After reading the attached publication I become not sure about the PEM main functions in MFC. I know that PEM is always for preventing the passing of oxygen from cathode chamber to anode chamber. And if this is the main function, so if I use completely biotic MFC with catalyst other than oxygen (as biocathode), can I remove the PEM and use a single chamber design with bioanode and biocathode electrode? Is it scientifically accepted?
No there are two important roles of PEM
(i) Avoid short circuiting between electons and protons by diffusion cations from anodic chamber
(ii) Also maintain the anaerobic condition in anodic chamber.
For single chamber MFC the concept is slightly different. You may read this documents
http://www.engr.psu.edu/ce/enve/logan/bioenergy/pdf/Engr_499_final_zielke.pdf
The PEM, a any other membrane in closely spaced electrochemical cells, also acts as a separator between both electrodes avoiding short circuits.
Oxygen is not a catalyst, but a reagent, which is reduced to water using the electrons that pass trough the PEM...
PEM is required to separated two chambers because those two posses different potentials. On the other hand, it should be conductive for some ions to sustain the electron balance otherwise the build-up ion require energy to hold them in one chamber.
The PEM such as Nafion serves as the ionic conductive electrolyte for the fuel cell. It also allows only hydrogen difussing through seperate the hydrogen and oxygen in the fuel cell.
There are examples of membraneless MFCs, but it is difficult. Membrane systems are much easier for a first evaluation of a MFC. Then you can study selectivity and see if PEM is necessary.
Dear
http://www.engr.psu.edu/ce/enve/logan/publications/2006-Oh&Logan-AMB.pdf
http://onlinelibrary.wiley.com/doi/10.1002/pat.3383/full
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