Voltametric measurements

FIG. 24-14 Dissolved-oxygen electrodes a) polarographic (impress breakdown voltage for oxygen measure current) (h) voltametric (measure electromotive force). 

A limit of ca. 1.8% of Ti incorporation into the framework of the S-1 silicalite has been calculated by titration using Raman spectroscopy [14] or using voltametric measurements... 

The electron transfer series W(R2fi ic)4° W(R2tfic)4 -> W(R2rfic)4 was detected by voltametric measurements (37), the half wave potentials are 0.24 and 0.36 V lower than the corresponding values of the molybdenum compounds. Both transfers obey the Taft relation with a low value of p, which points to a rather small contribution of the ligand orbitals into the redox orbitals. 

The electron transfer Au(R2half-wave potentials of the quasi-reversible process depends on the substituent R according to the Taft relation, as was described for Mo, W and Mn 37). The value of p decreases in the series Au > Mn > Mo = W, which indicates that in this sequence the mixing of ligand orbitals into the redox orbital decreases. The dominant ligand character of the unpaired electron MO in Au(R2dtc)2 relative to those in copper and silver compounds is found from Extended Hiickel MO calculations, as will be discussed later on. 

In the titanosilicate system, cyclic voltametric measurements had indicated (Section III.D) that the electron density at the tripodal sites is higher than at the tetrapodal sites. Hence, by analogy with the chromium and manganese complexes, we may expect the tripodal sites to favor hydrogen abstraction and allylic CH oxidation, although electron transfer and epoxidation occur preferentially on the tetrapodal sites. 

Coatings of polyMPc prepared in situ form TCB on metal plates were investigated by cydic voltametric measurements Such electrodes show stable anodic and cathodic current densities comparable with a Pt electrode. Additionally, a large photo current was observed when using coatings of polyMPc on Ti-plates ... 

As well as chemical reactions, some physical measurements have been made. In particular, cyclic voltametric measurements have yielded reduction potentials for a series of arylxenon(II) tetrafluoro-borate salts that indicate that these are stronger oxidizers than the comparable aryliodonium salts (182). 

Cyclic voltametric measurements shown in Figure 14 indicate that only one surface layer is reduced. It is interesting to note that the reduction and reoxidation depends on the crystal faces.Capacity measurements proved that a new Helmholtz layer is formed after cathodic polarization " (see also Chapter 2). It could be further shown that the electronic level of the surface radical Ge is a surface state which is located between the conduction and valence bands, and which appears only as an intermediate state during the surface reduction process. Since the same surface state was detected again in the potential range in which H2 is finally formed, it has been postulated that the radical occurs as an intermediate state also in the mechanism of H2 evolution as given by ... 

From galvanostatic-charging curves with cyclic voltametric measurements, Breiter found that formic acid, adsorbed from 1 M solution, covers a platinum electrode essentially completely (6 1) between 0.1 and 0.8 V during an anodic potential sweep. However, on the cathodic sweep no formic acid species was... 

Tafel line with pH is (d log i/d pH) 0.5. The concentration dependence obtained by the change of height of the current peaks with concentration in cyclic voltametric measurements is given as (d log i/d log Cch3CH20hV ... 

All potentials determined from cyclic voltametric measurements... 

---