Two-chamber reactors with soluble catholytes or poised potentials

4 Two-chamber reactors with soluble catholytes or poised potentials 

Permanganate catholyte. A simple H-type of reactor made of two plastic bottles and 

Poised potential reactors. In a reactor with oxygen as the electron acceptor at the cathode, the working potential is typically ca. 0.25 V, with the anode at ca. -0.2 V, producing 0.45 V (see pig. 3,1 ) In a poised potential experiment, the anode potential can be set at any value using a potentiostat. Once that is done, the bacteria see a terminal 

When a poised potential is used, energy is put into the system. For example, if the working potential for the anode was -0.3 V but the potential was poised at 0.2 V, then the input power would be P = 0.5 /, where I is the current achieved in the experiment. Thus, power is input into this system directly in a non-sustainable manner, as opposed to indirectly using the chemical energy of catholytes such as ferricyanide. Another potential disadvantage of this set up is that H2 gas produced in the cathode chamber. If this gas diffuses back into the anode chamber, it can become another substrate for the bacteria which can artificially raise the Coulombic efficiency or power production. 

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