When I start MFC (anolyte synthetic water and catholyte phosphate buffer+potasium ferricyanide) I get certain Open circuit potential (OCP) say 0.085 V, when I inoculate anode chamber with my bacterial culture it changes to 0.134 V and further in few days reaches to 0.600 to 0.720 V. After notifying the fall in OCP I fed batch the anode chamber and then again the 0.6 to 0.7 V OCP was achieved. At last after 3 such cycles I closed the circuits with 1 ohm or 100 ohm or 500 ohm resistor but failed to notify any current. So was the OCP only due to chemical changes in the fuel cell, no biofilm was responsible for the same as no current was produced?
P.S. All connection duly checked, no contamination in catholyte, as compare to experimental set ; control set i.e., without bacterial inoculation had very less change in OCP (0.085 to 0075V), media change after fall in potential only.
Kindly guide me on this!
The OCP is, only, an initial (and a powerless) indication for a possible "biofilm" generation[1], with multiple available speculations. Try to measure EIS (if available), with VDC=OCP.
1. Note : Your Quot. is a positive indication for a biofilm generation. Copying your Quot : At last after 3 such cycles I closed the circuits with 1 ohm or 100 ohm or 500 ohm resistor but failed to notify any current.
Probably, I'm not the appropriate person as my knowledge on bio-films are practically negligible but the OCP is the open circuit potential and, then, is the circuit is open no current should be observed, should'n it?
Yes, dear Jordi, for an instance, ONLY, of a OCP over time t, eg. over an instance during a (possibly) growing bio-film. So, applying an ideal Voltmeter or a Vs-source with a value Vs=OCP(to), then no current should be observed. But applying a resistor is another case.
Respected Samaras ,
What does this note means 1. Note : Your Quot. is a positive indication for a biofilm generation. Copying your Quot : At last after 3 such cycles I closed the circuits with 1 ohm or 100 ohm or 500 ohm resistor but failed to notify any current.
If I have not registered any current why are you saying that it is an positive indication of biofilm formation. Kindly elaborate. This will be a great help for me.
If a biofilm is formed it should be of microbes with an ability to donate electrons outside the cell membrane in accordance to the potential difference developed within the anolyte and carbon electrode. If such microbes form a biofilm they should indicate it in the from of some small but measurable current, I suppose.
1) it is a positive indication of (bio)film formation due to the apparent electrodes' modifications ; you say : OCP(t) in few days reaches 0.600 to 0.720 V.
2) However, (possible) physical formation does not mean any charge exchange with your own cell's electrodes, e.g. your external circuit. This is a next (hard) step for R&D.
In short, try to measure EIS (if available), with VDC=OCP. This tool might help us to elaborate both steps.
Respected Samaras ,
I agree Sir, and that is where my topic of interest arises. Mare biofilm formation is not of much use to me as is electron exchange between electrode and microbe is. So now may be i will plan another set and again check the current giving capacity/ electron donating capacity of the biofilm.
Thanks for your support.
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