Low-potential electrode

MERCURY (LOW-POTENTIAL ELECTRODE > SILVER LAYER (HIGH—POTENTIAL ELECTROOE) GLASS CAPILLARY GUISS TUBE... 

Accurate sample thickness determination of these thin foam disks is difficult. A guarded measuring cell with two low-potential electrodes (one disk electrode for the sample and one ring electrode for the sample thickness determination) was... 

The weight of the low-potential electrode slightly impressed the thin foam samples. Hence, capacity C2 was measured before and after the sample capacity (Cl) and conductance (Gl) measurement. The average sample thickness during the Cl/Gl determination was calculated using both C2 capacity values. These measurements were performed at 22"C 1°C and a relative humidity of 50%. The results of these measurements are collected in the Tables 5.3 and 5.4. 

Sample cells (Figure 5.16) were constructed upon the coated panels by glueing the polished end of glass tubes (internal diameter about 50 mm.) onto the coated surface with epoxy cement. The sample cells were stored at 22 2°C and a relative humidity of 55 + 5 per cent. The steel panel served as high potential electrode (H), and a mercury electrode, connected by a platinum wire, as low potential electrode (L). Guarding was achieved by using a bell-shaped brass cover which also supports the connector of the low potential electrode. 

The Ki-value determinations were performed on coils with a diameter of about 0.2 m., made of cable samples with a length of about 10 m. Such a coil is immersed in an (electrically insulated) water-bath filled with tapwater and kept at the specified temperature. The electrical resistance is then measured between the copper wire of the cable (high potential electrode) and the tapwater (low potential electrode). The Ki-value is calculated according to [29] ... 

An example of a PVC orientation depolarisation effect, measured with a combined TMA/TSD system is given in chapter 6. These orientation depolarisation effects were measured on small (i.e. 8 mm.) diameter, samples. Such samples proved to be too small, however, to detect the space charge depolarisation effects in non-polar SSBR rubbers. These non-vulcanised rubber samples were pressed, therefore, at 140°C between two (l mm thick) brass disks with a diameter of respectively 110 mm (high potential electrode) and 80 mm (low potential electrode) to a sample thickness of about 0.2 mm. A ring (inner/outer diameter 75/85 mm) of 50 micron thick Vespel foil avoided shortcircuiting between the two brass disks. 

An extension of hybrid redox flow batteries is the double hybrid soluble lead-acid flow batteries (SLFBs) where deposition and dissolution of redox active compounds are involved in both high potential and low potential electrode reactions. Fletcher et al. explored the concept of SLFBs in 2004 [112], and have reported their systematic study in a series of papers [113-120]. The electrode reactions of a SLFB are ... 

Whatever the model we assume, the experimental fact is that highly acidic fillers enhance stability and transport properties of the interfaces with low potential electrodes as presented in Fig. 2.8. 

One criterion for the anode material is that the chemical potential of lithium in the anode host should be close to that of lithium metal. Carbonaceous materials are therefore good candidates for replacing metallic lithium because of their low cost, low potential versus lithium, and wonderful cycling performance. Practical cells with LiCoOj and carbon electrodes are now commercially available. Finding the best carbon for the anode material in the lithium-ion battery remains an active research topic. 

In general, the baser the metal, the lower (more negative) the electrical potential at the anode and the higher the potential rate of corrosion. Carbon steel and low-alloy steels (which are widely used in boiler plants) have a relatively low potential with respect to the standard hydrogen electrode and can therefore be expected to corrode readily unless active prevention measures are taken. Copper and brasses have a relatively higher potential. 

Structural effect was confirmed by in situ infrared spectroscopy which showed a high coverage of adsorbed CO on a R( 110) plane conversely, on the other single-crystal planes, a distribution of different species is clearly visible. Further, strong lateral interactions between the different adsorbed species on Pt(lOO) lead to very low activity of this electrode at low potentials. ... 

On the other hand, the Pt(lOO) electrode showed almost no currents in the positivegoing scan, a clear indication that the surface is completely blocked by the poisoning intermediate, which is accumulated on the surface at low potentials. Once the poison is oxidized, above 0.7 V (vs. RHE), currents in the negative-going scan are almost one order of magnimde higher than those recorded for Pt(lll) [Clavilier et al., 1981]. This indicates that both paths of the reaction mechanism are much faster for the Pt(lOO) electrode. 

The qualitative voltammetric behavior of methanol oxidation on Pt is very similar to that of formic acid. The voltammetry for the oxidation of methanol on Pt single crystals shows a clear hysteresis between the positive- and negative-going scans due to the accumulation of the poisoning intermediate at low potentials and its oxidation above 0.7 V (vs. RHE) [Lamy et al., 1982]. Additionally, the reaction is also very sensitive to the surface stmcture. The order in the activity of the different low index planes of Pt follows the same order than that observed for formic acid. Thus, the Pt(l 11) electrode has the lowest catalytic activity and the smallest hysteresis, indicating that both paths of the reaction are slow, whereas the Pt( 100) electrode displays a much higher catalytic activity and a fast poisoning reaction. As before, the activity of the Pt(l 10) electrode depends on the pretreatment of the surface (Fig. 6.17). 

The following are now expected first, in the CO oxidation electrode potential range on Pt/Ru surfaces (i.e., at low potentials), entrapped oxygen should be found second, the entrapped (subsurface) oxygen concentration between the Ru layers should increase with increasing multilayer character (and coverage) of the Ru deposit on Pt. Research focusing on these two issues is planned. 

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