DigiElch 7 - Overview

DigiElch 7 is a Windows program that computes the electrical current, the concentration profiles and the surface concentrations for any use-defined mechanism comprising an arbitrary number of charge-transfer steps and first- or second-order chemical reactions. The program works for the most common electrode geometries including the simulation of thin layer cell experiments and the exact (two-dimensional) simulation of the electrical current response at band and disk micro-electrodes. Moreover, effects such as adsorption, IR-drop and/or double layer charging can be included in all these simulations. Version 7 includes simulation modules for the following electrochemical methods

  • Cyclic Voltammetry (CV)
  • Square-Wave Voltammetry (SW)
  • Chrono-Amperometry (CA)
  • Multi-sine Impedance (IMP)
  • Fourier-Transform Cyclic Voltammetry (FT)
  • Modules for conducting CV, SW, CA, IMP and FT - experiments using a Gamry Reference 600 potentiostat

This enables the user to do measurements and simulations for the supported electrochemical methods in a perfectly consistent way requiring no data export or import. Real experimental current curves (stored as E/I- or t/I-couples in ASCII-files) can be imported into DigiElch and compared with simulated ones. The determination of the thermodynamic and kinetic parameters involved in the underlying reaction scheme can be accomplished in this way either by "trial and error" ( DigiElch-Standard) or by making use of the non-linear fitting procedure implemented into DigiElch -Professional.

DigiElch - Standard

  • Very fast and accurate simulation of the current response for any user-defined mechanism that can be composed of charge-transfer steps and first- or second-order chemical reactions.
  • 1D simulation of finite- and semi-infinite diffusion processes for the most common regular 1D-electrode geometries.
  • Real 2D-simulations of such user-defined mechanisms for the band and disk electrode.
  • Inclusion of IR-drop and double layer charging where the dependency of the double layer capacity from the electrode potential can be expressed by a fourth-order polynomial.
  • Simulations of termolecular charge-transfer reactions which play an importent role in the  Concerted Proton Electron Transfer (CPET) reactions of the type
          Ox + HA + e = HRed + A-
  • Simulation of adsorption processes where
        - the kinetic of the adsorption processes can be formulated in a way that leads to the Frumkin isotherm under equilibrium conditions
        - CT-reactions may proceed either by direct electron transfer of the adsorbed species or via the desorption pathway
        - the heterogeneous rate constants of any CT-reaction can be linked to the surface coverage of a particular species.
           In this way, CT-reactions proceeding with different speed through the uncovered and covered part of the electrode can be simulated.
        - reactions between adsorbed and desorbed species can be taken into consideration
  • Two different simulation methods:
        - A very fast "fixed grid simulator" providing extremely high exponential convergence towards zero for the simulated flux error.
        - A relatively slow "adaptive grid simulator" that may be useful for simulating accurate concentration profiles and/or for checking
           the accuracy of the fixed grid simulator by an independent method.
  • Options for displaying how the concentration profiles are changing in the course of the simulation.
  • Options for displaying how surface concentrations or surface coverage are changing in the course of the simulation.
  • Options for displaying the fundamental-, second and third-harmonics involved in the FT-CV current curve
  • Options for displaying the envelope of the fundamental-, second and third-harmonics involved in the FT-CV current curve
  • Option for displaying a user-defined harmonics involved in the FT-CV current curve and the envelope of the user-defined harmonics
  • Options for customizing colors and style of the screen display.
  • Multi-core CPU support (process parallelization) for Data Fitting and 2D (micro-electrode)-simulations
  • Export of the screen display in Windows enhanced meta file (*.emf) format.
  • Export of simulated current curves and concentration profiles into ASCII-files. Several formatting options which enable the exported data to be imported into third-party presentation software.
  • Import of experimental (or re-import of simulated) current curves. In this way (and by using the Copy/Paste command) any number of such curves can be simultaneously displayed on the screen for studying the effect of parameter variations simulated curves or for determining parameters yielding the "best fit" between experimental and simulated curves using a "trial and error" strategy.
  • User defined import filters for importing experimental ASCII-data files produced by third-party instruments into DigiElch

DigiElch - Professional

  • Same features as reported above for DigiElch-Standard. Additionally, a non-linear regression procedure can be used for determining the thermodynamic- and kinetic parameters yielding the smallest possible standard deviation between simulated and experimental curves.

Key Features for Conducting Electrochemical Experiments using the Reference 600 Modules

  • Executing experiments with a Reference 600 potentiostat (GAMRY Instruments) from within DigiElch 7 in a way that is perfectly consistent with doing the simulations.
  • The definition of scan segments used in the experiment is accomplished using dialog elements which are identical or very similar to those used for doing simulations.
  • "Run & Fit" i.e. current curves (or impedance data) measured in this way can be directly used for data fitting.
  • One-click determination of uncompensated ohmic resistance, Ru, by measuring the impedance in a potential range where the faradaic current is negligible small.
  • One-click "Measure IR-drop, Adjust IR-Compensation & Run Experiment". That means:
        - the uncompensated ohmic resistance, Ru, is measured as described above.
        - the IR-Compensation is automatically adjusted using the greatest possible value that is just a little bit smaller than the measure value of Ru.
        - the experiment is started.
  • Automatized approach for subtracting the experimental background current from measured current curves.
  • Export of the screen display in Windows enhanced meta file (*.emf) format.
  • Export of experimental current curves into ASCII-files. Several formatting options which enable the exported data to be imported into third-party presentation software.

 


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