Anodes formation

The formation of colloidal sulfur occurring in the aqueous, either alkaline or acidic, solutions comprises a serious drawback for the deposits quality. Saloniemi et al. [206] attempted to circumvent this problem and to avoid also the use of a lead substrate needed in the case of anodic formation, by devising a cyclic electrochemical technique including alternate cathodic and anodic reactions. Their method was based on fast cycling of the substrate (TO/glass) potential in an alkaline (pH 8.5) solution of sodium sulfide, Pb(II), and EDTA, between two values with a symmetric triangle wave shape. At cathodic potentials, Pb(EDTA)2 reduced to Pb, and at anodic potentials Pb reoxidized and reacted with sulfide instead of EDTA or hydroxide ions. Films electrodeposited in the optimized potential region were stoichiometric and with a random polycrystalline RS structure. The authors noticed that cyclic deposition also occurs from an acidic solution, but the problem of colloidal sulfur formation remains. 

In their pioneering work on the formation of photoelectrochemically active metal sulfides by oxidation of the parent metal electrode. Miller and Heller [29] reported the anodic formation of polycrystalline Bi2S3 on a bismuth metal electrode in a sodium polysulfide cell, wherein this electrode was used in situ as photoanode. When a Bi metal electrode is anodized in aqueous sulfide solutions a surface film is formed by the reaction... 

MiUer B, Menezes S, Heller A (1978) Anodic formation of semiconductive sulfide films at cadmium and bismuth Rotating ring-disk electrode studies. 1 Electroanal Chem 94 85-97... 

Yeh LSR, Hudson PG, Damjanovic A (1982) Anodic formation of thin CdS films. I. Kinetics and mechanisms under galvanostatic and potentiodynamic conditions. J Appl Electrochem 12 153-162... 

Birss VI, Wright GA (1981) The kinetics of the anodic formation and reduction of phase silver sulfide films on silver in aqueous sulfide solutions. Electrochim Acta 26 1809-1817 Petrov GV, Belen ku AM (2005) Interactions in the silver selenide-water system. Russ J Appl Chem 78 53-56... 

The current-producing steps (those producing electrons) are the ionization of adsorbed hydrogen atoms and the anodic formation of new species from water molecules ... 

Under certain conditions (e.g., during times at open circuit when the anodic formation of is not possible), the are transformed to =COj,, which are... 

The applicability of this technique is based on four assumptions (1) the number of coulombs per square centimeter used for the anodic formation of an oxygen layer (20H = Oads + H2O + 2e) and the oxygen evolution during the sweep are the... 

An interesting aspect of fluoride applications in electrochemistry is the beneficial effect that fluoride-containing electrolyte media have on the anodic formation of ozone. Oxidized forms of fluoride are known to result in the formation of persulfate and peroxide, but for the... 

Finally, the electroiodofluorination of alkynes and alkenes has been reported [179]. The process occurs with high regioselectivity and is based on the anodic formation of an iodonium ion in the presence of iodide and fluoride. 

Gambaretto and co-workers [172] showed that the ECF of benzoyl chloride occurred at voltages below those at which fluorine was evolved in the absence of the organic (using a blank solution of KF in HF of the same conductivity), and claimed this meant that fluorination may have occurred without anodic formation of fluorine atoms, i.e., by implication, it did occur via the discharge of the organic compound. 

Iodide is used as catalyst for the indirect anodic formation of the P—N bond to generate A-substituted dialkylphosphoramidates from phosphites (Eq. (57) Table 4, No. 36)... 

According to Fig. 7, Ru02 is certainly the catalyst of highest catalytic activity—but it is not stable in caustic solution and dissolves due to anodic formation of RuOi within several days. All mixed oxides containing Co irrespective of their composition show anodic overpotentials comparable to... 

Thus contrary to the naive understanding, Pt does not catalyze but prohibits the thermodynamically favored oxidation, allowing for homogenous dimerization of the Kolbe radicals and similar radicals due to blocking the anode by a layer of adsorption-stabilized species, whereas C anodes allow for physisorption of radicals with subsequent immediate anodic formation of carbenium cations, which constitutes a completely different reaction path. 

A comparable positive influence as experienced with anodic dimerization of olefins, styrene in particular, exerts carbon anodes on the anodic formation of trisarene sulfonium cations by anodic coupling of diarylsulfide radical cations to arenes (226-228). 

The applicability of this technique is based on four assumptions (1) the number of coulombs per square centimeter used for the anodic formation of an oxygen layer (20H=Oads + H20 + 2e) and the oxygen evolution during the sweep is the same in either the absence or presence of methanol (2) the same number of electrons per molecule, independent of the amount of the adsorbed methanol, is used up in the oxidation (3) the double-layer charging current is the same in the presence or absence of methanol and (4) the anodic sweep is sufficiently fast (here 800 V/s) such that oxidation of methanol, which diffuses from the bulk solution to the electrode during the sweep, is negligible (i.e., only the adsorbed methanol is oxidized). 

M. J. Schimmel and H. Wendt, Proc. Electrochem. Soc. 97-20, p. 16. Anodic formation of tenary semiconductors. 

The anodic formation of peroxodisulphate and peroxomonosulphate on Pt is a well-known process [(7.63) and (7.64) Oloman 1996]. 

Anodization — Formation of a film on an electrode by means of an anodic (oxidation) process. Electrooxidation of silver in a chloride-containing solution results in the formation of an AgCl-film because the solubility product of AgCl is rapidly surpassed upon oxidation of silver. The AgCl-coated silver is suitable for preparation of a Ag/AgCl -> reference electrode. Formation of an oxide layer on other metals (e.g., in case of aluminum) may result in improved surface properties (corrosion resistance, hardness, optical properties). 

Applications of this electrode material include (i) the anodic formation of hydroxyl radicals, (ii) the anodic formation of ozone and peroxo species, (iii) waste degradation in aqueous solution (hazardous and a range of organic wastes have been broken down without toxic intermediates), (iv) as a mechanically robust electrode for solid state electrochemistry or in the presence of power ultrasound, (v) as a dimensionally stable electrode, (vi) as a IR and Vis transparent electrode material, and (vii) as an inert substrate for electro-catalysts. 

According to the previous discussions, the above mentioned PEVD composite anode microstructure is largely based on PEVD s unique electro-crystallization behavior.Thus, PEVD has the capability of fabricating composite anodes to meet all the criteria for theoretically ideal anodes as illustrated in Figure 29. Furthermore, with regard to cost efficiency, PFVD is a single step process for composite anode formation. It can be conducted in situ to coat the pure metallic anodes, or even to repair damaged composite anodes for SOFCs. 

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