Anodic potential on dual-chambered microbial fuel cell with sulphate reducing bacteria biofilm

Dual chamber microbial fuel cell reactors were inoculated with a mixed culture of sulfate-reducing bacteria with anode potential being the controlling parameter. A negative poised anode potential enhanced the performance of this fuel cell while a positive poised anode potential had adverse effects on cell performance. Negative anodic potential affects the biofilm characteristics, as evidenced by electrochemical analysis. Microbial community was changed accordingly.     

The production of electricity from dual-chambered microbial fuel cell fueled by old age leachate

In this study, electricity production from old age landfill leachate was investigated using dual chambered microbial fuel cell with Ti-TiO₂ electrodes. The effect of organic loading rate on microbial fuel cell performance was examined by changing the hydraulic retention time and leachate chemical oxygen demand (COD) concentration. Microbial diversity at different conditions was studied using PCR-DGGE profiling of 16 sRNA fragments of microorganisms in the liquid media of the anode chamber and of the biofilm on the anode electrode. Both COD removal and current density were positively affected with increasing organic loading rate. The highest microbial fuel cell performance was achieved at hydraulic retention time of 0.5 day and organic loading rate of 10 g COD/L.day. The performance of the microbial fuel cell reactor decreased when hydraulic retention time was reduced to 0.25 day. The investigation of the microbial dynamics indicated that abundance of bacterial species was considerably dependent on the operational conditions. The microbial fuel cell reactor was mainly dominated by Geobacter, Shewanella, and Clostridium species, and some bacteria were easily washed out at lower hydraulic retention times.     

Modeling the performance of molten carbonate based direct carbon fuel cell anode

A mathematical model is developed to study the performance of a molten carbonate based direct carbon fuel cell anode. The direct carbon fuel cell(DCFC) is a fuel cell which uses solid carbon as fuel and molten carbonate as electrolyte. The model assumes that the 4 electron carbon oxidation reaction is the primary reaction driving the DCFC. However, the 2 electron CO oxidation reaction and the reverse Boudouard reaction is also considered in this model. The model studies the effect of performance parameters on the performance of the DCFC. The effect of the bulk conductivity in the solid phase, the bulk conductivity in the liquid phase, carbon loading and the thickness of the anode layer on the potential and current distribution in the cell is modeled. Model results are compared with experimental data and found to compare well.     

The effect of nitric acid,ethylenediamine, and diethanolamine modified polyaniline nanoparticles anode electrode in a microbial fuel cell

Anode materials are important in the power generation of microbial fuel cell. In this study, polyaniline was used as a conducting polymer anode in two chambers MFC. XPS and SEM were used for the characterization of functional groups of anode materials and the morphology. The power generation of microbial fuel cell was elevated by the modification of anode by nitric acid, ethylenediamine, and diethanolamine. The time that MFC reaches its maximum power generation was shortened by modification. Moreover the SEM photos prove that, it causes better attachment of microorganisms as biocatalysts on electrode surface. The best performance of among the MFCs with different anode electrodes, was the system working by polyaniline modified by ethylenediamine as that generated power of 136.2 mW/m² with a 21.3% Coulombic efficiency.     

Investigating the effect of membrane layers on the cathode potential of air-cathode microbial fuel cells

This study investigates the effect of cation exchange membrane (CEM) diffusion layers on cathode potential behavior in microbial fuel cells based on a cobalt electrodeposited anode that works in actual industrial wastewater. The structural properties of the modified anode materials were evaluated using scanning electron microscopy (SEM), which showed a strong and clear biofilm layer on the anode surface. Additionally, the structural properties of the utilized cathode materials were evaluated using energy dispersive X-ray (EDX) spectrometry and field emission scanning electron microscopy (FE-SEM) techniques, which confirmed the transfer of cobalt ions through the CEM to the cathode surface. Finally, the performance of the modified anode material with various CEMs as diffusion layers was investigated in air-cathode microbial fuel cells. The results indicate that the metal electrodeposition strategy, which utilizes multiple CEM layers, enhanced the power and current generation by 498.2 and 455%, respectively. Moreover, the Columbic efficiency (CE) increased by 77%, 154.5%, and 232% for the MFC with one, two and three CEM layers, respectively.     

Ti4O7 supported IrOx for anode reversal tolerance in proton exchange membrane fuel cell

Fuel starvation can occur and cause damage to the cell when proton exchange membrane fuel cells operate under complex working conditions. In this case, carbon corrosion occurs. Oxygen evolution reaction (OER) catalysts can alleviate carbon corrosion by introducing water electrolysis at a lower potential at the anode in fuel shortage. The mixture of hydrogen oxidation reaction (HOR) and unsupported OER catalyst not only reduces the electrolysis efficiency, but also influences the initial performance of the fuel cell. Herein, Ti₄O₇ supported IrO_x is synthesized by utilizing the surfactant-assistant method and serves as reversal tolerant components in the anode. When the cell reverse time is less than 100 min, the cell voltage of the MEA added with IrO_x/Ti₄O₇ has almost no attenuation. Besides, the MEA has a longer reversal time (530 min) than IrO_x (75 min), showing an excellent reversal tolerance. The results of electron microscopy spectroscopy show that IrO_x particles have a good dispersity on the surface of Ti₄O₇ and IrO_x/Ti₄O₇ particles are uniformly dispersed on the anode catalytic layer. After the stability test, the Ti₄O₇ support has little decay, demonstrating a high electrochemical stability. IrO_x/Ti₄O₇ with a high dispersity has a great potential to the application on the reversal tolerance anode of the fuel cell.     

Effect of anode conditions on the performance of direct borohydride–hydrogen peroxide fuel cell system

Direct borohydride–hydrogen peroxide fuel cells (DBHPFCs) are attractive power sources for space applications. Although the cathode conditions are known to affect the system performance, the effect of the anode conditions is rarely investigated. Thus, in this study, a DBHPFC system was tested under various anode conditions, such as electrocatalyst, fuel concentration, and stabilizer concentration, to investigate their effects on the system performance. A virtual DBHPFC system was analyzed based on the experimental data obtained from fuel cell tests. The anode electrocatalyst had a considerable effect on the mass and electrochemical reaction rate of the fuel cell system, but had minimal effect on the decomposition reaction rate. The NaBH₄ concentration greatly influenced the mass and decomposition reaction rate of the fuel cell system; however, it had minimal impact on the electrochemical reaction rate. The NaOH concentration affected the electrochemical reaction rate, decomposition reaction rate, and mass of the fuel cell system. Therefore, the significant effects of the anode conditions on the electrochemical reaction rate, decomposition reaction rate, and mass of the fuel cell system prompt the need for their careful selection through fuel cell tests and system analysis.     

Enhanced performance of sediment microbial fuel cell by immobilization of Shewanella oneidensis MR-1 on an anode surface

The anodic microbial community especially relative abundance of exoelectrogens is crucial for performance enhancement of sediment microbial fuel cell (SMFC). In this study, Shewanella oneidensis MR-1 was immobilized on an active carbon fiber anode and the SMFC's performance was evaluated. The maximum power density of SMFC with immobilized strain MR-1 (SMFC-ImSW) displayed 61.0 mW/m², and SMFC with conventional bioaugmentation (SMFC-SW) and no treatment (SMFC-CK) of strain MR-1 obtained 11.1 and 2.4 mW/m², respectively. The chemical oxygen demand removal efficiency of SMFC-ImSW was 14.2% and 24.2% higher than SMFC-SW and SMFC-CK groups, respectively. Furthermore, the organics removal efficiencies of sediment were also increased in SMFC-Imsw. GFP-tagging and RT-PCR results showed that strain MR-1 was colonized on the anode biofilm of SMFC-ImSW. Cyclic voltammetry and Electrochemical impedance spectroscopy results showed that higher redox potential and charge transfer efficiency presented with immobilized strain MR-1. MiSeq sequencing results showed that Sphaerochaetaceae and Marinilabiaceae were also enriched on the anode biofilm, which are related to power generation. These results demonstrated that immobilized bioaugmentation is an ideal approach to improve SMFC performance.     

Effect of an anode modified with nitrogenous compounds on the performance of a microbial fuel cell

Three kinds of nitrogenous compounds (ammonium peroxydisulfate, ethylenediamine, methylene blue) were applied to modify graphite felt anodes in microbial fuel cells. All of the performances were greatly improved by modifying the anode surface. The maximum power density of the microbial fuel cell with modified anode was 355, 545, and 510 mW/m², respectively, which was larger than the ungroomed control (283 mW/m²). The power density of microbial fuel cell with ethylenediamine-treated electrode was highest among the four microbial fuel cells. The increase of power density was correlated with the changes of N/C and O/C ratios on the anode according to the X-ray photoelectron spectrometry analysis.     

Different flow fields,operation modes and designs for proton exchange membrane fuel cells with dead-ended anode

Water and nitrogen can accumulate in the anode channel in proton exchange membrane fuel cells (PEMFCs) with dead-ended anode (DEA) and can affect cell performance significantly. In this paper, the cell performance characteristics in DEA PEMFCs with three different anode flow fields under two operating modes are studied through measuring the cell voltages and local current densities. The effect of the anode exit reservoir is also studied for the three different anode flow fields. The experimental results show that the interdigitated flow field has the most stable cell performance under both constant pressure and pressure swing supply modes. Parallel and serpentine flow fields lead to very non-uniform local current distributions under constant pressure supply mode and experience severe fluctuations and spikes in local current densities under pressure swing supply mode. The results also show that anode pressure swing supply mode can achieve more stable cell performance than anode constant pressure supply mode for parallel and serpentine anode flow fields. The anode exit reservoir can significantly improve cell performance stability for parallel and serpentine flow fields, but has no significant effect on interdigitated flow fields. Besides, the results further show that PEMFCs with DEA can maintain very stable operation with anode serpentine flow field and an anode exit reservoir under pressure swing operation.     

Insight into graphite oxidation in a NiO-based hybrid direct carbon fuel cell

A direct carbon fuel cell is an electricity generation device using solid carbon as a fuel directly with no reforming process. In this study, three-carbon fuels, graphitic carbon (GC), carbon black (CB), and biomass carbon (BC) are tested as the fuel to investigate the influence of carbon fuel properties on the cell performance in HDCFC with a traditional nickel oxide as the anode. Either an electrolyte-supported cell with a thin nickel oxide anode or an anode-supported cell with a thick nickel oxide anode is used to evaluate the electrochemical reactivity of carbon samples. These three-carbon fuels are characterised on the crystal structure, particle size, composition, and surface property. It is found that GC shows excellent cell performance on thin nickel oxide anode. However, it displays relatively slow electrochemical reactivity on the thick anode due to its great extent of carbon oxidation. BC shows good initial cell performance but fast degradation of the cell performance, as much more hydrogen is released at the beginning of the cell test. The anode reactions of HDCFCs are explored by the in-situ gas analysis in open circuits and under current load conditions. It is observed that GC produces the highest amount of CO among these three fuels, suggesting that carbon oxidation is the dominant electrochemical process in HDCFCs after a certain time when most of the hydrogen is released from the pyrolysis process.     

Effect of surface modification of anode with surfactant on the performance of microbial fuel cell

Surface modification of anode using surfactant has great influence on the electrical performance of a microbial fuel cell (MFC). In this study, the effect of surface‐modified exfoliated graphite used for anode fabrication on a cube‐type MFC batch reactor was examined. The surface exfoliated graphite was modified with 5‐mM anionic surfactant, sodium dodecyl sulfate. Anaerobic sludge used as inoculum containing 70% (v/v) of artificial wastewater and 30% (v/v) of seed sludge in an anode chamber and air cathode was used in cathode side. Anode modification was explored as an approach to enhance the start‐up and improve the performance of the reactor. Scanning electron microscopy was used to evaluate the morphology and activity of electrochemically active bacteria. In the study, the start‐up time of MFC required to approach stable voltage was substantially reduced, and the maximum stable voltage was higher than the control. In addition, the activation resistance of the MFC was considerably reduced, and the maximum power density (1640 mW/m²) was 20% higher than control. However, when the surface of exfoliated graphite was modified with over 10‐mM anionic surfactant, some negative effects on start‐up time, activation resistance and maximum power density were observed. This modification also enhanced the bacterial attachment and biofilm formation on the modified anode surface. The result suggested that surface modification anode with surfactant is effective for electrical responses achieved in the MFC. Copyright © 2015 John Wiley & Sons, Ltd.     

A general electrolyte–electrode-assembly model for the performance characteristics of planar anode-supported solid oxide fuel cells

A general electrode–electrolyte-assembly (EEA) model has been developed, which is valid for different designs of solid oxide fuel cells (SOFCs) operating at different temperatures. In this study, it is applied to analyze the performance characteristics of planar anode-supported SOFCs. One of the novel features of the present model is its treatment of electrodes. An electrode in the present model is composed of two distinct layers referred to as the backing layer and the reaction zone layer. The other important feature of the present model is its flexibility in fuel, having taking into account the reforming and water–gas shift reactions in the anode. The coupled governing equations of species, charge and energy along with the constitutive equations in different layers of the cell are solved using finite volume method. The model can predict all forms of overpotentials and the predicted concentration overpotential is validated with measured data available in literature. It is found that in an anode-supported SOFC, the cathode overpotential is still the largest cell potential loss mechanism, followed by the anode overpotential at low current densities; however, the anode overpotential becomes dominant at high current densities. The cathode and electrolyte overpotentials are not negligible even though their thicknesses are negligible relative to the anode thickness. Even at low fuel utilizations, the anode concentration overpotential becomes significant when chemical reactions (reforming and water–gas shift) in the anode are not considered. A parametric study has also been carried out to examine the effect of various key operating and design parameters on the performance of an anode-supported planar SOFCs.     

Experimental factors that influence carbon monoxide tolerance of high-temperature proton-exchange membrane fuel cells

The poisoning effect of carbon monoxide (CO) on high-temperature proton-exchange membrane fuel cells (PEMFCs) is investigated with respect to CO concentration, operating temperature, fuel feed mode, and anode Pt loading. The loss in cell voltage when CO is added to pure hydrogen anode gas is a function of fuel utilization and anode Pt loading as well as obvious factors such as CO concentration, temperature and current density. The tolerance to CO can be varied significantly using a different experimental design of fuel utilization and anode Pt loading. A difference in cell performance with CO-containing hydrogen is observed when two cells with different flow channel geometries are used, although the two cells show similar cell performance with pure hydrogen. A different combination of fuel utilization, anode Pt loading and flow channel design can cause an order of magnitude difference in CO tolerance under identical experimental conditions of temperature and current density.     

Synergistic interaction of biocatalyst with bio-anode as a function of electrode materials

Comprehensive study was performed to understand the synergistic interaction between the biocatalyst and anode in terms of electron discharge (ED) pattern and microbial growth by varying electrode (bio-anode) materials viz., graphite, aluminum, brass, copper, nickel and stainless steel. Experiments were performed in bio-electrochemical cell consisting of three electrodes (bio-anode as working electrode, carbon rod as counter electrode and Ag/AgCl(S) as reference electrode) employing anaerobic mixed culture as anodic biocatalyst. Voltammetric and chronoamperometric analysis were used to enumerate the ED and redox reactions. Presence of higher microbial population and dominance of Gram positive bacteria with higher ED supported graphite function as a good bio-anode material. Nickel and stainless steel showed higher ED after graphite associated with dominance of Gram positive bacterial population. Although higher ED was noticed with brass, metal oxidation and decrement in ED with time doesn’t support its function as bio-anode. In spite of higher ED than nickel and stainless steel, aluminum and copper showed significant metal oxidation leading to change in both physical and electrochemical properties along with dominant growth of Gram negative bacteria. This study gives a comprehensive idea on biocatalyst interaction with anode in extracellular electron transfer which is important in improving the anode performance. Juxtaposing the results, it can be deduced that the outcome of the present study can be extended to all bio-electrochemical systems including microbial fuel cell (MFC).     

微生物燃料电池阳极材料研究进展

微生物燃料电池（microbial fuel cell,MFC）是一种新型的生物电化学装置,能将可生物降解有机物中的化学能直接转化成电能,而阳极材料性能是影响MFC性能的重要因素之一。通过对阳极材料进行改性和修饰可以有效地增大其比表面积、生物相容性等,以提高其微生物负载率和电子传递速率,进而提高MFC的产电性能。本文全面介绍和总结了近年来国内外关于微生物燃料电池阳极材料的研究进展,分析微生物燃料电池阳极材料在规模放大应用中存在的问题,并对微生物燃料电池阳极材料今后的发展方向进行了展望。     

Effect of iridium oxide as an additive on catalysts with different Pt contents in cell reversal conditions of polymer electrolyte membrane fuel cells

Cell reversal is observed when a current load is applied to the polymer electrolyte membrane fuel cell under fuel starvation conditions. Cell reversal causes severe corrosion (or oxidation) of the carbon support in the anode, which leads to a decrease in overall fuel cell performance. To suppress the corrosion reaction of carbon under cell reversal conditions and to increase the durability of fuel cells, studies on anode additives are being conducted. However, studies on the effect of additives on catalysts with different platinum contents have not been conducted. In this study, 20 wt%, 40 wt%, 60 wt% commercial Pt/C catalyst was applied to the anode, and 50 cycles of cell reversal were performed. Furthermore, the performance change with and without IrO₂ as an additive was observed and its effect was assessed. Changes in the morphologies of the electrodes before and after cell reversal tests were also observed using a transmission electron microscope and a scanning electron microscope. The higher the platinum content of the catalyst, the more resistant to cell reversal. In addition, the addition of IrO₂ to the anode effectively prevents performance degradation due to cell reversal.     

Composite‐modified anode by MnO2/polypyrrole in marine benthic microbial fuel cells and its electrochemical performance

Low power limits the application of microbial fuel cells (MFCs). Our research mainly focuses on the modification of the electrode and looking for new anode material for high‐power marine benthic microbial fuel cells(BMFCs). A MnO₂/PPy composite‐modified anode was fabricated by in situ chemical polymerization. Surface topography and properties were characterized by scanning electron microscopy and infrared spectroscopy, respectively, indicating that the MnO₂/PPy composite is of a ‘mosaic‐like’ microstructure. The electrochemical performance and wettability of different kinds of anode were investigated respectively. Cyclic voltammetry and linear sweep voltammetry tests show that MnO₂/PPy composite‐modified electrode has a typical capacitance feature; its capacitance is 3.1 times higher than that of unmodified electrode. Contact angle of the composite‐modified anode reduces to 46 ± 0.5°, and its kinetic activity increased for more than 1.1 times. The maximum output power density of MnO₂/PPy composite‐modified cell reached 562.7 ± 10 mW m^?2, which is 2.1‐fold of the unmodified one. Finally, the composite‐modified anode provides an alternative potential choice for high‐performance cell, and the possible influence mechanism of composite materials on the BMFCs was also analyzed. Copyright © 2016 John Wiley & Sons, Ltd.     

Bioelectricity production from municipal leachate in a microbial fuel cell: Effect of two cathodic catalysts

The objective of this work was to evaluate the effect of the cathodic catalyst (either chalcogenide or Pt) on bioelectricity production from actual municipal leachate in a microbial fuel cell equipped with an anode made of granular graphite (MFC-G) and seeded with an inoculum enriched in Mn(IV)-reducing bacteria.     

阳极材料对微生物燃料电池性能影响的研究

以石墨、碳纸、碳布和碳毡为阳极材料,研究不同材料在微生物燃料电池中的产电性能,并利用循环伏安法比较不同材料的电化学活性。结果表明:在电池性能方面,以石墨为阳极微生物燃料电池电压可达0.678V,输出功率为250mW/m2;碳毡电压达0.656V,输出功率204mW/m2,碳纸0.649V,输出功率156mW/m2;碳布最差,电压不稳定,输出功率56mW/m2。循环伏安曲线和电极材料表观吸附量:碳毡作为阳极材料,具有明显的氧化峰和还原峰,对导电微生物具有显著的吸附量,其次是石墨,碳纸次之,最差的是碳布。