Nemst mass

Yttria-stabilized zirconia (YSZ), e.g., the Nemst mass (ZrC>2)o.84( 203)o.o8 = Zro.84Eo.i6 O1.92, is an example for a complete cation lattice and an incomplete anion lattice ... 

Mobius HH (1965) The Nemst mass, its history and present importance (in German). Naturwissen 52 529-536... 

Mobius H-H (1965) The Nemst mass—its history and today s importance. Natiffwissensch 52 529-536, Published in German Die Nemst-Masse, ihre Geschichte und heutige Bedeutung... 

The SOFC was derived from the Nemst glower, originally intended as a commercial light source to replace caibon filament lamps at the end of the last centniy. This device made nse of the Nemst mass composed of yttria-stabilized zirconia (YSZ), a predominantly ionic... 

The expression for the mass-transport-limiting current density may be employed together with the Nemst equation to deduce the complete current-potential response in a solution containing only oxidized or reduced species... 

The chronoamperometric technique illustrates the principle that analytically useful current responses depend critically on the efficiency of analyte mass transport within the solution. The analyte mass transport in turn depends on the efficiency with which an appHed voltage can maintain the surface concentrations of oxidized and reduced species at values specified by the Nemst equation. It is generally the case in chronoamperometry that the bulk concentration of one of the species is zero whereas the surface concentration of the other species is forced to zero by the appHed potential, but this is not always so. 

Clausius-Clapeyron, 230,303-305 Gibbs-Helmholtz, 459,461 Henderson-Hasselbalch, 79-80 mass relation, 62-63 Nemst, 493-494 net ionic, 79-80 nonmetals, 575q nuclear, 513,530-531q Planck s, 135 redox, balancing, 90-92 Schrodinger, 140 thermochemical, 204... 

The flux ( J ) is a common measure of the rate of mass transport at a fixed point. It is defined as the number of molecules penetrating a unit area of an imaginary plane in a unit of time, and has the units of mol cm 2 s-1. The flux to the electrode is described mathematically by a differential equation, known as the Nemst-Planck equation, given here for one dimension ... 

Well-defined hydrodynamic conditions, with high rate of mass transport, are essential for successful use of electrochemical detectors. Based on the Nemst approximate approach, the thickness of the diffusion layer (<5) is empirically related to the solution flow rate (U) via... 

The micro structured platelets, hold in a non-conducting housing, were realized by etching of metal foils and laser cutting techniques [69]. Owing to the small Nemst diffusion layer thickness, fast mass transfer between the electrodes is achievable. The electrode surface area normalized by cell volume amounts to 40 000 m m". This value clearly exceeds the specific surface areas of conventional mono- and bipolar cells of 10-100 m m. ... 

The original and simplest form of the diffusion layer theory was developed by Nemst [105] and Brunner [106], who assumed that the mass flux is given by Fick s first law of diffusion. In that case,... 

For a triphasic reaction to work, reactants from a solid phase and two immiscible liquid phases must come together. The rates of reactions conducted under triphasic conditions are therefore very sensitive to mass transport effects. Fast mixing reduces the thickness of the thin, slow moving liquid layer at the surface of the solid (known as the quiet film or Nemst layer), so there is little difference in the concentration between the bulk liquid and the catalyst surface. When the intrinsic reaction rate is so high (or diffusion so slow) that the reaction is mass transport limited, the reaction will occur only at the catalyst surface, and the rate of diffusion into the polymeric matrix becomes irrelevant. Figure 5.17 shows schematic representations of the effect of mixing on the substrate concentration. 

When a biocatalyst is immobilized on or within a solid matrix, mass transfer effects may exist because the substrate must diffuse from the bulk solution to the immobilized biocatalyst. If the biocatalyst is attached to non-porous supports there are only external mass transfer effects on the catalytically active outer surface in the reaction solution, the supports are surrounded by a stagnant film and substrate and product are transported across this Nemst layer by diffusion. The driving force for this diffusion is the concentration difference between the surface and the bulk concentration of substrate and product. 

The difference between and in Figure 6 is a measure of the total concentration of the first redox couple. 2 is a measure of the total concentration of the second redox couple. The equilibrium potential provides the two ratios of oxidized to reduced species according to the Nemst equation. From all this information the concentrations of both oxidized and reduced species can be determined. In this case the EP s of the two species are so far apart that their voltammograms are well resolved. The second redox couple must be wholly in its oxidized form whereas the first must be in a ratio equal to the ratio of the absolute values of its limiting currents, corrected by the mass-transfer coefficients. 

For an electrode reaction to be considered reversible, it is necessary to compare the rate of the charge transfer process and the rate of the mass transport of electroactive species. When the mass transport rate is slower than the charge transfer one, the electrode reaction is controlled by the transport rate and can be considered as electrochemically reversible in that the surface concentration fulfills the Nemst equation when a given potential is applied to the electrode. In Electrochemistry, knowledge of the behavior of reversible electrode processes is very important, since these can be used as a benchmark for more complex systems (see Chap. 5 in [1] and Sect. 1.8.4 for a detailed discussion). 

In this section, a non-reversible electrode reaction will be addressed. An exact definition of a slow charge transfer process is not possible because the charge transfer reaction can be reversible, quasi-reversible, or irreversible depending on the duration of the experiment and the mass transport rate. So, an electrode reaction can be slow or non-reversible when the mass transport rate has a value such that the measured current is lower than that corresponding to a reversible process because the rate of depletion of the surface species at the electrode surface is less than the diffusion rate at which it reaches the surface. Under these conditions, the potential values that reduce the O species and oxidize the R species become more negative and more positive, respectively, than those predicted by Nemst equation. 

Under discharge, the oxidation of MH is associated with the reduction of NiOOH into Ni(OH)2 in the positive active mass. When the external circuit is open (no current), the active mass (Reaction 1.1) confers to the negative current collector, a potential versus the standard hydrogen electrode (SHE) according to the Nemst law ... 

First, the different components of the bulk solution must be brought up to the electrode surface by the processes summarized under the heading mass transfer. Convection (movement of the solution relative to the electrode) takes molecules and ions to the boundary of the Nemst layer (Section 2), through which diffusion takes them up to the electrode surface. Diffusion occurs due to the... 

A Nemst glower is an obsolete infrared source that consists of a ceramic bar (90 mass% Zr02 7% Er203 7% Y203) operated between 1000°C and 2000°C. 

The ion transfer across the liquid/liquid interface is fast in comparison with the mass transfer at least at the planar interface in conventional timescale of longer than millisecond the ion transfer can be treated as an electrochemically reversible process [24,29]. The adsorption also seems to be fast under the same condition [14]. Thus it is a good approximation to assume the Nemst equation for the surface concentrations cp(x = 0) and — 0) ... 

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