Alloy/electrolyte interface

Adsorption of various organic compounds (e.g., cyclohexanol, adamantanol-1, and camphor) has been studied at a renewed Sn + Pb alloy/electrolyte interface.820-824 The time variation of the surface composition depends on the solution composition, the nature and concentration of the surface-active substance, and on E. The " of cyclohexanol for just-renewed Sn + Pb alloys shifts toward more negative E with time, i.e., as the amount of Pb at the Sn + Pb alloy surface increases. 

Some basic aspects of alloy dissolution are best illustrated by the behavior of a liquid binary alloy A-B. This is due (1) to the absence of crystallization overvoltage and dissolution induced structural surface modifications [6] as well as (2) to the high diffusivity in the alloy phase that provides for the reactant supply at the alloy/electrolyte interface if one alloy component dissolves preferentially (at a higher rate than the other) (7). Provided that the standard electrode potential difference of the components, AE = E — El, is large AE > RT/F) and their charge transfer reactions are fast, one expects a schematic polarization curve as shown by Fig. 1(a). For Ea < E < Eb, only the less noble component. A, dissolves ( selective dissolution or deaUoying ), the partial anodic... 

Here, x is the distance from the (original) alloy/electrolyte interface, D is the interdiffusion coefficient in the alloy, t is the polarization time, and may be thought... 

Theoretical Aspects Every model of selective alloy dissolution must involve a transport mechanism by virtue of which the atoms of the less noble component reach the alloy/electrolyte interface and the atoms of the more noble component aggregate. For a binary alloy, the basic transport mechanisms are as follows ... 

Electrical double layer at soKd metal alloy-electrolyte interface have been studied, but one of the features of alloys is that... 

Enumerate aU of the metal atoms and electrolyte components in the alloy-electrolyte interface and store their dissolution (if appropriate) and diffusion rates along with potential exchange sites. 

It is now well established that in lithium batteries (including lithium-ion batteries) containing either liquid or polymer electrolytes, the anode is always covered by a passivating layer called the SEI. However, the chemical and electrochemical formation reactions and properties of this layer are as yet not well understood. In this section we discuss the electrode surface and SEI characterizations, film formation reactions (chemical and electrochemical), and other phenomena taking place at the lithium or lithium-alloy anode, and at the Li. C6 anode/electrolyte interface in both liquid and polymer-electrolyte batteries. We focus on the lithium anode but the theoretical considerations are common to all alkali-metal anodes. We address also the initial electrochemical formation steps of the SEI, the role of the solvated-electron rate constant in the selection of SEI-building materials (precursors), and the correlation between SEI properties and battery quality and performance. 

The electrical double-layer (edl) properties pose a fundamental problem for electrochemistry because the rate and mechanism of electrochemical reactions depend on the structure of the metal-electrolyte interface. The theoretical analysis of edl structures of the solid metal electrodes is more complicated in comparison with that of liquid metal and alloys. One of the reasons is the difference in the properties of the individual faces of the metal and the influence of various defects of the surface [1]. Electrical doublelayer properties of solid polycrystalline cadmium (pc-Cd) electrodes have been studied for several decades. The dependence of these properties on temperature and electrode roughness, and the adsorption of ions and organic molecules on Cd, which were studied in aqueous and organic solvents and described in many works, were reviewed by Trasatti and Lust [2]. 

For alloys the corrosion properties, as well as the composition of the passive layers, depend strongly on the chemical properties of the alloy components. For an alloy of chemically very different components, the noble metal tends to stay within the metal matrix, whereas the non-noble partner enters preferentially the oxide matrix or is dissolved more readily. The more-noble component enters the passive layer or is dissolved only if the potential is sufficiently positive. The more-noble component will be oxidized also later on a time scale if the potential is sufficiently positive. Besides thermodynamics also the kinetic properties of the system under study have a decisive influence on the various reactions. This involves the rate of transfer reactions at the metal/oxide and oxide/electrolyte interface, as well as the transfer of the cations and anions across the oxide matrix. 

Brattain and Garrett took a thin wafer of germanium and by alloying one side of it with indium formed a p-n junction with the p-side very much more heavily doped than the n-side, so that any current flow across the junction would be due to holes (5). The n-side of the junction was brought into contact with the electrolyte and current was then passed across the electrolyte interface under various potentials. Under these conditions the voltage which develops between the two ohmic contacts to the semiconductor is a measure of the minority-carrier density on the less-heavily-doped side of the junction. 

The formation of 2D Meads phases on a foreign substrate, S, in the underpotential range can be well described considering the substrate-electrolyte interface as an ideally polarizable electrode as shown in Section 8.2. In this case, only sorption processes of electrolyte constituents, but no Faradaic redox reactions or Me-S alloy formation processes are allowed to occur, The electrochemical double layer at the interface can be thermodynamically considered as a separate interphase [3.54, 3.212, 3.213]. This interphase comprises regions of the substrate and of the electrolyte with gradients of intensive system parameters such as chemical potentials of ions and electrons, electric potentials, etc., and contains all adsorbates and all surface energy. Furthermore, it is assumed that the chemical potential //Meads is a definite function of the Meads surface concentration, F, and the electrode potential, E, at constant temperature and pressure Meads (7", ). Such a model system can only be... 

Abnormal Infrared Effects of Nanometer-Scale Thin Film Material of Platinum Group Metals and Alloys at Electrode-Electrolyte Interfaces... 

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