Electrochemical impedance spectroscopy diffusion coefficient

When the characteristic time for charge diffusion is lower than the experiment timescale, not all the redox sites in the film can be oxidized/reduced. From experiments performed under these conditions, an apparent diffusion coefficient for charge propagation, 13app> can be obtained. In early work choroamperometry and chronocoulometry were used to measure D pp for both electrostatically [131,225] and covalently bound ]132,133] redox couples. Laviron showed that similar information can be obtained from cyclic voltammetry experiments by recording the peak potential and current as a function of the potential scan rate [134, 135]. Electrochemical impedance spectroscopy (EIS) has also been employed to probe charge transport in polymer and polyelectrolyte-modified electrodes [71, 73,131,136-138]. The methods... 

Cadmium atomic layer electrodeposition above reversible Cd2+/Cd potential (underpotential deposition, upd) on bulk tellurium and Te atomic layer predeposited on gold has been characterised with potentiodynamic electrochemical impedance spectroscopy (PDEIS) by variations, with the electrode potential E, of double layer pseudocapacitance Q,u, charge transfer resistance Rrt and Warburg coefficient Aw of diffusion impedance. 

Figure 43 2. Diffusion coefficients far LA in crystalline (a) and disordered (i>) WO3 as obtained from electrochemical transient current measurements and from electrochemical impedance spectroscopy (Strpmme Mattsson [2000]). The diffusion coefficient obtained by impedance spectroscopy is the chemical diffusion coefficient relevant for a specific composition (specified on the upper x axis), while that obtained from the current measurements is an average diffusion coefficient for all compositions lower than the composition value specified on the upper x axis.

Insight into the electroreduction of nitrate ions at a copper electrode, in neutral solution, after determination of their diffusion coefficient by electrochemical impedance spectroscopy. Electrochim Acta 55 7341-7345... 

Estimating diffusion coefficient of probe molecules into polyelectrolyte brushes by electrochemical impedance spectroscopy. 31 7936-7943. 

Electrochemical impedance spectroscopy (EIS) is widely used for characterizing electrochemical systems. By measuring the impedance as a function of frequency, EIS provides a powerful tool for analyzing the performance losses in batteries and fuel cells. For example, Adler et al. have used EIS to identify the causes of fuel cell inefficiencies over a range of experimental operating conditions. KMC simulations can be used to better interpret experimental EIS observations and trace their atomic origins. Diffusion coefficients, electrode resistance, and reaction rates of elementary reactions can be identified with KMC simulations under various applied frequencies, and this information can be used to clarify the connections between EIS peaks or frequencies and the underlying reaction mechanisms. 

S. Diethelm, A. Closset, J. Van Herle, K. Nisancioglu, Determination of chemical diffusion and surface exchange coefficients of oxygen by electrochemical impedance spectroscopy, J. Electrochem. Soc., 2002,149,11, pp. E424-E432. 

Interesting results have also been obtained using y-butyrolactone (GBL) as plasticizer for P(EO-EPI) copolymer. For the electrolyte prepared with GBL, P(EO-EPI)87-13,15 wt% of Nal and h for example, the maximum ionic conductivity changed from 3 x 10 S cm" to 1 x 10 S cm" after addition of 50 wt% of GBL. The apparent diffusion coefficient of ionic species in the electrolyte with and without plasticizer was estimated using complex electrochemical impedance spectroscopy (EIS) and the equivalent circuit (Rg. 10.6) was used to fit the data according to the... 

Conductivity is of course closely related to diffusion in a concentration gradient, and impedance spectroscopy has been used to determine diffusion coefficients in a variety of electrochemical systems, including membranes, thin oxide films, and alloys. In materials exhibiting a degree of disorder, perhaps in the hopping distance or in the depths of the potential wells, simple random walk treatments of the statistics are no longer adequate some modem approaches to such problems are introduced in Section 2.1.2.7. 

In the second subsection we will show how data obtained from electrochemical three-electrode impedance spectroscopy can be used to obtain information about the chemical diffusion coefficient, D, as well as about energy barriers at the... 

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