Mathematical modeling and performance evaluation of a cathodic bi-population microfluidic microbial fuel cell

Microfluidic microbial fuel cell, as a novel achievement of miniature microbial fuel cell, can be used in various fields such as poison detection, biosensors, etc. To investigate the mass transport and bacterial distribution inside the microfluidic microbial fuel cell, an innovative two-dimensional numerical model of microfluidic microbial fuel cell is proposed in this paper. This model is built via finite element method and the growth of bi-population microorganisms (exoelectrogens and facultative anaerobic bacteria) are coupled into the bioelectrochemical reaction kinetics. The accuracy of the present model is ensured by comparing the simulation results with other studies. After that, the effects of pH, dissolved oxygen and electrode porosity on the cell performance and spatial distribution of microorganisms are explored. Conclusions indicate that the pH gradient caused by the accumulation of hydrogen ions and hydroxide ions inhibits the growth of bacteria and mainly affects the anode performance. Higher electrode porosity enhances substrate transport and facilitates microbial growth. However, the effective conductivity of porous electrodes decreases with increasing porosity, which increases ohmic loss. Therefore, MMFC achieves an optimal power density of 956 W m−3 at a porosity of 0.6. Higher dissolved oxygen concentration contributes to enhancing the performance of microfluidic microbial fuel cell. The proposed model can provide strategies for the optimal design of microfluidic microbial fuel cell.