Bioanode as a limiting factor to biocathode performance in microbial electrolysis cells

- In MECs hydrogen production from biocathode may be limited by bioanode.
- Electrogens enriched bioanode can maintain active at high applied potential up to 1.0 V.
- High demands of electrons on hydrogen production at cathode could exhaust bioanode.

The bioanode is important for a microbial electrolysis cell (MEC) and its robustness to maintain its catalytic activity affects the performance of the whole system. Bioanodes enriched at a potential of +0.2 V (vs. standard hydrogen electrode) were able to sustain their oxidation activity when the anode potential was varied from −0.3 up to +1.0 V. Chronoamperometric test revealed that the bioanode produced peak current density of 0.36 A/m2 and 0.37 A/m2 at applied potential 0 and +0.6 V, respectively. Meanwhile hydrogen production at the biocathode was proportional to the applied potential, in the range from −0.5 to −1.0 V. The highest production rate was 7.4 L H2/(m2 cathode area)/day at −1.0 V cathode potential. A limited current output at the bioanode could halt the biocathode capability to generate hydrogen. Therefore maximum applied potential that can be applied to the biocathode was calculated as −0.84 V without overloading the bioanode.

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