Characterization of anode and anolyte community growth and the impact of impedance in a microbial fuel cell

Abstract

BackgroundA laboratory-scale two-chamber microbial fuel cell employing an aerated cathode with no catalyst was inoculated with mixed inoculum and acetate as the carbon source.Electrochemical impedance spectroscopy (EIS) was used to study the behavior of the MFC during initial biofilm (week 1) and maximum power density (week 20). EIS were performed on the anode chamber, biofilm (without anolyte) and anolyte (without biofilm). Nyquist plots of the EIS data were fitted with two equivalent electrical circuits to estimate the contributions of intrinsic resistances to the overall internal MFC impedance at weeks 1 and 20, respectively.ResultsThe results showed that the system tended to increase power density from 15 ± 3 (week 1) to 100 ± 15 mW/m2 (week 20) and current density 211 ± 7 (week 1) to 347 ± 29 mA/m2 (week 20). The Samples were identified by pyrosequencing of the 16S rRNA gene and showed that initial inoculum (week 1) was constituted by Proteobacteria (40%), Bacteroidetes (22%) and Firmicutes (18%). At week 20, Proteobacterial species were predominant (60%) for electricity generation in the anode biofilm, being 51% Rhodopseudomonas palustris. Meanwhile on anolyte, Firmicutes phylum was predominant with Bacillus sp.This study proved that under the experimental conditions used there is an important contribution from the interaction of the biofilm and the anolyte on cell performance. Table 1 presents a summary of the specific influence of each element of the system under study.ConclusionsThe results showed certain members of the bacterial electrode community increased in relative abundance from the initial inoculum. For example, Proteobacterial species are important for electricity generation in the anode biofilms and Firmicutes phylum was predominant on anolyte to transfer electron.R1 is the same in the three systems and no variation is observed over time.The biofilm makes a significant contribution to the charge transfer processes at the electrode (R2 and Cdl) and, consequently, on the performance of the anode chamber.The biofilm can act as a barrier which reduces diffusion of the anolyte towards the electrode, all the while behaving like a porous material.The anolyte and its interaction with the biofilm exert a considerable influence on diffusion processes, given that it presents the highest values for Rd which increased at week 20.

Evolving Microbial Communities in Cellulose-Fed Microbial Fuel Cell

“…The main phylum that was enriched on the anode after 30 days of stable operation in MFC was Bacteroidetes, which increased from 0.8% in the inoculum to 34% in the MFC (Figure 3). Bacteroidetes have previously been reported to dominate the anode consortium of a two-chamber MFC fed wheat straw hydrolysate, and were also found in two-chamber acetate-fed MFCs [16,32] as well as in a single-chamber MFC [33]. The most abundant phylum was Firmicutes, with 32% in the inoculum and 50% after 30 days.…”

Electrochemical and impedance characterization of Microbial Fuel Cells based on 2D and 3D anodic electrodes working with seawater microorganisms under continuous operation

“…Indeed, polarization curves are generally used to measure the open circuit voltage (OCV) and to estimate both the maximum current density and the maximum power output of the MFCs (Clauwaert et al, 2008). Instead, EIS is a powerful AC technique widely employed in different fields of electrochemistry (Barsoukov & Macdonald, 2005;Hernández et al, 2014;Hernández et al, 2015), including MFC systems (Dominguez-Benetton et al, 2012;Martin et al, 2013;Sanchez-Herrera et al, 2014), which results highly useful when the different resistances values for each process involved in the MFC operation cannot be easily determined from a polarization curve. EIS is considered as an accurate technique for analyzing bio-electrochemical reactions on electrodes, internal resistances, biofilm development and immobilization on the different materials, estimating electrode properties, and studying the mass transfer resistances due to the diffusion limitations of the reactants (Dominguez-Benetton et al, 2012;He & Mansfeld, 2009;Manohar et al, 2008).…”

Performance of a greywater cathode in a microbial fuel cell with three ion exchange membranes

“…This is due to differences in anode biofilm. It has been reported that microbial growth has a beneficial effect on anode biolectrochemical kinetics, causing changes in charge transfer resistance, as a previous work observed that charge transfer resistance decreased from 7427 to 55.73 Ω between 1 and 20 weeks, which was attributed to anode microbial density increase …”

“…It has been reported that microbial growth has a beneficial effect on anode biolectrochemical kinetics, causing changes in charge transfer resistance, as a previous work observed that charge transfer resistance decreased from 7427 to 55.73 Ω between 1 and 20 weeks, which was attributed to anode microbial density increase. 81 The coefficient of constant phase element > 0.80, as was the case with the Nafion ® stack, AMI-7001 stack and CMI-7000 stack, suggests a pseudocapacitive process in the anode electrode. It has been demonstrated through impedance measurements that the carbon veil and anode biofilm, in an MFC, are capable of storing energy, obtaining coefficient values up to 0.89 and 0.78 for carbon veil and biofilm, respectively, 82 demonstrating that carbonaceous materials such as biofilm have pseudocapacitive behavior.…”