Reactivity electrochemical current efficiencies

The work on the electrochemical generation of a solution of ceric sulphate from slurry of cerous sulphate in 1-2 M sulphuric acid was abandoned by BCR due to difficulties encountered in handling slurried reactants. A 6kW pilot reactor operated at 50 °C using a Ti plate anode and a tungsten wire cathode (electrolyte velocity about 2ms 1) produced 0.5 M Ce(S04)2 on the anode with a current efficiency of 60%. The usefulness of Ce(IV) has been limited by the counter anions [131,132], Problems include instability to oxidation, reactivity with organic substrates and low solubility. Grace found that use of cerium salts of methane sulfonate avoids the above problems. Walsh has summarized the process history, Scheme 6 [133],... 

Then when CoTTP-py-NHCO-GC modified electrode is obtained, the catalytic activity towards the electrochemical reduction of CO2 showed a current efficiency of 92% for CO production and also an overall turnover number of 10 at -1.1 V vs. SCE. As mentioned before the CoTTP in CoTTP-py-NHCO-GC electrode is in the form of a five coordinate complex with a pyridine ligand, with a vacant site at the trans position to pyridine. It is expected that CO2 reduction occurs at vacant site to which pyridine gives specific reactivity through the called trans effect. The axial pyridine ligand could favor an electron transfer from Co of the complex to CO2, since it increases the electron transfer ability of Co, as in the case of an O2 carrier, and facilitates the reduction of C02 . ... 

The only physical difference is that here the current, I, is not directly measurable and thus the dimensionless current density, J, is not directly computable. This difficulty can, however, be overcome if the ratio of the reactivities, A, of normally adsorbed and backspillover oxygen is known (e.g. from electrochemical promotion experiments, where A, as already noted, also expresses the Faradaic efficiency). Thus in this case upon combining the definition of A with equation (11.23) one obtains the following expression for J ... 

Other electrochemical ways have been attempted to generate an activated zinc surface from massive zinc (rod or plate). Two types of activation have been developed. In the first one, a low current density is applied on the massive zinc, which is used as the anode. The electroscoring of the zinc surface makes it reactive towards organic halides that are easily reducible. These reactions are catalytic in electricity. This electroscoring, which is all the more efficient as the applied current density is low, is equivalent to an acidic treatment of the surface. 

A fifth reason for using microfluidics in electrochemistry would be the possibility to combine flow chemistry with an ultrafast mixer, which allows the generation and subsequent use of short-lived reactive ions or radicals, for example, in a "cation flow" process (Suga et al., 2001 Yoshida, 2008). Finally, a sixth reason for performing electrochemistry in a microfluidic system may be the desire to efficiently remove reaction heat (or joule heat due to high currents in combination with a high ohmic resistance) in fast electrochemical reactions (Yoshida, 2008). 

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