The inhibiting effect of oxygen diffusion on the electricity generation of three-chamber microbial fuel cells

摘要

Microbial fuel cell (MFC) as an emerging biotechnology is applied to generate electricity from the degradation of organic matter. This work explores the performance of the three-chamber MFCs in regard to oxygen diffusion with air aeration or radial oxygen swap (stream reaeration) cathodes during considerably prolonged operation (206 days). Results show that the oxygen diffusing from cathode chamber to anode chamber can accelerate the degradation of organic matter in anode chamber to some extent, and weaken the electricity generation of MFC. The electrogenesis for the radial oxygen swap cathode MFC (OSCMFC) is superior to air aeration cathode MFC (AACMFC), with the maximum voltage and power density of 0.855 V and 3.954 W m(-3), respectively. Compared with radial oxygen swap, air aeration causes more oxygen diffusion from cathode to anode chamber, which facilitates the growth of facultative anaerobes to accelerate the hydrolysis and acidification of the substrate and inhibits the activities of electricigens, resulting in the redox reaction of the oxygen and electrons in micro scales. The inhibiting effect of oxygen diffusion on electrogenic bacteria results in that a fraction of hydrolyzed organic matters is not converted into electricity, but rather to be devoured by non-electrogenic bacteria for the self-metabolic consumption and reproduction.