Electronic transference numbers

Electronic conductivity of thin-film solid electrolytes. Besides having low electronic transference numbers, it is essential for thin films of the order of 1 jim that the magnitude of the electronic resistance is low in order to prevent self-discharge of the battery. For this reason, specific electronic resistances in the range of 1012-1014 Qcm are required for thin-film solid electrolytes. Often the color may be a valuable indication of the electronic conductivity. In this regard, solid electrolytes should preferably be transparent white [20]. 

The nanostructured Au and AuPt catalysts were found to exhibit electrocatalytic activity for ORR reaction. The cyclic voltammetric (CV) curves at Au/C catalyst reveal an oxidation-reduction wave of gold oxide at +200 mV in the alkaline (0.5 M KOH) electrolyte but little redox current in the acidic (0.5 M H2SO4) electrolyte. Under saturated with O2, the appearance of the cathodic wave is observed at -190 mV in the alkaline electrolyte and at +50 mV in the acidic electrolyte. This finding indicates that the Au catalyst is active toward O2 reduction in both electrolytes. From the Levich plots of the limiting current vs. rotating speed data, one can derive the electron transfer number (w). We obtained n = 3.1 for ORR in 0.5 M KOH electrolyte, and 2.9 for ORR in 0.5 M H2SO4 electrolyte. The intermittent n-value between 2 and 4 indicates that the electrocatalytic ORR at the Au/Ccatalyst likely involved mixed 2e and 4e reduction processes. 

On the basis of the combined weight of the above results, we believe that bifunctional electrocatalytic properties may be operative for both MOR and ORR on the AuPt bimetallic nanoparticle catalysts depending on the nature of the electrolyte. For ORR in acidic electrolyte, the approaching of both the reduction potential and the electron transfer number for the bimetallic catalyst with less than 25%Pt to those for pure Pt catalyst is indicative of a synergistic effect of Au and Pt in the catalyst. For MOR in alkaline electrol)he, the similarity of both the oxidation potential and the current density for the bimetallic catalyst with less than 25%Pt to those for pure Pt catalyst is suggestive of the operation of bifunctional mechanism. Such a bifunctional mechanism may involve the following reactions ... 

According to Peled s model, the existence of an SEI constitutes the foundation on which lithium ion chemistry could operate reversibly. Therefore, an ideal SEI should meet the following requirements (1) electron transference number 4 = 0 (otherwise, electron tunneling would occur and enable continuous electrolyte decomposition), (2) high ion conductivity so that lithium ions can readily migrate to intercalate into or deintercalate from graphene layers, (3) uniform morphology and chemical composition for ho-... 

All materials in the Lai- r ,Coi- Fe/)3-(5 (LSCF) family of materials have electronic transference numbers approaching unity. The electronic structure LSC and LSF has often been described in terms of partially delocalized O p—Co band states based on the tg and e levels of crystal-field theory. In... 

Zn UPD on Pt Underpotential deposition of zinc was observed on Pt(l 11) in alkaline solution as a sharp cyclic voltammetric (CV) peak, in contrast to the behavior on polycrystalline Pt, when several broad UPD peaks were observed [193]. The changes of the peak potential with concentration of Zn02 were equal to 60 mV/log [Zn02 ] and led to the apparent electron transfer number ria = 1. 

This value is discussed in terms of two-electron transfer when Zn + is reduced to free zinc on Pt(lll) surface with a true electron transfer number of = 2. Also, induced adsorption of OH ions takes place to give OHads in an oxidative process. 

We begin our discussion by characterizing the electrical conduction in solid electrolytes. These are solids with predominantly ionic transference, at least over a certain range of their component activities. This means that the electronic transference number, defined as... 

Equations (4.94) and (4.95) provide examples of the fundamental equations which describe the electronic conduction in ionic solids. Figure 4-2 shows the electronic transference number tel as a function of the chemical potential of component X. 

In the derivation, the hopping conduction of the oxygen vacancies inside the interconnector [33], the conservation of the charge neutrality condition in the mixed conduction of the oxygen vacancies and the holes, and the unity of the electronic transference number are assumed. It has been reported [34] that Dv is experimentally given by... 

D0 is the oxygen self-diffusion coefficient a(02) is the oxygen activity C(02> is the oxygen concentration tA is the electronic transference number... 

The overall permeation rate of a material is determined by both ambipolar conductivity in the bulk and interfacial exchange kinetics. For -> solid electrolytes where the electron - transference numbers are low (see -> electrolytic domain), the ambipolar diffusion and permeability are often limited by electronic transport. 

This is only an approximate representation, in which a is the transfer coefficient and na is the apparent electron number involved in the pseudo-elementary reaction. This na is different from the total electron transfer number of the reaction ( ). 

The current in a PEVD process reveals the kinetics of the PEVD cathode reactions which, in turn, indicates the PEVD product growth behavior. Since the electronic transference number in Na+-P -alumina is less than 10" and can be ignored under the current experimental conditions, it is reasonable to assume that the only current passing through the internal circuit of the PEVD system is the sodium ionic current. 

For the example considered, the overall electron-transfer number in Eq. (16) is n = 2. 

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