, Auger electron spectroscopy, and low-energy electron diffraction. The results indicate that iodide is oxidatively adsorbed as zerovalent atomic iodine at potentials between −0.4 V and +0.4 V (Ag/AgCl reference); at lower potentials, surface iodine is reductively desorbed as aqueous iodide, while at considerably more positive potentials, it is oxidized to aqueous iodate

Anodic underpotential deposition and cathodic stripping of iodine at polycrystalline and single-crystal gold: studies by LEED, AES, XPS, and electrochemistry

Ignacio Villegas

Papers

Carbon monoxide adlayer structures on platinum (111) electrodes: A synergy between in‐situ scanning tunneling microscopy and infrared spectroscopy

Dipole–dipole coupling effects upon infrared spectroscopy of compressed electrochemical adlayers: Application to the Pt(111)/CO system

Preliminary Studies of GaAs Deposition on Au(100), (110), and (111) Surfaces by Electrochemical Atomic Layer Epitaxy

Scanning Tunneling Microscopy and Infrared Spectroscopy as Combined In- Situ Probes of Electrochemical Adlayer Structure: Cyanide on PT(111)

Anodic underpotential deposition and cathodic stripping of iodine at polycrystalline and single-crystal gold: studies by LEED, AES, XPS, and electrochemistry