Browsing by Author "Freitag, Ruth"

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Comparative evaluation of the performance of a capacitive and a non-capacitive microbial fuel cell
(IEEE, 2021-03-25) Simeon, Meshack Imologie; A. L. Imoize; Freitag, Ruth
Electrode materials play a critical role in the performance of microbial fuel cells. This study investigates the contribution of capacitive bio-electrodes to sustainable power production in a single-chamber microbial fuel cell (MFC). The capacitive electrodes consisted of a stainless-steel wire mesh with an activated carbon layer, while the non-capacitive control electrodes were made of graphite felt with a wound current collector. The MFCs were constructed using a glass vessel with the anode completely buried in biologically active soil and the cathode placed above the soil to form a single-chamber configuration. The performance of the MFCs was investigated using linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). The results showed that the performance of the capacitive MFC was three times better than that of the non-capacitive MFC. While there was no significant difference in the Ohmic resistances of the MFCs, there was a significant difference in charge transfer resistance and capacitance of the MFCs. The capacitive MFC had a double layer capacitance of 8.282 µF in addition to the diffuse layer capacitance at the layer/metal interface of 2.012 F, while the non-capacitive MFC had a double layer capacitance of 5.034 µF with no diffuse layer capacitance. The results show that the capacitive characteristics of both cathode and anode improve the performance of a single-chamber MFC.
Electrochemical evaluation of different polymer binders for the production of carbon-modified stainless-steel electrodes for sustainable power generation using a soil microbial fuel cell.
(Chemical Engineering Journal Advances-Elsevier, 2022-01-11) Simeon, Meshack Imologie; Herkendell, Katharina; Pant, Deepak; Freitag, Ruth
In this study, four different polymeric binders - polytetrafluoroethylene (PTFE), two-component epoxy (epoxy), polyvinyl alcohol (PVA), and polyvinylidene fluoride (PVDF) - were used to fabricate a surface-modified stainless-steel electrode. The polymeric binders were used to bond highly conductive carbon-black to a stainless-steel support using a simple fabrication method. The electrodes' performance in sustainable power generation was tested in a soil microbial fuel cell (SMFC). PTFE showed the fastest and best initial response in no-load operation, reaching a voltage of 370 mV after 7 days, compared to epoxy, PVA, and PVDF, which had 163, 151.7, and -26.7 mV, respectively. Electrochemical measurements showed that epoxy and PVDF have similar redox potentials when operated as anode and cathode in an SMFC. Evaluation of the long-term performance of the binders showed that epoxy gave 2.2-, 3.4-, and 4.9-fold higher performance than PVDF, PTFE, and PVA, respectively, under intermittent polarization. Although PVDF did not perform well in open circuits, it produced the highest current density in continuous operation with external loads. The most sustained performance was obtained with epoxy. This study has shown that epoxy can be a suitable and eco-friendly substitute for other binders using a simple fabrication method to produce high-performance anodes and cathodes for sustainable bioelectricity generation with a SMFC.
Evaluation of the Electrical Performance of a Soil-Type Microbial Fuel Cell Treated with a Substrate at Different Electrode Spacings
(Proceedings of ICEESEN2020, 2020-11-21) Simeon, Meshack Imologie; Imoize, Agbotiname L.; Freitag, Ruth
The effect of electrode spacing on the performance of a microbial fuel cell (MFC) under batch treatment with a substrate was investigated with three single-chamber MFCs built with biologically active soil. The electrodes consisted of a stainless-steel mesh with layers of activated carbon catalyst. The MFCs were fed with artificial urine after reaching a stationary phase. After the initial treatment, the cell with the smallest electrode gap produced the maximum peak power under polarization. At 2 cm, 5 cm and 8 cm electrode spacing, the maximum power was 726.2 µW, 547 µW, and 520.3, respectively; while the average power of the MFCs from the first point of treatment with substrate to the last point was 297 + 259.2, 505.43+ 42.5, and 433.81+ 64, respectively. A significant decrease in internal resistance of the MFCs was observed during batch treatment. The impedance analysis of the MFCs showed that the reduction in internal resistance was largely due to a significant decrease in ohmic resistance compared to the charge transfer resistance.
Influence of electrode spacing and fed-batch operation on the maximum performance trend of a soil microbial fuel cell
(International journal o f hydrogen energy-Elsevier, 2021-12-04) Simeon, Meshack Imologie; Freitag, Ruth
The effect of electrode spacing on a soil microbial fuel cell (MFC) performance under fed-batch treatment with synthetic urine medium (SUM) was investigated at 2, 5, and 8 cm electrode spacing. The electrodes consisted of stainless-steel mesh with coarse layers of carbon-black. The MFCs were fed with SUM when the natural substrate of the medium was exhausted. Initial feeding resulted in 79.6, 108.7, and 103.1% increase in OCV with a proportional percentage increase in power at 2, 5, and 8 cm electrode spacing. Six days after the first feeding, the power was 189.9, 150.7, and 108. 5 mW/m2 in ascending order of electrode spacing. With more extended treatment, the overall maximum power was obtained at 8 cm spacing. In ascending order of electrode spacing, the highest power (207.92, 263.38, and 271.1 mW/m2) was obtained on days 39, 42, and 93, respectively. The study shows that a larger anode-to-cathode distance requires a longer time for the soil MFC to achieve stable and maximum performance in fed-batch operation.
Influence of Electrodes Spacing on the Maximum Power of a Soil Microbial Fuel Cell Based on Stainless-Steel-Nanocarbon Composite Electrodes.
(ISMET, 2021-10-09) Simeon, Meshack Imologie; Freitag, Ruth
The electrical output of microbial fuel cells (MFCs) is unstable due to the natural activities of the electroactive bacteria involved. To sustain the maximum performance of MFCs, an optimization of the architectural aspect is necessary with special consideration of electrode materials, electrode spacing, and substrate availability. This study was conducted with three single-chamber soil MFCs having different electrode spacings (2, 5 and 8 cm) and electrodes made of stainless-steel mesh with activated carbon catalyst layers to investigate the influence of the electrode spacings on the sustainability of the Maximum Power Point (MPP) of a soil MFC with synthetic urine medium (SUM) as substrate. The MFCs using mud from active soil were polarized every three days until the MPP was reached and then refueled with SUM every 6 days during a 90-day operating period. During the initial treatments, the maximum power was inversely proportional to the anode-cathode distance. However, this trend could not be maintained during continuous treatments, as the optimum performance was achieved with an electrode spacing of 5 cm. At 2 cm, 5 cm, and 8 cm electrode spacing, the maximum power and the open-circuit voltage were 695.67 + 36.0041 µW and 779.71 ±13.698 mV for 18 days, 517.66 ± 30.4 µW and 804.8 ±12.01 mV for 66 days, and 474.9 ± 45.3 µW and 757.49 ±11.488 mV for 54 days, respectively. During continuous treatment, the internal resistances of the MFCs decreased by 34.30, 28.2, and 41.87 %, respectively, due to an increase in electrolyte conductivity. Electrochemical impedance spectroscopy of the MFCs showed that the treatment had a more significant effect on electrolyte resistance than charge transfer resistance. These results showed that optimal cathode-anode spacing ensures substrate availability at the electrodes to maintain bacterial metabolism, resulting in stable performance of an MFC over a reasonably long period.
Optimization of soil microbial fuel cell for sustainable bio-electricity production: Combined effects of electrode material, electrode spacing and substrate feeding frequency on power generation and microbial community diversity
(Biotechnology for Biofuels and Bioproducts-BMC, 2022-11-16) Simeon, Meshack Imologie; Weig, A; Freitag, Ruth
Optimization of soil microbial fuel cell: influence of feeding duration, electrode factors and diversity factor of uncontrolled mixed microbial communities
(international Society for microbial Electrochemistry amd Technology-ISMET8, 2022-09-19) Simeon, Meshack Imologie; Freitag, Ruth
The electrochemical performance of the microbial fuel cell (MFC) depends not only on the operational and design parameters, but also on biological factors (Gadkari et al., 2019). Therefore, optimization studies that incorporate the interactive effects of the main influencing factors and the contributions of the biological factor would improve the understanding of the improvement strategies needed to advance the application of MFCs in the real world. While single-factor experiments are simple and less expensive to conduct, the reproducibility of the results of such experiments cannot be established with a high degree of confidence, especially in a complex system such as MFC. In this study, the feeding duration (4, 6 and 8 days), electrode material (carbon felt (CF) and modified stainless steel mesh (SM)), and electrode spacing (2, 4 and 8 cm) were integrated into a single design to optimize the performance of Soil MFC for stable and useful bioelectricity. The binder component of the SM was further optimized with four polymeric binders (epoxy, PVA, PVDF, and PTFE) and a new method - pasting and reinforcement (Simeon et al., 2022). PCR amplification and sequencing of 16S rDNA fragments were performed on the genomic DNA extracted from the MFCs, and bioinformatics analysis was performed using the QIIME2 microbiome analysis package. The results showed that the SM with a surface modified by conductive carbon black and epoxy binder exhibited superior performance in all experimental phases and achieved a maximum power three times higher than the CF at an electrode spacing of 4 cm and a feeding duration of 8 days. PVDF produced the highest current under real-time external loading, while epoxy produced the highest and most sustained power of 487.15 + 9.5 mW/m2 under linear polarization. Bioinformatic analysis revealed a wide bacterial diversity, with the most abundant phyla belonging to Proteobacteria (30-35%), Acidobacteriota (10-13%), Actinobacteriota (4-14%), Chloroflexi (6-9 %), Bacteroidota (3-9%), firmicutes (3-6%). Complex diversity in composition and abundance was observed mainly between the anode and cathode and between sampling time points, but no statistically significant difference was observed between the two electrode materials. This study indicates that the electrode material has the greatest influence on the sustainability and extent of bioelectricity capacity of a soil microbial fuel cell. Therefore, an increased focus on improving the electrode material would be a step in the right direction to position SMFCs as viable energy systems that can compete with the other established bio-electrochemical systems
Polarization and power density trends of a soil-based microbial fuel cell treated with human urine
(2020-03-14) Simeon, Meshack Imologie; Asoiro FU; Aliyu, M; Raji, OA; Freitag, Ruth
Microbial fuel cells (MFCs) are bio-electrochemical devices that use microbial metabolic processes to convert organic substances into electricity with high efficiency. In this study, the performance of a soil-based MFC using urine as a substrate was assessed using polarization and power density curves. A single-chamber, membrane-less MFC with a carbon-felt air cathode and a carbon-felt anode fully buried in biologically active soil was constructed to examine the impact of urine treatment on the performance of the MFC. The peak power of the urine-treated MFC was 124.16 mW/m2 and was obtained 24 hours after the first urine addition; a control MFC showed a value of 65.40 mW/m2 in the same period. The treated MFC produced an average power of 70.75 mW/m2 up to 21 days after the initial urine addition; the control MFC gave an average value of 4.508 mW/m2 over the same period. The average internal resistances of the treated MFC and the control MFC obtained after the initial treatment were 269.94 and 1627.89 Ω, respectively. This study demonstrates the potential of human urine to reduce internal losses in soil MFCs and to provide stable power densities across various external resistors. These results are propitious for future advancements in soil MFCs for power generation, utilizing human urine (a readily available source of nutrients) as a substrate.
The applicability of the Maximum Power-point of Microbial Fuel Cells: Influence of Potential Scan rate and real-time external Load
(international Society for microbial Electrochemistry amd Technology-ISMET, 2021-09-15) Simeon, Meshack Imologie; Freitag, Ruth
Performance evaluation of a microbial fuel cell (MFC) is usually done with linear sweep voltammetry (LSV) [1] at a given potential scan rate (PSR) [2]. This evaluation does not often reflect the long-term performance of the MFC under real-time external loads [1]. In this study, the performance of a single-chamber MFC was evaluated with three external loads (1206, 470, and 270 Ohms) calculated from LSV maximum power point (MPP) with three PSRs (0.1, 0.5, and 1 mV/s). The estimated power from the MPP in ascending order of PSR was 61.96, 87.88, and 166.68 mW/m2 at 116.5, 229.6, and 403 mA/m2, respectively. The average power obtained with 1206, 470, and 270 Ohms in the first two hours of operation was 73 + 16.7, 36.3 + 42, and 88.5 + 120.1 mW/m2 at current densities of 124.6 + 14.3, 121.2 + 73.4, and 232.6 + 176.2 mA/m2, respectively. The result showed that overestimation was more pronounced at higher PSRs. Although the MFC was initially underestimated at 0.1 mV/s, this PSR more accurately reflects the true and applicable estimate of the long-term performance of the MF vC. These results are explicitly beneficial for ethe lectrochemical estimation of the actual performance of MFCs under real-time external loads