Performance improvement of microbial fuel cells by fermentation gas driven fluidization of magnetite nanoparticles and carbon particles

Abstract

In this study, a multiphase flow model using fermentation gas-driven magnetite nanoparticles and carbon particles in the anode chamber is proposed to improve the power generation performance. The fluidized carbon particles attached by electroactive biofilms are used as dynamic electrodes. Free electrons are transferred from the electrolyte to the electrode via the fluidized magnetite nanoparticles acting as the electron shuttle medium, and electron conduction in the biofilm thickness direction is assisted by the magnetite nanoparticles fixed within the biofilm, both of which together construct the conductive grids from the carbon particles to the electrode. The power density of 0.36 mW/cm2 and the surprising open-circuit voltage of 0.98 V are obtained. Microbial morphology of the model with carbon particles and magnetite nanoparticles shows a higher bacterial density of biofilms and stronger Fe response on the cell membrane surface than the model with carbon particles, also the interspecific electron transfer channels between bacteria are established by magnetite nanoparticles. Further tests indicate that the improved electricity generation performance of the carbon particles and magnetite nanoparticles model with fluidized states can be attributed to their excellent capacitive properties, lower electron transfer resistance, and enrichment of electroactive bacteria by magnetite.