FlexCell - Electrochemical Test Cells

FlexCell - Test Cell with Three-electrode Set-up

FlexCell is the optimized electrochemical cell, voltammetry test cell, corrosion test cell for electrochemistry with a three-electrode set-up. Working electrode and counter electrode are adjusted parallel. The reference electrode, mainly the mini hydrogen electrode Mini-HydroFlex, is located in a separate reservoir. It measures the potential via a drilled and thus fixed Haber-Luggin capillary which ends directly with a fixed distance to the working electrode.

Flexible regarding to the sample (e.g. metal sheet, foils, gas diffusion electrode) – but rigid where it really counts:

• Fixed and thus defined distance between the working and the counter electrode
• Fixed and thus defined distance between the working and the reference electrode

Planar electrodes, e.g. metal sheets, as well as gas diffusion electrodes (active area 3 cm²) can be installed as the working electrode. The working electrode and the integrated counter electrode (out of inert platinum) are adjusted parallel. This leads to parallel streamlines. The reference electrode is in a separate reservoir so that the streamline flow is not interrupted. A Haber-Luggin capillary connects the reservoir and thus the reference electrode with the major electrolyte area. It ends directly with a fixed, defined distance to the working electrode. Therefore, the potential of the working electrode is always measured at the same point. The working electrode can be supplied with gases as necessary.
This voltammetry test cell and corrosion test cell is chemical resistant and indestructible since it is made of propylene (PP) or polytetrafluorethylene (PTFE). Both variants can be used in a pH range of pH -6 to pH 16. The electrolyte volume is only 30 ml.

Test Cell FlexCell in a Detailed Cross Section

1. Reference electrode: The cell shows a G1/4 thread. With the adapters, the Mini-HydroFlex, the HydroFlex or a silver silver chloride electrode can be mounted tightly sealed.
2. Haber-Luggin capillary: Positioned directly in front of the working electrode and, due to the use of a solid electrolyte, impervious to gas bubbles which could block the capillary.
3. Tubular electrolyte chamber: Ensures an undisturbed field line course. To minimize water vapour losses, the cell is closed by a lid.
4. Counter electrode: Platinum Iridium spiral, 0.3 mm strong. This wire is connected to the lid by a gold-plated banana socket.
5. Working electrode: Your sample is inserted between two seals. Three PTFE pins prevent the seals from shifting. In order for the sample to fit between these pins, the sample has to be cut to the dimensions 30×45 mm.
6. Contacting: Two gold-plated banana sockets 4 mm. These press on the working electrode from the back. If the contact is not enough, the banana socket can be retightened with a wrench. Observe the cleanliness of these plugs. Replace the plugs if the golden coat does not look well anymore.
7. Gas compartment: For gas diffusion electrodes, which require additional gas supply. The gas compartment has two connections. The gas inlet is at the top, the gas outlet at the bottom. The gas compartment is made of a Perspex plate so that the electrode can be observed.
8. Seal: Flat seals and O-ring-seals. Flat seals are suitable for very noble materials, thin samples, or gas diffusion electrodes. The O-ring-seals are suitable for ignoble materials such as steel or aluminium.
9. Gas bubbles outlet: Gas bubbles which arise at the working electrode can rise up at this point and thus do not disturb the measurement.

Protection against Unwanted By-products

Reaction products from the counter electrode can get to the working electrode. Aggressive ions often arise at the counter electrode. Depending on the electrolyte, peroxides, perchlorates, or persulfates can arise. Even small amounts of these lead to corrosion at the working electrode. The test cell FlexCell can be equipped with an intermediate plate with a membrane to separate the working electrode from the counter electrode.

10. Membrane: Separates the working electrode compartment from the counter electrode compartment to protect the working electrode from unwanted by-products. To measure the potential of the working electrode, the reference electrode has to be inserted in the middle cell.

With this set-up you can also measure membrane resistances – for this you will need two reference electrodes. One is located in the analyte compartment, and the other in the actual drilling for the reference electrode.