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The main function of a fuel cell potentiostat is to measure the electrical current and voltage of a fuel cell as it operates, and furthermore to provide precise control over the electrical potential applied to the cell. This device is therefore a mainstay of fuel cell testing, but also of control systems used in actual operation.
The fuel cell potentiostat allows researchers and engineers to study different fuel cell test loads under various operating conditions, so as to optimize fuel cell design.
Forming an important part of a fuel cell test station, the potentiostat is used to control the electrical potential applied to a fuel cell, while a galvanostat is used to control the electrical current applied to a fuel cell. Both instruments are used to study the performance of fuel cells, but they operate in different modes. In an aim to measure energy density of a fuel cell, potentiostat designs must be integrated and adapted accordingly. This is often done by combining the potentiostat and the galvanostat into one single unit. Fuel cell energy density is then derived from inputs of both potential and current in real time.
In a fuel cell, two modes can be regulated: the cathodic mode and the anodic mode. The cathodic mode refers to the reduction reaction that occurs at the cathode, while the anodic mode refers to the oxidation reaction that occurs at the anode. By controlling the electrical potential applied to the fuel cell, the potentiostat can regulate the rate of these reactions and study their effect on the overall performance of the fuel cell.
Function modes of a fuel cell potentiostat
There are several different function modes that a potentiostat can operate in, including open-circuit voltage (OCV), zero-resistance amperometry (ZRA), and electrochemical impedance spectroscopy (EIS).
- In OCV mode, the potentiostat measures the open-circuit voltage of the fuel cell, which is the voltage across the cell when no current is flowing. This can provide information about the overall performance of the cell and the efficiency of the reactions occurring within it.
- In ZRA mode, the potentiostat measures the electrical current flowing through the fuel cell as the electrical potential is varied over a wide range. This can provide information about the rate of the reactions occurring at the anode and cathode and the overall efficiency of the fuel cell.
- In EIS mode, the potentiostat applies a small AC signal to the fuel cell and measures the electrical impedance of the cell as a function of frequency. This can provide information about the electrical and chemical processes occurring within the cell and can help researchers identify problems or limitations in the cell’s design.
Key specifications
When selecting a potentiostat for fuel cell applications, there are several key specifications to consider. These include the accuracy and precision of the measurements, the range of electrical potentials and currents that the instrument can handle, the speed and resolution of the measurements, and the durability and reliability of the instrument. Other important factors to consider include the user interface and software capabilities, the availability of technical support and training, and the overall cost of the instrument.
Measuring the impedance of fuel cells
To understand how a fuel cell works and how impedance can be measured using an electric load, it is helpful to understand the basic principles of fuel cell operation.
In a fuel cell, two electrodes (the anode and cathode) are separated by an electrolyte. A fuel, such as hydrogen or methanol, is supplied to the anode, where it undergoes an oxidation reaction to produce protons and electrons. The protons are transported through the electrolyte to the cathode, where they react with oxygen and electrons to produce water.
As the protons and electrons are generated at the anode, they flow through an external circuit, generating an electrical current. This current can be measured using a potentiostat, which applies a controlled electrical potential to the fuel cell and measures the resulting current.
Impedance is a measure of the resistance to the flow of electrical current in a circuit. It can be measured using an electric load, which is a device that consumes electrical energy and generates a measurable current and voltage.
To measure the impedance of a fuel cell using an electric load, the potentiostat applies a small AC signal to the cell and measures the resulting current and voltage. The impedance of the fuel cell is then calculated from the ratio of the voltage to the current. This can provide valuable information about the performance of the fuel cell and the efficiency of the reactions occurring within it. An integrated potentiostat can supply this data to the fuel cell controller on an on-going basis during operation.
The potential range that should be selected for fuel cell applications depends on the specific requirements of the application and the type of fuel cell being used. In general, potentiostats that can handle a wide range of potentials are more versatile and can be used in a wider range of applications.
Summary
The fuel cell potentiostat is an important part of the instrumentation needed for studying and optimizing the performance of fuel cells. They allow researchers and engineers to control and measure the electrical potential applied to the cell and to study the resulting reactions and processes occurring within the cell. When selecting a potentiostat for fuel cell applications, it is important to consider key specifications such as accuracy, range, and reliability, as well as other factors, such as user interface and cost.
A combined fuel cell potentiostat/galvanostat is typically integrated into fuel cell test systems encompassing a variety of monitoring equipment within a single cost-effective benchtop unit.
Last update: 04.04.2023