Bimetallic electrodes are used in a number of electrochemical processes, but the role particular arrangements surface metal atoms (ensembles) has not been studied directly. We have evaluated electrochemical/catalytic properties defined atomic ensembles atomically flat PdAu(111) with variable stoichiometry that were prepared by controlled electrodeposition on Au(111). These derived from infrared spectroscopic and voltammetric data obtained for electrode surfaces which concentration...

The atomic structure of ordered Cu adsorbate layers on Au(111) and Au(100) electrode surfaces the clean substrates was resolved in scanning tunneling microscopy images taken situ. For submonolayer coverages deposited from sulfuric acid solutions under potential control, various structures were observed. quasihexagonal arrangement atoms these reflects increasingly repulsive interactions between closely spaced adatoms. These differ pseudomorphic adlayer formed vacuum conditions, which...

Abstract Convoluted selectivity trends and a missing link between reaction product distribution catalyst properties hinder practical applications of the electrochemical CO 2 reduction (CO RR) for multicarbon generation. Here we employ operando X-ray absorption diffraction methods with subsecond time resolution to unveil surprising complexity catalysts exposed dynamic conditions. We show that by using pulsed protocol consisting alternating working oxidizing potential periods dynamically...

For the knowledged-based development of electrochemical processes, a better fundamental understanding interfaces between electrodes and electrolytes is necessary. This requires insight into interface structure dynamics on atomic-scale, including that liquid electrolyte in near-surface region, i.e., inner outer part double layer. perspective describes current studies simple well-defined by first-principles electronic calculations situ structure-sensitive methods. It shown these experimental...

Abstract Potentiodynamic methods that induce structural changes in Cu catalysts for the electrochemical reduction of CO 2 (CO RR) have been identified as a promising strategy steering catalyst selectivity towards generation multi-carbon products. In current approaches, active species are created via sequential oxidation–reduction process. Here we show by situ scanning tunnelling microscopy, surface X-ray diffraction and Raman spectroscopy measurements low-coordinated form spontaneously near...

The surface normal structure of the mercury liquid-vapor interface has been investigated by measuring x-ray reflectivity out to a momentum transfer ${q}_{z}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}2.5$ ${\mathrm{\AA{}}}^{--1}$. results provide direct experimental proof layering in liquid metals. layer spacing is given atomic dimensions Hg atoms. minimum width agrees well with predictions capillary wave theory; amplitude decays into bulk characteristic length 3--3.5 \AA{}, which...

The oxidation of liquid-gallium surfaces has been investigated with surface x-ray scattering techniques. By exposing the liquid-metal at room temperature to doses on order 180 L oxygen where 1 L=${10}^{\mathrm{\ensuremath{-}}6}$ Torr s, a gallium oxide film well-defined thickness \ensuremath{\sim}5 \AA{} readily forms. and roughness liquid/oxide oxide/vapor interfaces do not change dosage up 1600 nor 573 K. This is in contrast what observed for bare liquid-Ga surface, which roughened...

Surface-induced atomic layering in liquid gallium has been observed using x-ray reflectivity, ultrahigh vacuum conditions, and sputtered clean surfaces. Reflectivity data, collected on a supercooled sample to momentum transfers as large ${q}_{z}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}3.0{\AA{}}^{\ensuremath{-}1}$, exhibit strong maximum near 2.4 \AA{} ${}^{\ensuremath{-}1}$ indicating layer spacing that is comparable its dimensions. The amplitude of the electron density...

In situ scanning tunnelling microscopy (STM) studies on Au(111) in H2SO4 solutions are presented which resolve an ordered structure the adsorbate layer with a ([graphic omitted]) unit cell and coverage of 0.4 monolayers at potentials above ca. 0.75 V vs. SCE. From absence this Na2SO4 we conclude that is hydrogensulfate species. The abrupt disorder-order phase transition SCE coincides sharp peak voltammogram, underlining influence adlayer structural effects voltammogram. proceeds fast...

A modular system has been developed to mount molecules upright onto metal surfaces in a well controlled geometry. The approach is based on reactive platform (triazatriangulenium salt) with an electrophilic center. Functional are attached via C-C bond formation. distance from the surface can be varied by spacer, and of functional units each other size platform. Self-assembly parent triazaangulenium salt as functionalized platforms Au(111) results stable, hexagonally ordered adlayers.

Room-temperature ionic liquids are of great current interest for electrochemical applications in material and energy science. Essential understanding the reactivity these systems detailed data on structure dynamics interfaces between compounds metal electrodes, which distinctly differ from those traditional electrolytes. In situ studies presented Au(111) electrodes 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([BMP][TFSA]) by high-speed scanning tunneling microscopy...

The new third-generation synchrotron radiation source PETRA III located at the Deutsches Elektronen-Synchrotron DESY in Hamburg, Germany, has been operational since second half of 2009. is designed to deliver hard X-ray beams with very high brilliance. As one first beamlines high-resolution diffraction beamline P08 fully operational. specialized scattering and experiments on solids liquids where extreme resolution reciprocal space required. resolving power results high-quality beam unique...

In the search for precious-metal-free electrode materials electrochemical water splitting, transition-metal oxides have been receiving much recent interest as active and stable electrocatalysts anodic oxygen evolution reaction (OER). We present operando surface X-ray diffraction studies of two structurally well-defined epitaxial cobalt oxide thin films: Co3O4(111) CoOOH(001) electrodeposited on Au(111). The potential-dependent structural changes during cyclic voltammograms were monitored...

The surface restructuring of Pt(111) electrodes upon electrochemical oxidation/reduction in 0.1 M HClO4 was studied by situ grazing-incidence small-angle X-ray scattering and complementary scanning tunneling microscopy measurements. These methods allow quantitative determination the formation structural evolution nanoscale Pt islands during potential cycles into oxidation region. A characteristic ripening behavior is observed, where these become more prominent homogeneous size with...

Co oxides and oxyhydroxides have been studied extensively in the past as promising electrocatalysts for oxygen evolution reaction (OER) neutral to alkaline media. Earlier studies showed formation of an ultrathin CoO x (OH) y skin layer on Co3O4 at potentials above 1.15 V vs reversible hydrogen electrode (RHE), but precise influence this OER reactivity is still under debate. We present here a systematic study epitaxial spinel-type films with defined (111) orientation, prepared different...

The degradation of Pt-containing oxygen reduction catalysts for fuel cell applications is strongly linked to the electrochemical surface oxidation and Pt. Here, we study restructuring Pt dissolution mechanisms during oxidation/reduction case Pt(100) in 0.1 M HClO4 by combining operando high-energy X-ray diffraction, online mass spectrometry, density functional theory. Our atomic-scale structural studies reveal that anodic dissolution, detected oxidation, cathodic observed subsequent...

We have investigated submonolayer electrodeposits of copper on the three low-index planes gold in situ by STM. The atomic structure clean electrode surfaces and different ordered Cu adsorbate layers were resolved. For coverages Au(111) Au(100), deposited under potential control from sulfuric acid solutions, various structures observed, where adatoms are arranged hexagonal or quasihexagonal lattices. larger Cu-Cu distances these structures, as compared to pseudomorphic (1×1) islands formed...

We present in situ surface x-ray scattering observations of ordered chloride and bromide monolayers on Au(111) electrodes aqueous solutions as an example diffraction from adsorbates the lighter elements (Z50). At a critical density both halides form incommensurate, hexagonal-close-packed that compress uniformly with increasing potential. Our structural results provide quantitative data residual adsorbate charge, two-dimensional melting, compressibilities halide monolayers.

Surface-induced atomic layering at the liquid/vapor interface in liquid metals has been observed using x-ray reflectivity on sputtered clean surfaces under ultrahigh vacuum conditions. A well-defined quasi-Bragg peak is obtained for of elemental Ga and a Ga-In alloy large wave vectors ${\mathrm{q}}_{\mathrm{z}}$\ensuremath{\sim}2.3--2.5 ${\mathrm{\AA{}}}^{\mathrm{\ensuremath{-}}1}$. These results are an unambiguous indication with interlayer spacing...

Electrochemical hydrogen evolution on (100)-oriented copper electrodes is shown to induce a novel surface reconstruction, which substantially influences the rates of this electrochemical reaction. As revealed by in situ video-STM formation phase starts with lateral displacements Cu atoms from lattice positions, resulting stripe-like structures, followed expansion along stripe direction.