Faradaic efficiency current

OS 86] [R 29] [P 66] The Faradaic current efficiency, the electrical charge equivalent for conversion as a fraction of the total electrical charge, was measured for a... 

Figure 4.95 Faradaic current efficiency as electrical charge equivalent for conversion of D-gluconic acid given for two values of average current density. The symbols represent measured conversion and the solid and dashed lines calculated results [65. ...

Espinasse G., Peyrard M., Nicolas F. Caire J.P., Effect of hydrodynamics on Faradaic current efficiency in a fluorine electrolyser, Jal of Applied Electrochemistry, 37, pp. 77-85, 2007. 

For a photocurrent output of 10 mA cm 3.2 X 10 C cm are passed across the photoelectrochemical interface during ten years of operation. During this span, assuming a faradaic current efficiency of... 

The current efficiencies for CO2 formation and formic acid formation during poten-tiodynamic formaldehyde oxidation, calculated from the data in Fig. 13.3b as the ratio of the partial currents to the total faradaic current (in %), are plotted in Fig. 13.4a. 

Figure 13.6 Potential-step electro-oxidation of formaldehyde on a Pt/Vulcan thin-film electrode (7 p,gpt cm, geometric area 0.28 cm ) in 0.5 M H2SO4 solution containing 0.1 M HCHO upon stepping the potential from 0.16 to 0.6 V (electrolyte flow rate 5 pL at room temperature). (a) Solid line, faradaic current transients dashed line, partial current for HCHO oxidation to CO2 dotted line, difference between the net faradaic current and that for CO2 formation, (b) Solid line, m/z = 44 ion current transients gray line potential-step oxidation of pre-adsorbed CO derived upon HCHO adsorption at 0.16 V, in HCHO-free sulfuric acid solution, (c) Current efficiency transients for CO2 formation (dashed line) and formic acid formation (dotted line).

The current efficiencies for the different reaction products CO2, formaldehyde, and formic acid obtained upon potential-step methanol oxidation are plotted in Fig. 13.7d. The CO2 current efficiency (solid line) is characterized by an initial spike of up to about 70% directly after the potential step, followed by a rapid decay to about 54%, where it remains for the rest of the measurement. The initial spike appearing in the calculated current efficiency for CO2 formation can be at least partly explained by a similar artifact as discussed for formaldehyde oxidation before, caused by the fact that oxidation of the pre-formed COacurrent efficiency. The current efficiency for formic acid oxidation steps to a value of about 10% at the initial period of the measurement, and then decreases gradually to about 5% at the end of the measurement. Finally, the current efficiency for formaldehyde formation, which was not measured directly, but calculated from the difference between total faradaic current and partial reaction currents for CO2 and formic acid formation, shows an apparently slower increase during the initial phase and then remains about constant (final value about 40%). The imitial increase is at least partly caused by the same artifact as discussed above for CO2 formation, only in the opposite sense. 

For the operating voltage at the optimum power point Vp and the Faradaic current for water splitting of /p, the overall solar to hydrogen generation PV electrolysis efficiency is given by... 

Faradaic efficiency The quotient of faradaic current to total current passed. 

Current-potential curves obtained under steady state conditions are called polarization curves. If two or more faradaic processes occur at the electrode, the fraction of current (ir) driving the rth process is the instantaneous current efficiency. Over a period of operating time the fraction of the total number of coulombs used in the rth process ( r) is related to the overall current efficiency of that process (OCE), i.e. 

Current efficiency — (-> faradaic efficiency, current yield) is the ratio between the partial current density j, which corresponds to a given - electrode reaction and/or... 

Current yield - current efficiency, -+faradaic efficiency... 

Faradaic efficiency (or coulometric efficiency) — Relates the moles of product formed in an -> electrode reaction to the consumed -> charge. The faradaic efficiency is 1.00 (or 100%) when the moles of product correspond to the consumed charge as required by -> Faraday s law. See also -> current efficiency, -> coulometry. 

When organic solvents are used for anodic fluorination, anode passivation (the formation of a nonconducting polymer film on the anode surface that suppresses faradaic current) takes place very often, which results in low efficiency. Moreover, depending on the substrates the use of acetonitrile can yield an acetoamidation byproduct. To prevent acetoamidation and anode passivation, Meurs and his coworkers used an EtaN 3HF ionic liquid as both a solvent and supporting electrolyte (also a fluorine source) for the anodic fluorination of benzenes, naphthalene, olefins, furan, benzofuran, and phenanthroline. They obtained corresponding partially fluorinated products in less than 50% yields (Scheme 8.2) [11]. 

Consider a hypothetical case in which the faradaic efficiency is inversely proportional to the current efficiency. We could then write... 

If a defect-free molecular assembly covers an electrode surface completely, the assembly is an efficient electrochemical blocker [23, 30, 46, 47]. Electron transfer through the SAM to a solution redox probe is substantially slower than the rate of diffusion of the probe to the surface, and the voltammetric response is a quasiexponential increase in Faradaic current resulting from electron transfer across the chains of the SAM [30, 46]. This type of response qualitatively supports the presence of a monolayer low in defect sites. A more quantitative measure of the EBE of a modified electrode is expressed as the percentage of total blocking achieved using a bare electrode as the standard [48] ... 

As a measure for this efficiency, clearly the cell voltage of the fuel cell compared to that of the electrolysis is a first tool. Nowadays we have values of 0.8-1.8 V, that is, the ratio is 0.45. In the future, 0.9-1.2 V may be achieved, that is, 0.75. But this value is somewhat optimistic, if the Faradaic losses (current efficiencies) and the energy losses resulting from electrolysis and fuel cell operation are taken into account, too, amounting surely to an additional loss of 10-15%. 

Electrocatalysis at metal electrodes in aqueous (1.2) and non-aqueous ( ) solvents, phthalocyanine ( ) and ruthenium ( ) coated carbon, n-type semiconductors (6.7.8),and photocathodes (9,10) have been explored in an effort to develop effective catalysts for the synthesis of reduced products from carbon dioxide. The electrocatalytic and photocatalytic approaches have high faradaic efficiency of carbon dioxide reduction (1,6). but very low current densities. Hence the rate of product formation is low. Increasing current densities to provide meaningful amounts of product, substantially reduces carbon dioxide reduction in favor of hydrogen evolution. This reduction in current efficiency is a difficult problem to surmount in light of the probable electrostatic repulsion of carbon dioxide, or the aqueous bicarbonate ion, from a negatively charged cathode (11,12). 

When two or more faradaic reactions can occur simultaneously at an electrode, the fraction of the total current (/total) going to the rth process is called the instantaneous current efficiency ... 

The Faradaic current is a measure of the rate of all the electrochemical reactions occurring at the working electrode. We say that there is 100% Faradaic efficiency if the only reaction occurring is... 

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