How to Model Ion-Exchange Membranes and Donnan Potentials

Henrik Ekström August 29, 2018

Ion-exchange membranes are widely employed within the field of electrochemical engineering. In polymer electrolyte fuel cells and vanadium flow batteries, they are used to conduct ions and at the same time prevent reactants and electrons from crossing between the two flow compartments. The ability to promote the passage of ions of either positive or negative charge is also used in electrodialysis for cleaning water from ions. In this blog post, we will explore the ion-selective capabilities of ion-exchange membranes.

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Thomas Forrister July 3, 2018

In electrochemistry, it’s common to use a microdisk as the working electrode in an analytical technique known as cyclic voltammetry. However, unlike with a macroelectrode, diffusion at a microelectrode occurs very fast on the timescale of the experiment. To simplify the analysis, we can use an approximation that assumes the microdisk has stationary diffusion properties on the timescale of the voltammetry study — eliminating the need for a time-dependent model.

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Edmund Dickinson September 5, 2017

Precision machining and quality of surface finish are major concerns for manufacturers of metal parts. The promise of a contactless method to machine surfaces with submillimeter precision and a clean surface, on metals of almost any hardness, might seem too good to be true. However, such a method, pulsed electrochemical machining (PECM), was the focus of a detailed investigation using numerical modeling presented at the COMSOL Conference 2016 Munich.

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Caty Fairclough August 15, 2017

Zone electrophoresis separates different species in a sample into distinct well-resolved peaks, giving scientists the ability to analyze substances like proteins and nucleic acids. Improving this electrophoretic separation technique requires us to accurately model the transport and separation of these species. Here, let’s look at how the COMSOL Multiphysics® software can be used to simulate the movement of species during zone electrophoresis.

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Bridget Cunningham March 10, 2017

While reverse electrodialysis (RED) is a promising source of renewable energy, it can be a challenging process to analyze. The performance of RED units is affected by the physical phenomena that occur when converting salinity gradient energy into electric current. To address this, one team of researchers used a novel approach to model such systems in the COMSOL Multiphysics® software. Their multiphysics model and subsequent simulation studies provide further insight into designing and optimizing RED units.

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Edmund Dickinson February 9, 2017

Electrochemical impedance spectroscopy is a versatile experimental technique that provides information about an electrochemical cell’s different physical and chemical phenomena. By modeling the physical processes involved, we can constructively interpret the experiment’s results and assess the magnitudes of the physical quantities controlling the cell. We can then turn this model into an app, making electrochemical modeling accessible to more researchers and engineers. Here, we will look at three different ways of analyzing EIS: experiment, model, and simulation app.

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Scott Smith August 24, 2016

Resistive and capacitive effects are fundamental to the understanding of electrochemical systems. The resistances and capacitances due to mass transfer can be represented through physical equations describing the corresponding fundamental phenomena, like diffusion. Further, when considering the resistive or capacitive behavior of double layers, thin films, and reaction kinetics, such effects can be treated simply through physical conditions relating electrochemical currents and voltages. Lastly, resistances and capacitances from external loading circuits can easily be represented in the COMSOL Multiphysics® software.

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Edmund Dickinson August 14, 2014

Diabetes is an incurable global killer: the World Health Organization estimates 350 million diabetics worldwide, with an average annual fatality rate close to 1%. Fortunately, modern medical science enables diabetics to manage their glucose levels and intake, so many countries have seen greatly reduced danger of the disease. Many diabetics must track their glucose levels throughout the day, requiring an accurate method for measuring the concentration of glucose in blood. For modern sensor designs, the method of choice is electrochemistry.

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Melanie Pfaffe February 10, 2014

When designing electrochemical cells, we consider the three classes of current distribution in the electrolyte and electrodes: primary, secondary, and tertiary. We recently introduced the essential theory of current distribution. Here, we illustrate the different current distributions with a wire electrode example to help you choose between the current distribution interfaces in COMSOL Multiphysics for your electrochemical cell simulation.

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Edmund Dickinson February 7, 2014

In electrochemical cell design, you need to consider three current distribution classes in the electrolyte and electrodes. These are called primary, secondary, and tertiary, and refer to different approximations that apply depending on the relative significance of solution resistance, finite electrode kinetics, and mass transport. Here, we provide a general introduction to the concept of current distribution and discuss the topic from a theoretical stand-point.

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Phil Kinnane June 12, 2013

My colleague, Edmund Dickinson, recently blogged about cyclic voltammetry, and how this can be modeled. It was a fantastic blog entry, as it really described the application, and how to implement such models in COMSOL Multiphysics. While Edmund has a background in electroanalysis, where cyclic voltammetry, potentiometry, and electrochemical impedance are important tools, I had a different but similar life before COMSOL, working within industrial electrolysis. For both of us, the new Electrochemistry Module would have been the perfect tool […]

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