Hello Alireza Valipour

It depends what you are trying to demonstrate and how much characterization you wish to perform. It can always be helpful to use different techniques to verify perfomance/behaviour.

You may find the following article interesting, where a RDE was used to investigate the concentration loss and impedance characteristics of anodic biofilms in microbial fuel cells (MFCs):

Article Anodic concentration loss and impedance characteristics in r...

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Hi Alireza Valipour ,

As Jules Lloyd Hammond pointed out, it's best to follow the literature. But, I would advise trying to understand the phenomena behind RDE. What does RDE do and why should anyone care for it.

In short, the theory behind RDE focuses on mass transfer limitations of bringing your reactants to the active site. It would depend entirely on what reaction you're studying at the cathode and limitations of that.

Please remember, the Levich equation only applies to thin films, i.e. simulated 2D structures, it breaks down if your film is too thick or highly porous with an appreciable 3D structure.

It depends on the aim of your work. If you would like to study the performance of the MFCs itself and how the different cathode catalysts could influence this performance. Then the recording the I -V curve of MFCs (Following the standard methods regarding this issue) using different cathode catalysts will be enough. If you would like to know kientically on the level basic of electrochemical study, then you have to do the RDE study. To do RDE measurment, you don't need to have a full MFC ( collecting the anode and cathode in the useul from of MFC whatever in single chamber or two chambers configuration). You need just to have what is called the three electrode electrochemical cell using a rotating disc electrode as the working electrode where you can depoiste your catalysts upon . In this case the electrolyte shoud simulate the same environment as in the real MFC. I mean the medium used within the NYC. Normally the phospgat buffer or the accetate one can be used as electrolyte. Then through recording the LSV or the CV under the hydrodynamic codition of rotating the elctrode at different trotating speeds, you can get more kinetic information about the ORR on your catalysts such as the number of electron involved in the reaction, the kinetic current and a lot of parameters from which you can differentiate the catalytic activity of different catalyts. I recommended you to read well about the RDE technique before you start to use it.

It depends on the aim of your work .

Dear Alireza Valipour,

I think for MFC rotating disc electrode is utmost helpful. you must use it for your electrochemical study.

Microbial biofouling occurs when a biofilm adheres to materials involved in liquid transport causing economic loss through corrosion and drag losses on ship hulls, and in oil and food distribution. A microbial fuel cell (MFC) is a type of microbial electrochemical cell where bacteria consume sugars and other hydrocarbons and excrete CO2, protons and electrons. For a typical biofilm formed during operation of an MFC, rotating disc electrode is utmost helpful, otherwise in redox during the reaction activity cannot be tested as they develop a micro-electro adhered hidden film system itself. Identification will be difficult in biofilm as it adhere to materials. It is mandatory to use disc rotating electrode.

A rotating disk electrode (RDE) is a hydrodynamic working electrode used in a three electrode system. The electrode rotates during experiments inducing a flux of analyte to the electrode. These working electrodes are used in electrochemical studies when investigating reaction mechanisms related to redox chemistry, among other chemical phenomena. The more complex rotating ring-disk electrode can be used as a rotating disk electrode if the ring is left inactive during the experiment. The rotating ring-disk electrode is well suited to investigate for electrochemical reactivity.

If oxygen reduction reactions testing are there to know during electrochemistry EIS, better to go with rotating disc electrode technique. Rotating disc systems can be used to simulate many practical flow systems, like pipe, channel, and porous media flow, while decoupling mass transfer from shear. Rotating disc electrode system to membrane bioreactors and packed bed reactors using theories of flow through porous media at a high rotation rate according to your test system.

[References]:

Adrien Caprani, May de Loizos, and M Nakache. On the effects of particles in suspension on the mass transfer exchange area at a rotating disc electrode. PhysicoChemical Hydrodynamics, 6:567–578, 1985.]

PJ Sonneveld, W Visscher, and E Barendrecht. The influence of suspended particles on the mass transfer at a rotating disc electrode. non-conducting particles. Journal of Applied Electrochemistry, 20(4):563–574, 1990.

Hope it work out for your research work.

Ashish