By Pawel Jerzy Wojcik
If you want to cite this blog post use: Wojcik, P.J. (2017). Troubleshooting Electrochemical Cell. [online] redox.me Available at: https://redox.me/blogs/good-measurement-practices/troubleshooting-electrochemical-cell [Accessed Date Accessed].
This post concerns a situation in which the electrochemical setup based on a cell does not seem to be producing the proper response. The specific guidelines for checking an electrochemical system and isolating the problem may be typically found in setup manual. The following post has a more general character and is based on electrochemistry handbooks [1].
Let’s consider the setup intended for CV measurements in a 3-electrode configuration. It consists of metal wire counter electrode, reference electrode and sample of interest as working electrode (either solid electrode or a thin film deposited on a substrate).
1. Dummy cell test
With the electrochemical instrument (e.g. potentiostat) turned off, disconnect the cell and replace it with a 10 kOhm resistor (i.e. dummy cell), with the reference and counter electrode leads connected together on one side of the resistor and the working electrode lead connected to the other side. Perform a CV scan from +0.5 to -0.5 V with the scan rate of 100 mV/s. The resulting scan should be a straight line that intersects the origin with maximum currents of +/-50 uA.
a) The correct response is obtained. This means the electrochemical instrument and the leads and connections are OK, and the problem lies in the electrochemical cell. (Go to 2.)
b) An incorrect response is obtained. There is a problem with the instrument or leads. (Go to 3.)
2. Testing the cell in 2-electrode configuration
Reconnect the cell, but connect both the reference and counter electrode leads to the counter electrode and the working electrode lead to the working electrode. Run the CV scan, as previously. The response should now resemble a typical voltammogram.
a) This response is obtained. The problem lies with the reference electrode, which is one of the most common sources of problems. Check to make sure the electrode frit is not clogged and is immersed in the solution, that no air bubble is close to the frit blocking the solution access to it, and that the pin of the reference electrode is making proper contact. If none of these problems is found, replace the reference electrode with a pseudo-reference electrode and see if a good voltammogram is obtained. If so, replace the reference electrode.
b) This response is not obtained. Make sure both the counter and working electrodes are immersed in the solution and that the internal electrode leads are intact (use an ohmmeter to check continuity between lead and electrode). If the response obtained is generally satisfactory, but the waves are drawn out or otherwise strange, the problem may be with the working electrode surface. Go to 4.
3. Leads replacement
Disconnect the leads between the instrument and the cell and replace with another set of leads or check the continuity between the instrument connector and the cell connection on either side of each lead (working, reference, counter). If the problem is not in the leads, then the instrument is at fault and must be serviced.
4. Working electrode checkup
The problem may be with the working electrode surface. For example, it may contain a layer of polymer or adsorbed material that partially blocks or changes its electrochemical response. In general, solid electrodes (working and counter) can be reconditioned by polishing, chemical, electrochemical or thermal treatment. Please contact the electrode supplier to get an information on proper conditioning. In case of thin film material used as working electrode, the problem may be related to the detachment of the film from the current collector, its dissolution in the electrolyte solution or its insulating properties.
5. Reduction of Noise
The problem with an excessive noise can be caused by poor contacts either to the electrodes or at the instrument connector (rust or tarnish). It can be corrected by leads contact polishing or their replacement and placing the cell in a Faraday cage.
References
[1] Bard. A.J. et al. 2001. Electrochemical methods. Fundamentals and Applications. Danvers: John Wiley & Sons, Inc.
Please, note that the content of this article is constantly being updated to cover the topic in the possibly most reliable way. At the same time, we are doing our best to keep it in line with the state-of-the-art research.
