Potentiostats / galvanostats are designed to perform electrochemical measurements in applications such as corrosion, coatings, batteries, general electrochemistry and many more. Electrochemical Impedance Spectroscopy (EIS) is available as an option for each instrument. This analysis method is used for studies of corrosion, batteries, photovoltaic systems, and in some life science applications. Other options include a wide range of current and voltage boosters.
A potentiostat is primarily used to study redox reactions, i.e. reactions in which electron transfer occur. The reactions take place at the surface of an electrode, the working electrode (WE). A potentiostat controls the difference in electrical potential (voltage) between the working electrode and a reference electrode (RE) in an electrochemical cell. This is done through a negative feedback created by a third electrode (the auxilliary or current electrode, CE).
A galvanostat is more or less the opposite, it maintains a constant current by changing the voltage. This set-up is, for example, used to study the performance and lifespan of rechargeable batteries, to control current flow in electrolysis reactions (such as electroplating or synthesizing chemicals) or corrosion studies.
Potentiostat and galvanostat are usually different settings on the same piece of equipment.
Potentiostats usually have three electrodes, although two or more than three are also possible. The actual measurement is made at the working electrode, where the chemical reaction under investigation takes place on its surface. In corrosion measurements, this electrode is made from a sample of the corroded material. The reference electrode is designed so that no current passes through it, and no chemical reactions take place at its surface. The current electrode is used to close the circuit. (ALT text image: A three-electrode setup for a potentiostat)
The electrodes are hooked up to the potentiostat circuitry. The central part of this is the control amplifier (CA), which is used to keep the voltage between the reference electrode and the working electrode as close as possible to the voltage of the input source (Ei in the simplified circuit diagram). This is necessary to make sure that currents flows only reflect potential variations at the working electrode interface.
In galvanostat mode, the instrument will measure variations in the potential while the current is kept constant. A third mode which is available is Electrochemical Impedance Spectroscopy (EIS), in which a sinusoidal input signal is used (either potential or current), and the dynamic response of the system is measured as a function of frequency.
In order to make the very sensitive potentiostat measurements, it is important to prevent or remove noise. A Faraday cage may be used to block any outside electromagnetic perturbations. Furthermore, software systems are available to remove noise e.g. by using analog filters or software which performs averaging (for random noise).
A potentiostat is vital for the study of reaction mechanisms in electrochemistry, e.g. redox chemistry. Another use is the testing of batteries. Potentiostats can also be used to test for electrochemically active compounds (e.g. drugs, toxins) and microbes in solution. This device is used in many different areas such as domains, as shown in this figure:
The versatility of potentiostats is clear from the wide range of measurements it can perform in both fundamental and applied research, and its accuracy. The energy transition requires measurements with ever higher accuracy and precision, e.g. to develop new chemistry for batteries, or help improve the performance of existing types, but also perform quality control. It is also important to the study of corrosion, e.g. for applications used on or near seawater.
Other applications cover a wide range of important topics, from biofuel cells to the characterization of novel materials or studying classic redox reactions. Sensor research is another field where potentiostats are used.
Electrochemical Impedance Spectroscopy (EIS) also has many applications. It can be used to study corrosion, e.g. in reinforced concrete, but also in electrode kinetics, double-layer studies, batteries, solid-state electrochemistry, and photovoltaic systems.
BioLogic potentiostats are available as single channel or multichannel configuration. They are also scalable, due to their modular design, and can also extremely fast to galvanostat mode, which is useful in battery testing.
Another unique feature of our BioLogic potentiostats is the Bio-Logic’s EC/BT-lab® control software. This allows you adapt settings during measurements, based on your observations, thus building experiments without having to plan all aspects of the process beforehand.
Corrosion is a serious concern, the costs are in the range of USD 2-3 trillion worldwide. Potentiostats are used to analyze the electrochemistry of corrosive processes, such as those caused by oxidants like sulphate or oxygen. Reduction of corrosion could save hundreds of billions.
One way to prevent corrosion is the applications of protective coatings. Potentiostats are used widely in research towards such coatings, and offer a ‘macro’ view of corrosion, which helps to better understand local electrochemical processes occurring during this process. To get a more detailed, ‘micro’ view, a scanning probe workstation can be used to study impedance distribution in materials. This is done using the Localized Electrochemical Impedance Spectroscopy (LEIS) technique.
Batteries have become extremely important to everyday life, from your phone to your car or the storage of surplus electricity from your solar panels. Potentiostats help to characterize all the parts of a battery cell, and can also to collect data on its performance. This is done through charge/discharge cycles. Potentiostats are vital to characterize battery quality, for example during ageing. This is done by quantifying the internal resistance over the battery lifespan, using Electrochemical Impedance Spectroscopy (EIS).
A basic function of potentiostats is the analysis of redox reactions. For example, they can be used to characterize species or electrochemical processes, which is done using the cyclic voltammetry technique of BioLogic software EC-Lab®. Potentiostats are also used to study the process of CO2 electrolysis, a process that will convert this greenhouse gas into valuable chemicals through reduction.
Crucial to the function of a potentiostat / galvanostat and applications like electrochemical impedance spectroscopy is the software. All our BioLogic instruments are controlled by the very versatile EC-Lab® software, to provide a range of measurement modes, with different modular techniques with wait and loop options to create complex experimental chain. This software is also able to control several potentiostats from a single interface view.
A wide range of quality indicators will help users to validate their EIS experiments, with regard to linearity, non-stationarity or noise.
Finally, in contrast to many other systems, it is possible to ‘Modify on the fly’, i.e. change parameter settings during an experiment when results are not as expected.
