Electrochemical cell, cyclic voltammetry

In order to improve the fuel utilization in a Direct Alcohol Fuel Cell (DAFC) it is important to investigate the reaction mechanism and to develop active electrocatalysts able to activate each reaction path. The elncidation of the reaction mechanism, thus, needs to combine pnre electrochemical methods (cyclic voltammetry, rotating disc electrodes, etc.) with other physicochemical methods, such as in situ spectroscopic methods (infrared and UV-VIS" reflectance spectroscopy, or mass spectroscopy such as EQCM, DEMS " ), or radiochemical methods to monitor the adsorbed intermediates and on line chromatographic techniques"" to analyze qnantitatively the reaction products and by-products. 

Method Abs, chemical reduction, monitored by absorption spectroscopy CD, chemical reduction, monitored by CD spectroscopy CD/OTTLE, electrochemical reduction using an optically transparent thin layer (OTTLE) cell, monitored by CD spectroscopy CV, cyclic voltammetry EPR, chemical reduction, monitored by EPR. 

Cyclic voltammetry was performed on precursor polymer thin films cast on platinum electrodes in order to assess the possibility of electrochemical redox elimination and consequently as an alternative means of monitoring the process. All electrochemical experiments were performed in a three-electrode, single-compartment cell using a double junction Ag/Ag+(AgN03) reference electrode in 0.1M... 

Figure 2.15 Schematic representation of the equipment necessary to perform linear sweep voltammetry LSV) or cyclic voltammetry CV). WFG waveform generator, P potentiostat, CR chart recorder, EC electrochemical cell, WE working electrode, CE counter electrode, RE...

Aniline, methyl aniline, 1-naphthylamine, and diphenylamine at trace levels were determined using this technique and electrochemical detection. Two electrochemical detectors (a thin-layer, dual glassy-carbon electrode cell and a dual porous electrode system) were compared. The electrochemical behavior of the compounds was investigated using hydrodynamic and cyclic voltammetry. Detection limits of 15 and 1.5nmol/l were achieved using colourimetric and amperometric cells, respectively, when using an in-line preconcentration step. 

A Ru(0001) sample, with vacuum deposited Cu, has been characterized by cyclic voltammetry by transferring to an electrochemical cell (16). Figures 4e-4h shows the anodic stripping curves for four different coverages of Cu. A single stripping peak was observed at +110 mV for 0.6 ML Cu and shifted to +145 mV for 5.2 ML Cu. This peak represents the removal of the first monolayer of Cu or Cu in direct contact with the Ru surface. The curve for 5.2 ML Cu shows an additional peak at -20 mV for the stripping of multilayer Cu. 

Figure 16.4 A three-electrode electrochemical cell used in cyclic voltammetry experiments. Adapted from [335],...

The advantage of using a sacrificial anode has been clearly pointed out. Magnesium was found to be the most convenient, the oxidation of which produces Mg ions which can enter the catalytic cycle to cleave the nickela-cycle intermediate and liberate Ni for further catalytic cycles (Scheme 7). Such a mechanism has been substantiated on the basis of the formation of the nickelacycle and its characterization by cyclic voltammetry. In the absence of Mg (reactions conducted in a divided cell in the presence of ammonium ions) the nickelacycle does not transform and the reaction stops when all the starting nickel compound has been reacted. Upon addition of MgBr2 to an electrochemically prepared solution of the nickelacycle, Ni(II) is recovered [114]. 

The cycle life of a rechargeable battery depends on the long-term reversibility of cell chemistries, and the electrochemical stability of the electrolyte plays a crucial role in maintaining this reversibility. In electrochemistry, there have been numerous techniques developed to measure and quantify the electrochemical stability of electrolyte components, and the most frequently used technique is cyclic voltammetry (CV) in its many variations. 

Electrochemically generated nickei(lll) oxide, deposited onto a nickel plate, is generally useful for the oxidation of alcohols in aqueous alkali [49]. The immersion of nickel in aqueous alkali results in the formation of a surface layer of nickel(ll) oxide which undergoes reversible electrochemical oxidation to form nickel(lll) oxide with a current maximum in cyclic voltammetry at 1.13 V vj. see, observed before the evolution of oxygen occurs [50]. This electrochemical step is fast and oxidation at a prepared oxide film, of an alcohol in solution, is governed by the rate of the chemical reaction between nickel oxide and the substrate [51]. When the film thickness is increased to about 0.1 pm, the oxidation rate of organic species increases to a rate that is fairly indifferent to further increases in the film thickness. This is probably due to an initial increase in the surface area of the electrode [52], In laboratory scale experiments, the nickel oxide electrode layer is prepared by prior electrolysis of nickel sulphate at a nickel anode [53]. It is used in an undivided cell with a stainless steel cathode and an alkaline electrolyte. 

For the electrochemical measurements reported herein, all cyclic voltammetry measurements are performed in CH2C12 with 0.1 M tetra-n-butylammonium tetrafluoroborate (Bu4NBF4) as supporting electrolyte, while measurements in CH3CN use 0.1 M tetra-ethylammonium perchlorate. Cyclic voltammetry measurements are performed in a three-electrode, one-compartment cell equipped with a Pt working electrode, a Pt auxiliary electrode, and a saturated sodium chloride calomel (SSCE) reference electrode. E1 2 = (Ep.a + Ep.c)/2 AEP = Ep,e - Ep,a-Ei/2 and AEP values are measured at 100 mV/sec. Ferrocene is used as a reference in the measurement of the electrochemical potentials. 

Cyclic voltammetry is one such electrochemical technique which has found considerable favour amongst coordination chemists. It allows the study of the solution electron-transfer chemistry of a compound on the sub-millisecond to second timescale it has a well developed theoretical basis and is relatively simple and inexpensive. Cyclic voltammetry is a controlled potential technique it is performed at a stationary microelectrode which is in contact with an electrolyte solution containing the species of interest. The potential, E, at the microelectrode is varied linearly with time, t, and at some pre-determined value of E the scan direction is reversed. The current which flows through the cell is measured continuously during the forward and reverse scans and it is the analysis of the resulting i—E response, and its dependence on the scan rate dE/dt, which provides a considerable amount of information. Consider, for example, the idealized behaviour of a compound, M, in an inert electrolyte at an inert microelectrode (Scheme 1). 

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