Electrochemical decomposition

Electrochemical detectors sense electroreducible and electrooxidizable compounds at low concentrations. Eor these detectors to work efficiently, the mobile phase (solvent) must be conductive and not subject to electrochemical decomposition. 

Whereas the electrochemical decomposition of propylene carbonate (PC) on graphite electrodes at potentials between 1 and 0.8 V vs. Li/Li was already reported in 1970 [140], it took about four years to find out that this reaction is accompanied by a partially reversible electrochemical intercalation of solvated lithium ions, Li (solv)y, into the graphite host [64], In general, the intercalation of Li (and other alkali-metal) ions from electrolytes with organic donor solvents into fairly crystalline graphitic carbons quite often yields solvated (ternary) lithiated graphites, Li r(solv)yC 1 (Fig. 8) [7,24,26,65,66,141-146],... 

M. Faraday, Experimental Researches in Electricity. Seventh Series. 11. On Electrochemical Decomposition, Philosophical Transactions of the Royal Society, 77-122 (1834). 

In practice, the decomposition potential for this overall reaction is found to be about 1.5 V this somewhat high value probably results from polarization and contact resistances. It could be seen that the electrochemical decomposition of alumina to deposit aluminum, using an inert anode, would require a theoretical cell voltage of 2.21 V as opposed to that of 1.18 V when carbon is used as the anode. Thus the participation of carbon in the cell reaction brings down the theoretically required cell voltage by almost 50%. 

This electrochemical decomposition requires about 1 V at the electrode surface. To drive the protons into the WO3 film, a proton-conducting electrolyte, typically... 

It was concluded from the results that RP-HPLC methods can be successfully employed for the study of the electrochemical decomposition of textile dyes [149],... 

The second approach is an adaptation of the voltammetry technique to the working environment of electrolytes in an operational electrochemical device. Therefore, neat electrolyte solutions are used and the working electrodes are made of active electrode materials that would be used in an actual electrochemical device. The stability limits thus determined should more reliably describe the actual electrochemical behavior of the investigated electrolytes in real life operations, because the possible extension or contraction of the stability window, due to either various passivation processes of the electrode surface by electrolyte components or electrochemical decomposition of these components catalyzed by the electrode surfaces, would have been... 

In many cases, the difference between these potentials—the window of operation without electrochemical decomposition of the solvent—is 3-4 V. In the aqueous case, it may in practice be as little as 1.5 V. On the other hand, even sodium can be electrodeposited from a solution of sodium acetate in ethanolamine. These advantages are countered by three factors that must be considered before a nonaqueous electrodeposition process is chosen as the best solution to co-deposition of H (Section 4.8.3). 

The thermodynamic breakdown energy for water is 1.23 eV. The electrochemical decomposition of water requires two electrons in consecutive steps. 

A profound thinker and accurate experimentalist and observer, he was the first to propound correct ideas as In the nature of electrical phenomena, not only in chemistry but in other fields His contributions lo chemistry include the basic laws of electrolysis, electrochemical decomposition (the basis of corrosion of metals) of hattery science, and electrometallurgy. 

Following his 1831 electromagnetic work, Faraday turned his attention to electrochemistry. The decomposition of chemical compounds was a standard test for the presence of electricity. In his extensive use of this test, he observed phenomena contradicting Davy s theory that electrochemical decomposition occurred at the metal pole. Faraday found that decomposition occurred in the substance itself and the poles did not need to be metal. All this led Faraday to develop a new language of electrochemistry. With a number of classical scholars, notably William Whewell, Faraday introduced terms such as electrolysis, electrolyte, electrode, anode, cathode, and ion (although he said there would be little need for this last term). 

Sonoyama N, Hara K, Sakata T. Reductive electrochemical decomposition of chloroform on metal electrodes. Chem Lett 1997 131-132. 

Sonoyama N, Sakata T. Electrochemical decomposition of CFC 12 using gas diffusion electrodes. Environ Sci Technol 1998 32 375-378. 

It is noteworthy that when the voltage is close to the electrochemical decomposition voltage there is an acceleration of the degradation phenomena, especially in the higher temperature domain. 

Photoelectrochemical Decomposition of HaS. The photo-electrochemical decomposition ofHjS on CdSe with solar light alone has an efficiency of only 1.8% (Kainthla, 1987). However, photoelectrocatalytic processes and the use of two-electrode photocells would be expected to greatly increase the efficiency of conversion.29... 

The coin has its reverse, however. The broadening of the potential window that is often bordered by the solvent electrochemical decomposition potentials (e.g. cathodic hydrogen evolution and anodic oxygen evolution from water) is due to an increase in reactions overvoltage. This may be caused by a diamond s lower electrochemical activity, as compared with the glassy carbon and like electrode materials. On the whole, this conclusion is corroborated by the kinetics studies on diamond electrodes... 

The theoretical voltage needed for electrochemical decomposition of chloride under the simultaneous formation of chlorate is calculated in the same way as has been used for hypochlorites. In a neutral solution (a0u- = 10 7) at a hydrogen pressure of pH, = 1 atm., the reduction potential at the cathode where reaction (XVII-10) occurs, will equal... 

Decomposition potential (voltage) — The onset voltage for electrochemical decomposition of the electrolytic solution or the electrodes. The decomposition can take place due to either oxidation or reduction, or both. The decomposition potentials define the electrochemical window of the system. Its value depends on the salt, solvent, electrode material, temperature, and the existence of materials that can catalyze decomposition reactions, such as Lewis acids. Exact decomposition voltages are hard to reproduce as the onset current of the process is very sensitive to the experimental conditions (e.g., scan rate, temperature, type of electrode, etc.). Decomposi-... 

Electrolyzer — Electrochemical cell used for electrolytic processes (-> electrolysis), i.e., the electrochemical decomposition of matter. 

Electrolysis of water — This is a process of electrochemical decomposition of water into -> hydrogen and -> oxygen. Apart from alkaline electrolyzers using 25% KOH solution [i], devices with polymer, or ceramic ion-conducting -> membranes have been developed for industrial applications [ii]. 

TD = thermal decomposition C = ceramic TB = Teflon-bonded RS = reactive sputtering E = electrochemical decomposition or formation SC = single crystal PJS = plasma jet spray. 

Corrosion—the gradual decay of materials—occurs in many ways, all involving electrochemical surface reactions. The essence of it is the electrochemical dissolution of atoms in the surface into the ion-containing film that is in contact with the corroding metal. However, such dissolution has to be accompanied by a counter-reaction and this is often the electrochemical decomposition of water to form hydrogen on the metal surface. If that occurs, the H in the form of minute protons, H, may enter the metal, diffuse about, and cause a weakening ofmetal-metal bonds and hence stress-corrosion cracking. 

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