Image made using the COMSOL Multiphysics® software and is provided courtesy of COMSOL.
Cyclic voltammetry is a common technique for electrochemical analysis in which the potential at the working electrode is swept over a voltage range while the current is recorded.
The Electrochemistry Module expands the possibilities in designing, understanding, and optimizing electrochemical systems through accurate simulation. This product offers significant benefit to researchers in the lab or to the industrial electrochemical engineer. Capabilities such as modeling electrochemical reaction mechanisms, mass transport, and current density distributions enable efficient simulation for applications including electrolysis, electrodialysis, electroanalysis, electrochemical sensors, and bioelectrochemistry.
The Electrochemistry Module covers a wide range of applications involving electrochemical reactions. This is accomplished through interfaces for primary, secondary, and tertiary current distributions; electroanalysis; flow in free and porous media; heat transfer; heterogeneous and homogeneous chemical reactions; and material transport in dilute and concentrated solutions. Possible applications include the study and design of chlor-alkali and chlorate electrolysis, water electrolysis for hydrogen and oxygen production, waste water treatment, desalination of seawater, fundamental electrochemical studies in electrocatalysis and electroanalysis, and sensors for glucose, pH, hydrogen, and other gases.
Cyclic voltammetry is a common analytical technique for investigating electrochemical systems. In this method, the potential difference between a working electrode and a reference electrode is swept linearly in time from a start potential to a vertex potential, and back again. The current-voltage waveform, called a voltammogram, provides information about the reactivity and mass transport properties of an electrolyte.
The purpose of the app is to demonstrate and simulate the use of cyclic voltammetry. You can vary the bulk concentration of both species, transport properties, kinetic parameters, and the settings of the cyclic voltammeter.
The electrochemical cell shown in this model can be regarded as a unit cell of a larger wire-mesh electrode that is common in many industrial processes. One of the most important aspects in the design of electrochemical cells is the current density distributions in the electrolyte and electrodes. Non-uniform current density distributions can be detrimental for the operation of electrochemical processes. In many cases, the parts of an electrode that are subjected to a high current density can degrade at a faster rate. Knowledge of the current density distribution is necessary to optimize the utilization of the electrocatalysts that are typically comprised of expensive noble metals. Non-uniform deposition and consumption, unnecessarily high overvoltages, energy losses and possible unwanted side-reactions represent effects that should be minimized. This example simulates the primary, secondary, and tertiary current density distributions of an arbitrary electrochemical cell with wire electrodes. The current density distributions are investigated in succession so as to also demonstrate good working practices by gradually introducing complexity when modeling electrochemical cells.
In the diffuse double layer and within the first few nanometers of an electrode surface, the assumption of electroneutrality is not valid due to charge separation. Typically, the diffuse double layer may be of interest when modeling very thin layers of electrolyte including those in electrochemical capacitors and microelectrodes. This example shows how to couple the Nernst-Planck equations to Poisson’s equation, in order to consider this deviation from electroneutrality. A Stern layer with constant capacity is used to derive surface charge boundary conditions for Poisson’s equation. This 1D model reproduces the results published in literature.
The chlor-alkali membrane process is one of the largest in industrial electrolysis with the production of roughly 40 million metric tons of both chlorine and caustic soda per year. Chlorine is used predominantly for the production of vinyl chloride monomer, which in turn is used for the production of poly vinyl chloride (PVC). Current density in membrane-cell technology has increased dramatically during the last decade as the membranes themselves have improved. This results in lower investment costs for greater production. However, the increase in current density implies an increase in power consumption if nothing is done to dampen the voltage increase. Advances in cell design including increased internal convection, decreased ohmic losses, and better membranes have allowed for large increases in current density with small increases in cell voltage. This example describes the current-density distribution in realistic anode and cathode structures in a membrane cell.
Electrodialysis is a separation process for electrolytes based on the use of electric fields and ion selective membranes. Some common applications of the electrodialysis process are:
– Desalination of process streams, effluents, and drinking water
– pH regulation in order to remove acids from, for example, fruit juices and wines
– Electrowinning of precious metals
This tutorial demonstrates the basics of electrodialysis in a desalination cell that removes sodium chloride from a dilute water solution and into a more highly concentrated solution.
This model incorporates the transport and electrolytic reaction in the treatment of tumor tissue.
Oxygen evolution at the anode produces protons, which lowers the pH, while chlorine production also leads to lowered pH through the hydrolysis of chlorine. One effect of a low pH is the permanent destruction of haemoglobin in the tissue, resulting in the eradication of tumor tissue.
This model uses the Nernst-Planck Equations interface to predict the transport and reaction in the electrolysis of tumor tissue in a liver.
Electrochemical impedance spectroscopy (EIS) is a common technique in electroanalysis. It is used to study the harmonic response of an electrochemical system. A small, sinusoidal variation is applied to the potential at the working electrode, and the resulting current is analyzed in the frequency domain.
The real and imaginary components of the impedance give information about the kinetic and mass transport properties of the cell, as well as the surface properties through the double layer capacitance.
The purpose of the Electrochemical Impedance Spectroscopy analysis app is to understand EIS, Nyquist, and Bode plots. The app lets you vary the bulk concentration, diffusion coefficient, exchange current density, double layer capacitance, and the maximum and minimum frequency.
