Parallel Connection and Sandwich Electrodes Lower the Internal Resistance in a Microbial Fuel Cell

Abstract

The aim of this work was to design and characterize a novel, multiface parallelepiped MFC in the perspective of decreasing the internal resistance (Rint) and increasing the volumetric power (Pv) output. The cell was fitted with a ‘sandwich’ cathode-membrane-anode assemblage in five of its faces, and possessed a ratio electrode surface area-to-volume ξ (csi) of 19 m-1 .
 When the 5 faces of the MFC-P were connected in series, the Rint was 601 Ω with a voltage of 0.52 V. Characterization of the cell with the 5 faces connected in parallel gave a Rint of 62 Ω with a voltage of 0.5 V that corresponded to external resistance of 56 k Ω in the polarization procedure. This result was ascribed to both the changes in cell architecture and decrease of the inter-electrode distance as well as the parallel connection. The Pv of the new MFC-P achieved values of 62 and 570 mW/m3 for series and parallel connection, respectively.
 Molecular ecological techniques were used to analyze the bacterial diversity of biocatalyst used in new design MFC-P. They showed a low species richness and low-to-moderate evenness. The community consisted primarily of δ-Proteobacteria and Firmicutes, bacteria that are recognized to be capable of exocellular electron transfer.

Assessing the impact of design factors on the performance of two miniature microbial fuel cells

“…The lowest internal resistance was in fact achieved with the stack of two cascades (eight devices), with values of 0.5 kΩ (MFCConf.1) and 2.9 kΩ (MFCConf.2). These results, in agreement with previous studies, is associated with an enhanced ion flow due to the functional increase in the anodic area achieved with stacking (Ortega-Martínez et al, 2012;Wang & Han, 2009). When MFC units are electrically connected in parallel the internal resistance tends to the lowest (Papaharalabos et al, 2015).…”

“…This connection strategy, however, can produce a voltage reversal phenomenon that can damage MFC units in the stack (An et al, 2016;Ortega-Martínez et al, 2012;Wang & Han, 2009). The connection in parallel results in an overall current equal to the sum of the current generated by the individual MFC, while the voltage is constant.…”

“…The connection in parallel results in an overall current equal to the sum of the current generated by the individual MFC, while the voltage is constant. An electrical connection in parallel decreases the internal resistance and is therefore preferred (Ortega-Martínez et al, 2012). Nonetheless, when higher voltages are required, a combination of both parallel and series electrical connection has been proposed to avoid the use of a low voltage electronic controller to harvest energy and store power in a re-chargeable battery or super-capacitor, which would reduce overall efficiency (Gajda et al, 2018).…”