Organic liquids cathodic process

With regard to the cathodic processes, it can be observed that any liquid medium, even organics, able to solvate the metal ions, may give rise to corrosion in the presence of any suitable cathodic process. The cathodic processes in inorganic environments may be numerous, not only the oxygen reduction or the hydrogen evolution, for example, the reduction of the nitrates to ammonia, that of the sulfates to sulfides, and that of the ferric to ferrous salts. 

There have been severe criticisms about the extended use of chlorine gas in industry, owing to concern primarily derived from its ability to form toxic chlorinated organic compounds. In order to avoid its co-production during the electrolytic production of sodium hydroxide, a process has been developed in which a sodium carbonate (soda ash) solution is used as the anolyte in an electrochemical reactor divided by an ion-exchange membrane. Hydrogen gas is produced at the cathode and sent to a gas diffusion anode. Assuming no by-products in the liquid phase and only one by-product in the gas phase ... 

If [BMIMJPFg ionic liquid is saturated with GeCLj (Figure 6.2), two main reduction processes (Pi and P2) are observed in the cathodic regime [42], The first reduction peak, with a minimum at +500 mV vs. Ge (Pi) is attributed to the reduction of Ge(IV) to Ge(II). At potentials below 0 mV (P2) the bulk deposition of Ge from Ge(II) sets in, as can be seen with the naked eye. The rising cathodic current at about —1000 mV vs. Ge is attributed to the irreversible reduction of the organic cation. If only Pi is passed, an oxidation process is not observed. If Ge deposition is performed an oxidation peak at 1000 mV is observed, which means that this peak must be correlated to Ge electrooxidation. A series of oxidation peaks above +1500 mV is also observed if the electrode potential is cycled between +1000 and... 

The liquid itself exhibits on Au(lll) an electrochemical window slightly more than 5 V (Figure 6.8). At the cathodic limit a series of peaks (C1-C3) is observed prior to the irreversible reduction of organic cation at —3200 mV vs. Fc/Fc+. At the anodic limit at +2000 mV vs. Fc/Fc+ gold oxidation sets in. The oxidation processes A3 and A4 are only observed if the reduction processes C3 and C4 have been passed. For the peaks Ci and C2 the respective oxidation processes are missing. It was shown that the peaks Q to C3 are correlated to the irreversible breakdown of the Tf2N ion [47, 48],... 

The cathodic reaction uses electrons, protons, and oxygen and produces liquid water which at the operation temperature partially evaporates. Furthermore, liquid water may diffuse through the membrane. So, here again, we have the situation that products and educts of a reaction are available in different phases, and we have to organize a counter flow process to support the reaction. 

It can be seen from Figure 21.2.11 that the [C4-mim] cation has a cathodic limit of approximately -2 V versus SCE and that this value is essentially the same for all of the [Cn-mim] cations. Given that the deposition potentials for many metals will fall positive of this potential, it becomes possible to use ionic liquids as electrolytes for metal plating and other similar processes. The broad electrochemical windows (in some cases, over 4 V) indicate that a variety of organic and inorganic electrochemical oxidations and reduction should be possible in ionic liquids. 

Electrodeposition of nanostructures by cathodic reduction of a metal salt at a suitable substrate represents the most important alternative synthetic procedure. Different methods have been employed for the deposition of metals, particularly of noble metals [194]. The electrodeposition may occur from different media although most of the studies deal with aqueous solutions, organic solvents and ionic liquids have also been employed [195]. An extensive literature dealing with electrodeposition of metals has been published due to the importance of such processes in industrial applications, e.g., in corrosion protection and in enhancement of mechanical and aesthetic properties [75, 194, 196-198]. 

The liquid metal Galinstan (composed of Ga, In, and Sn in approximate percentages of 68%, 21% and 10%, respectively) is reported to have % = 3—4 x lO S cm at room temperature, and a work function around 4.1. 4 eV, which make it a good cathode material for injecting electrodes into organic semiconductors. For these reasons, and for its liquid phase at room temperature, it may be an excellent choice for use in electrospinning processes and in combination with other techniques for the production of self-contacted, electrically excitable polymer nanostructures. 

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