Thin electrolyte layers

In steady-state measurements at current densities such as to cause surface-concentration changes, the measuring time should be longer than the time needed to set up steady concentration gradients. Microelectrodes or cells with strong convection of the electrolyte are used to accelerate these processes. In 1937, B. V. Ershler used for this purpose a thin-layer electrode, a smooth platinum electrode in a narrow cell, contacting a thin electrolyte layer. 

In the early work of Bewick and Robinson (1975), a simple monochromator system was used. This is called a dispersive spectrometer. In the experiment the electrode potential was modulated between two potentials, one where the adsorbed species was present and the other where it was absent. Because of the thin electrolyte layer, the modulation frequency is limited to a few hertz. This technique is referred to as electrochemically modulated infrared reflectance spectroscopy (EMIRS). The main problem with this technique is that data acquisition time is long. So it is possible for changes to occur on the electrode surface. 

Because of the close distance between electrode and window the concentration of methanol in the thin electrolyte layer diminishes at positive potentials and can only slowly be supplied by diffusion. In order to have measurable quantities of formic acid (or methyl formate) one has to work with methanol concentrations in the order of 1 M or more. 

Figure 2.46 Schematic diagram showing the angle of incidence at the electrode for (a) an angle of incidence of 65° at a plate window (W), and (b) the incoming ray incident normal to the face of a prismatic window (P), having a bevel of 65 , assuming RM Vn)( = 1.33, Venl = 0, nwind(> = 1.4, kwiBdow = 0, ni([ = 1, and k, = 0. TL = thin electrolyte layer, E = electrode,...

This section and the next are dedicated to the basics of the silicon-electrolyte contact with focus on the electrolyte side of the junction and the electrochemical reactions accompanying charge transfer. The current across a semiconductor-electrolyte junction may be limited by the mass transport in the electrolyte, by the kinetics of the chemical reaction at the interface, or by the charge supply from the electrode. The mass transport in the bulk of the electrolyte again depends on convection as well as diffusion. In a thin electrolyte layer of about a micrometer close to the electrode surface, diffusion becomes dominant The stoichiometry of the basic reactions at the silicon electrode will be presented first, followed by a detailed discussion of the reaction pathways as shown in Figs. 4.1-4.4. 

In these experiments cells are designed that have a thin electrolyte layer over the working electrode covered by a window that is transparent to the incident radiation. Refraction of the beam by the window has to be taken into account in the calculations. 

An additional advantage of the proposed solar energy devices would be that they could be built of cheap materials. They could, for example, be made of carbon, a graphite layer anode and a sheet of amorphous carbon as a cathode separated by a thin electrolyte layer with bromide/bromine as a carrier system. 

As for the sealed lead-acid, a thin electrolyte layer is used to help oxygen transfer. 

Then, O2 migrates to the negative through the thin electrolyte layer and gives rise to the reaction ... 

Thus, the transport of hydrated ions and chemical debonding processes can be studied by means of the SKP. Fig. 31.6 shows the potential distribution measured with the SKP when a thin electrolyte layer enters the interface between an adhesive and an iron surface covered by a thin (about 6 nm) nonconducting SiOx layer precipitated by a plasma-polymerization process [51, 52]. The SiO layer inhibits the electron-transfer reaction. Consequently, no corrosive degradation of the interface takes place (see Section 31.3.2.1). However, as the adhesion of the epoxy adhesive to the siUca-Uke layer is weak, the polymer is replaced by... 

The oxygen diffusion coefficient, which was determined by the method of isotope exchange for thin electrolyte layers [6],... 

Metals exposed to humid atmosphere corrode by an electrochemical mechanism due to the formation of a thin electrolyte layer on the metal surface (Chapter 3.1, this volume). This type of corrosion can be controlled by Vapor-phase Corrosion Inhibitors (VCIs), that is, volatile inhibiting substances that allow vapor-phase transport to the corroding surface (examples are amines, benzoates, imidazoles, or triazoles [3]). The vapor pressure should be sufficiently high to ensure a protective surface concentration of the inhibitor, but low enough to prevent premature depletion of... 

Y. Tsutsumi, A. Nishikata, T. Tsuru, Initial stage of pitting corrosion of type 304 stainless steel under thin electrolyte layers containing chloride ions corrosion, passivation, and anodic films, J. Electrochem. Soc. 152 (2005) B358-B363. 

M. Stratmann, H. Streckel, On the atmospheric corrosion of metals which are covered with thin electrolyte layers—II. Experimental results, Corros. Sci. 30 (1990) 697—714. 

G. A. El-Mahdy, Advanced laboratory study on the atmospheric corrosion of zinc under thin electrolyte layers. Corrosion 59 (2003) 505—510. 

The operation temperature of portable SOFC may lie weU below 600 °C and can be reduced to 350 °C. These low temperatures can be achieved by extremely thin electrolyte layers being produced with MEMS techniques. Thin electrolyte layers have a low diffusion resistivity for oxygen anions and thus a sufficiently low ohmic resistivity at low temperature. 

Electrochemical reactions can only take place at those platinum particles where ion conducting phase, catalyst and electron conducting phase simultaneously meet the reactants [53]. The reaction site can be either at a three phase boundary or more likely at a catalyst particle only covered by a very thin electrolyte layer. Figure 14.10 shows a schematic view of the membrane electrode assembly. 

The setup for external reflection absorption spectroscopy is shown in Fig. 1. A PPy-covered platinum disc electrode is pressed against a ZnSe window, yielding a distance of some m between the electrode and the window. The electrochemical current of the oxidation process has to pass the thin electrolyte layer. Since only parallel-polarized light interacts with substances near a reflecting metal surface, the nt light was polarized in this way. The IR beam permeates the window, the electrolyte and the polymer and is reflected at the Pt surface. Only this part of the radiation (a in Fig. 1) contains information on the polymer absorption. Reflections at the window and the polymer surface b, c and d in Mg. 1), which also reach the detector, can lead to disturbing spectral features and have to be eliminated or corrected. ... 

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