Self-stratifying microbial fuel cell: The importance of the cathode electrode immersion height

Power generation of bioelectrochemical systems (BESs) is a very important electrochemical parameter to consider particularly when the output has to be harvested for practical applications. This work studies the effect of cathode immersion on the performance of a self-stratified membraneless microbial fuel cell (SSM-MFC) fuelled with human urine. Four different electrolyte immersion heights, i.e. 14, 24, 34 and fully submerged were considered. The SSM-MFC performance improved with increased immersion up to 34. The output dropped drastically when the cathode was fully submerged with the conditions becoming fully anaerobic. SSM-MFC with 34 submerged cathode had a maximum power output of 3.0 mW followed by 2.4 mW, 2.0 mW, and 0.2 mW for the 24, 14 and fully submerged conditions. Durability tests were run on the best performing SSM-MFC with 34 cathode immersed and showed an additional increase in the electrochemical output by 17% from 3.0 mW to 3.5 mW. The analysis performed on the anode and cathode separately demonstrated the stability in the cathode behaviour and in parallel an improvement in the anodic performance during one month of investigation.