Transfer number, oxygen ions

Electrical Conduction by Proton Jumps. As mentioned in Sec. 24, a hydroxyl ion may be regarded as a doubly charged oxygen ion 0 , containing a proton inside the electronic cloud of the ion, which has the same number of electrons as a fluoride ion. The radius of the hydroxyl ion cannot be very different from that of the fluoride ion. But it will be seen from Table 2 that the mobility of the hydroxyl ion is about four times as great. This arises from the fact that a large part of the mobility is undoubtedly due to proton transfers.1 Consider a water molecule in contact with a hydroxyl ion. If a proton jumps from the molecule to the ion,... 

It has been known for many years that the mitochondrion shows a respiration-linked transport of a number of ions. Of these, calcium has attracted the most attention since it depends on a specific transport system with high-affinity binding sites. The uptake of calcium usually also involves a permeant anion, but in the absence of this, protons are ejected as the electron transfer system operates. The result is either the accumulation of calcium salts in the mitochondrial matrix or an alkalinization of the interior of the mitochondrion. The transfer of calcium inwards stimulates oxygen utilization but provides an alternative to the oxidative phosphorylation of ADP618 ... 

Equation (15.5) shows that for very high and very low A>2(/ o2) the transference number of the ions vanishes. From Eqn. (15.4), we read that ( E/dp oJ is zero if / (= 1 - /<.]) vanishes. This means that stabilized zirconia cannot be uied as a solid electrolyte in the ranges of oxygen potential where po>P and Pq2galvanic cells or in fuel cells. For p >Pot>P < the oxide is said to be in its electrolytic domain (Fig. 15-12). 

Sensor. The control of the exhaust composition was essential to maintain the air-to-fuel ratio close to stoichiometric for simultaneous conversion of all three pollutants. This control came about with the invention of the 02 sensor.21,22 The sensor head of this device was installed in the exhaust immediately at the inlet to the catalyst and was able to measure the 02 content instantly and precisely. It generates a voltage consistent with the Nemst equation in which the partial pressure of 02 (P02)exhaust in the exhaust develops a voltage (E) relative to a reference. The exhaust electrode was Pt deposited on a solid oxygen ion conductor of yttrium-stabilized zirconia (Zr02). The reference electrode, also Pt, was deposited on the opposite side of the electrolyte but was physically mounted outside the exhaust and sensed the partial pressure (P02)ref in the atmosphere. E0 is the standard state or thermodynamic voltage. R is the universal gas constant, T the absolute temperature, n the number of electrons transferred in the process, and F the Faraday constant. 

An alternative electrolyte material, lanthanum-doped barium indium oxide, (Ba,La)In205+3, has been proposed. This new material has been shown to have an ionic transference number of 1.0 with an oxygen ion conductivity better than that of YSZ. 

Conductivity The materials must have an ionic transference number close to unity i.e., the electronic conductivity in the electrolyte must be sufficiently low in order to minimize internal shorting and provide high energy conversion efficiency. The electrolyte materials should also possess high oxygen ion conductivity to minimize the ohmic losses in the cell. 

The luminescence of centres like VO "", WO , WOg has been treated in detail in Chap. I of this volume. These centres consist of a central highly-charged transition metal ion without d electrons and a number of surrounding oxygen ions (usually 4 or 6 in a tetrahedral or octahedral arrangement, respectively). The optical transitions involved are of the charge-transfer type and usually involve considerable lattice relaxation. 

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