I am getting all straight lines in my polarization curve. Can this mean something significant or its an experimental error ?
The polarisation curve for a mfc means the graph of U=f(I), i.e. U=E-r I (*), where U=voltage measured on a resistance load, E=electromotive force of the mfc, r=internal resistance of mfc, I= current intensity through the external resistance.From the graph, which must be linear(see (*)), we can find r as the slope of the graph, and the E as the intersection of the graph with y axis.
These papers should help you-
1/ http://www.engr.psu.edu/ce/enve/logan/publications/2011-Watson&Logan-ElectrochemComm.pdf
2/ http://core.ac.uk/download/pdf/102229.pdf
The second link gives a detailed explanation of Polarization curves and their interpretation.
Dear Philem
Thanks for your interesting question, as we produce polarization curve we quickly pass! I am absolutely agree with the simple equations discussed by other research scientists. In fact you are operating MFC and you wish to monitor voltage and current as you are recording the performance of little electro cell while microorganisms are liberating sufficient electrons; as life goes on smooth for the living cells. Since you are using anode the material and contact surface of anode, plus the correct anode configuration transmitting electrons. Therefore, you use a normalized term that is current density. In fact you wish to obtain maximum current that corresponds to maximum voltage. Let us have a test run on your MFC while your data logger recording current and voltage with respect to time. As it starts, the left side of the above shown curve demonstrates along with cell growth and the right side shows as voltage gradually drops and your nutrients are depleted. The best explanation in terms of cell electrochemical activities would be polarization curve. It can shows your deliver voltage with respect to current or current density. Please keep in mind about internal resistances of MFC, such term can lower your MFC's performance. If you have instant recorder then you never get straight line. Please check and see reliability of your MFC system.
Thank you all for your suggestions. I was hoping to get three differentiated regions in my polarisation curve so to define the quantity of activation , ohmic and mass loss. I will do another round of reading for more information. Thank you again.
If you could share some details of your experimental setup and the values of resistors used for performing characterization it might be possible to provide an explanation for why the polarization curves are the way they are.
Mariam Khalid, no trend lines were added I the analysis of my data. It was a trail experiment for a small project.
Dear Pushpa,
I hope you already get answer by now. I want to add something here. It is not surprising to see such trend in fuel cell characterization. However, in real time measurement it is quite different than what it looks like. This means there is not much difference in different loss in you MFC which is governed by many factors.
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