The full 3D structure of a copper/electrolyte interface is studied by means of in situ surface X-ray diffraction (SXRD) methods. Chloride anions chemisorb on Cu(100) in 10 mM HCl at high potentials under formation of a p(1 × 1)-Cl adlayer. This anionic chemisorption layer serves as a structural template for the lateral ordering of water molecules and hydronium cations in the near-surface liquid electrolyte. Evidence for this interfacial geometry is mainly derived from the intensity distribution of surface-sensitive X-ray diffraction data along the (10L)-adlayer rod. The characteristic oscillating intensity distribution along the (10L) rod is due to a centered bilayer system consisting of the anionic inner Helmholtz layer (IHL) of chemisorbed chloride and the cationic outer Helmholtz layer (OHL). The latter is constituted in the present case by hydronium cations that preferentially populate 4-fold hollow sites of the underlying chloride lattice. IHL and OHL are separated by an extra interfacial water layer. Anions and cations in the IHL and OHL compete for these water species as part of their solvation shell. The Cl/water/hydronium bilayer can be considered as a prototypical model system where the anions and cations in the coupled bilayer system are sharing the interfacial water as part of their solvation shell. In this respect, the Cl − /water/hydronium bilayer considerably differs from the previously studied Cl − /water/K + system where the interfacial water was clearly assigned to the solvation shell of the alkali metal cation in the OHL. The absence of strongly solvated alkali metal cations in the OHL leads to an increase in the in-plane and out-of-plane exchange dynamics of water and hydronium cations as manifested by an isotropic atomic displacement parameter that is notably higher for the Cl − /water/hydronium than for the more static Cl − /water/K + system. A comprehensive comparison of our results with other state-of-the-art SXRD studies strongly suggests that the adsorption of partly solvated cations on-top of an anionmodified metal electrode surface has to be considered as a specif ic cation adsorption phenomenon since the particular structure of the formed bilayer system as well as the involved interfacial dynamics clearly depend on the chemical nature of the anions and cations involved in the structure formation.
Charged organic adsorbates play an important role in a number of electrochemical reactions, e.g. as additives for metal plating relevant for device fabrication in the semiconductor industry. Fundamental investigations are mandatory in order to acquire profound knowledge of the
structural and electronic properties of these layers parallel and perpendicular to the surface, and to finally achieve a deeper mechanistic understanding of the kinetics of involved charge transfer reactions taking place at these complex metal/organic/electrolyte interfaces. A key structural
motif of these interfaces consists in 'paired' (inorganic)anion/(organic)cation layers that can have an enormous stability even during an ongoing charge transfer reaction. In this contribution we present and discuss a selected case study on the co-adsorption of halide anions and cationic
organic molecules that exhibit a pronounced redox activity. It will be demonstrated that their phase behavior at the interface crucially depends on both their particular redox-state and the surface concentration of the halide counter ions. The subtle balance between adsorbate–adsorbate
and adsorbate–substrate interaction of the poly-cationic organic layer can be carefully controlled by potential dependent anion adsorption and desorption processes through the organic layer. This process can be followed by in situ high-resolution scanning tunnelling microscopy,
while additional information about the structural and chemical state of the respective phase is obtained from in situ X-ray diffraction and ex situ photoelectron spectroscopy.
Cyclic voltammetry of the four cationic Ni sandwich com-characterized analytically and by an X-ray structure deterplexes [Ni(C5R5)(C4R$)]+ (2: R = H, R = Ph; 3 R = H, mination as the dimer 6 of 3, linked through cyclobutenyl R' = Me; 4 R = Me, R = Ph; 5: R = R = Me) shows re-rings, the first example for a dimerization of an electron-rich versible one-electron reductions for the phenyl derivatives 2 sandwich complex at a substituted C atom. EPR spectra of the and 4 and a peak pattern characteristic of reductive dimerineutral complexes 2 and 4 are compared to those of (1,5-cyzation/oxidative monomerization for the methyl derivatives 3 clooctadiene)(cyclopentadienyl)nickel (7) and are interpreted and 5. The product of the reduction of 3 was isolated and in terms of a substantial static Jahn-Teller distortion, Unter den potentiellen ElektroneniiberschuB-Sandwich-Komplexen verdient das System NiCp(CBD) (Cp = q5-C5R5, CBD = q4-C4R4) besonderes Interesse. In den letzten Jahren sind eine Reihe von metallorganischen Ni(1)-Komplexen der Konstitution NiCpL, rnit L2 = Diolefin'), Bi-pyridin3t4) und Diphosphan4) bekannt geworden, deren Existenz die besondere Fahigkeit des Nickels zur Stabilisierung eines radikalischen Grundzustandes belegt. Daher sollte Nickel(1) am ehesten in der Lage sein, als Zentralmetall auch fiir einen paramagnetischen Cyclobutadien-Komplex zu fungieren.Als Ausgangsverbindungen fur die Erzeugung, eventuell kurzlebiger, neutraler 19-Elektronen-Komplexe NiCp(CBD) bieten sich die betreffenden Kationen an, deren elektrochemische Reduktion Hinweise auf die Existenz und Lebensdauer der Neutralverbindung liefert.AufschluD iiber die Elektronenverteilung im Neutralkomplex kann uber die ESR-Spektren der paramagnetischen Cyclobutadien-Komplexe, insbesondere im Vergleich mit denen der neutralen Diolefinkomplexe NiCp(diolefin), von denen wir das Cyclooctadienderivat in Substanz isoliert haben, erhalten werden.
Ergebnisse S y nt hesenAls Ni(CBD)-Bausteine kommen die Halogeno-Komplexe fNi(C4Ph4)Br2Iz5) und [Ni(C4Me4)Cl2Iz6) in Betracht. Die Cyclopentadienylierung gelingt in beiden Fallen durch Umsetzung mit FeCp(C0)'Br bzw. [FeCp(C0)2]2 in siedendem Toluol" nach G1. (1). Fur die Einfiihrung eines Cp*-Liganden (Cp* = q5-C5Me5) in 1 a kann Cp*Li dienen. Mit der Methylverbindung 1 b trat die gewiinschte Reaktion nicht ein. Sie lieD sich schlieDlich mit SnCp*Me3 oder Cp*Tl cyclopentadienylieren. Es wurden so die im Cp-und im CBD-Ring verschieden substituierten Derivate [2 -5]X erhalten.
Laser beam welding generally does without the use of filler metal, in contrast to conventional welding processes. The use of filler metal in laser beam welding or in the combined GMA (gas‐metal‐arc) ‐ laser beam ‐ hybrid welding process widens the field of application for laser beam welding. The main advantages worthy of mention include, primarily, a greater weld gap bridging ability and a metallurgical influence on the weld metal.
Based on the current state of knowledge, this article gives a few examples of different materials and material combinations the limited weldability of which is broadened when filler metal is used with laser beam welding. Listed as examples are low‐alloy steels with partly elevated carbon contents, duplex steels, and the material combinations of steel/cast iron and austenite‐ferrite joints.
Besides laser beam welding with filler metal wire, examples of the combined GMA‐laser hybrid welding process are also described.
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