Anode Of Microbial Fuel Cell Research Articles

Interplay of Anode, Cathode, and Current in Microbial Fuel Cells: Implications for Wastewater Treatment

AbstractThe anode and cathode potentials determine the overall performance of a microbial fuel cell (MFC). Thus far, research has focused on understanding the performance of individual electrodes, but there has been no investigation of how the anode or cathode potential changes as a function of the other. This study demonstrates for the first time that interplay exists between the anode and cathode electrodes, a phenomenon whereby reduction of voltage losses at one electrode increases voltage losses at the other. With our experimental data and results from the literature, a model was developed to quantify the interplay at theoretical and applied levels for wastewater treatment. The cause of the interplay was attributed to the reactant/product concentration gradient that exists between the bulk‐catholyte–cathode and biofilm–anode electrode surfaces. These findings advance our fundamental understanding of MFCs and provide new insight into how to improve performance for wastewater treatment and energy production.

Production of low or non-alcoholic beer in microbial fuel cell

Microbial fuel cells (MFC) are bioreactors that are used to generate electricity on the expense of organic substrate oxidation. The MFC's operation-mechanism offers the possibility to use the fuel cell in the beer production technologies to make low or non-alcoholic beers. In this study the effect of MFC anode surface area and riboflavin as an electron shuttle on electric current and on ethanol production in fermentation of wort is demonstrated. The enlargement of anode surface induces an increase of electricity generation (from 4 to 12.5mA/m2) while the ethanol production decreases. Adding riboflavin to the wort in the MFC results significant increase in electricity production, furthermore it decreases the ethanol synthesis. Addition of 50μM riboflavin enhances the current output to 51mA/m2 with a 1.5V/V% decrease of ethanol production, while 100μM results 86mA/m2 and 2V/V% decrease of ethanol production. These results show the potentiality to brew low or non-alcoholic beer in MFC.

Architectural design of hierarchically meso–macroporous carbon for microbial fuel cell anodes

The HN-C exhibited a high power density (1034 mW m−2), which was much higher than the macroporous carbon anode MFC (811 mW m−2) and mesoporous carbon anode MFC (678 mW m−2) and was 2.2-folds that of carbon cloth anode MFC (467 mW m−2).

Titanium dioxide nanoparticles modified three dimensional ordered macroporous carbon for improved energy output in microbial fuel cells

Pore structure and surface biocompatibility are crucial factors for microbial fuel cell (MFC) anode performance. In this study, we demonstrated a templating strategy for design of three dimensional ordered porous carbon (3DOM-C) well-patterned macrospores (ca, 400nm) decorated carbon cloth as anode for high power density MFC. Titanium dioxide nanoparticles (TiO2) were synthesized to modify the 3DOM-C for increasing biocompatibility. The results of SEM, X-ray diffraction, and nitrogen adsorption-desorption studies demonstrated the hybrid composite had a honeycomb structure with uniform macroporous distribution and high specific surface area. In comparison with carbon cloth MFCs, the hybrid TiO2/3DOM-C anode delivered 2.3-fold higher power density of 973mWm−2. The increased energy output was contributed to synergetic effects between TiO2 and 3DOM-C due to their unique properties leading to significantly improved electrocatalysis.

Self-powered supercapacitive microbial fuel cell: The ultimate way of boosting and harvesting power

In this work, for the first time, we demonstrate a supercapacitive microbial fuel cell which integrates the energy harvesting function of a microbial fuel cell (MFC) with the high-power operation of an internal supercapacitor. The pursued strategies are: (i) the increase of the cell voltage by the use of high potential cathodes like bilirubin oxidase (BOx) or iron–aminoantipyrine (Fe–AAPyr); (ii) the use of an additional capacitive electrode (additional electrode, AdE) which is short-circuited with the MFC cathode and coupled with the MFC anode (MFC-AdE). The high working potential of BOx cathode and the low impedances of the additional capacitive electrode and the MFC anode permitted to achieve up to 19mW (84.4Wm−2, 152Wm−3), the highest power value ever reported for MFCs. Exploiting the supercapacitive properties of the MFC electrodes allows the system to be simpler, cheaper and more efficient without additional electronics management added with respect to an MFC/external supercapacitor coupling. The use of the AdE makes it possible to decouple energy and power and to achieve recharge times in the order of few seconds making the system appealing for practical applications.

Inocula selection in microbial fuel cells based on anodic biofilm abundance of Geobacter sulfurreducens

Microbial fuel cells (MFCs) rely on microbial conversion of organic substrates to electricity. The optimal performance depends on the establishment of a microbial community rich in electrogenic bacteria. Usually this microbial community is established from inoculation of the MFC anode chamber with naturally occurring mixed inocula. In this study, the electrochemical performance of MFCs and microbial community evolution were evaluated for three inocula including domestic wastewater (DW), lake sediment (LS) and biogas sludge (BS) with varying substrate loading (Lsub) and external resistance (Rext) on the MFC. The electrogenic bacterium Geobacter sulfurreducens was identified in all inocula and its abundance during MFC operation was positively linked to the MFC performance. The LS inoculated MFCs showed highest abundance (18%±1%) of G. sulfurreducens, maximum current density [Imax=(690±30)mA·m−2] and coulombic efficiency (CE=29%±1%) with acetate as the substrate. Imax and CE increased to (1780±30)mA·m−2 and 58%±1%, respectively, after decreasing the Rext from 1000Ω to 200Ω, which also correlated to a higher abundance of G. sulfurreducens (21%±0.7%) on the MFC anodic biofilm. The data obtained contribute to understanding the microbial community response to Lsub and Rext for optimizing electricity generation in MFCs.

Enhanced removal of petroleum hydrocarbons using a bioelectrochemical remediation system with pre-cultured anodes

Bioelectrochemical remediation (BER) systems such as microbial fuel cells (MFCs) have recently emerged as a green technology for the effective remediation of petroleum hydrocarbon contaminants (PH) coupled with simultaneous energy recovery. Recent research has shown that biofilms previously enriched for substrate degrading bacteria resulted in excellent performance in terms of substrate removal and electricity generation but the effects on hydrocarbon contaminant degradation were not examined. Here we investigate the differences between enriched biofilm anodes and freshly inoculated new anodes in diesel fed single chamber mediatorless microbial fuel cells (DMFC) using various techniques for the enhancement of PH contaminant remediation with concomitant electricity generation. An anodophilic microbial consortium previously selected for over a year through continuous culturing with a diesel concentration of about 800mgl−1 and which now showed complete removal of this concentration of diesel within 30days was compared to that of a freshly inoculated new anode MFC (showing 83.4% removal of diesel) with a simultaneous power generation of 90.81mW/m2 and 15.04mW/m2 respectively. The behaviour of pre-cultured anodes at a higher concentration of PH (8000mgl−1) was also investigated. Scanning electron microscopy observation revealed a thick biofilm covering the pre-cultured anodic electrode but not the anode from the freshly inoculated MFC. High resolution imaging showed the presence of thin 60nm diametre pilus-like projections emanating from the cells. Anodic microbial community profiling confirmed that the selection for diesel degrading exoelectrogenic bacteria had occurred. Identification of a biodegradative gene (alkB) provided strong evidence of the catabolic pathway used for diesel degradation in the DMFCs.

Bifunctional Manganese Ferrite/Polyaniline Hybrid as Electrode Material for Enhanced Energy Recovery in Microbial Fuel Cell.

Microbial fuel cells (MFCs) are emerging as a sustainable technology for waste to energy conversion where electrode materials play a vital role on its performance. Platinum (Pt) is the most common material used as cathode catalyst in the MFCs. However, the high cost and low earth abundance associated with Pt prompt the researcher to explore inexpensive catalysts. The present study demonstrates a noble metal-free MFC using a manganese ferrite (MnFe2O4)/polyaniline (PANI)-based electrode material. The MnFe2O4 nanoparticles (NPs) and MnFe2O4 NPs/PANI hybrid composite not only exhibited superior oxygen reduction reaction (ORR) activity for the air cathode but also enhanced anode half-cell potential upon modifying carbon cloth anode in the single-chambered MFC. This is attributed to the improved extracellular electron transfer of exoelectrogens due to Fe(3+) in MnFe2O4 and its capacitive nature. The present work demonstrates for the first time the dual property of MnFe2O4 NPs/PANI, i.e., as cathode catalyst and an anode modifier, thereby promising cost-effective MFCs for practical applications.

Real-time monitoring of phenazines excretion in Pseudomonas aeruginosa microbial fuel cell anode using cavity microelectrodes

Phenazines are a kind of metabolites that can mediate extracellular Pseudomonas aeruginosa (P. aeruginosa) cells in microbial fuel cells (MFCs). However, it is still not clear that whether and how the excretion profile of phenazines is affected by the operating MFC. Here, we report a real time analysis approach based on a cavity microelectrode electrochemical sensor to investigate the phenazines excretion behavior of P. aeruginosa during MFC operation. The phenazine concentration increases at first 72h, reaches a plateau and decreases after 120h and also shows local dependent variation. It is dependent on the MFC current generation profile but also affect by the biofilm formation. Accordingly, a mechanism about phenazines excretion in MFC anode and the phenazines mediated extracellular electron transfer of the P. aeruginosa anode is proposed. This work provides a novel strategy for self-mediated extracellular electron transfer analysis in the operating MFCs.

Recent Progress of Nanostructure Modified Anodes in Microbial Fuel Cells.

Microbial fuel cell (MFC) is a bio-electrochemical system which converts chemical energy into electrical energy by catalytic activity of microorganisms. Electrons produced by microbial oxidation from substrates such as organic matter, complex or renewable biomass are transferred to the anode. Protons produced at the anode migrate to the cathode via the wire and combine with oxygen to form water. Therefore MFC technologies are promising approach for generating electricity or hydrogen gas and wastewater treatment. Electrode materials are one of the keys to increase the power output of MFCs. To improve the cost effective performance of MFCs, various electrodes materials, modifications and configurations have been developed. In this paper, among other recent advances of nanostructured electrodes, especially carbon based anodes, are highlighted. The properties of these electrodes, in terms of surface characteristics, conductivity, modifications, and options were reviewed. The applications, challenges and perspectives of the current MFCs electrode for future development in bio or medical field are briefly discussed.

Nitrogen doped graphene sheets as metal free anode catalysts for the high performance microbial fuel cells

The doping of nitrogen over the graphene sheets was achieved by plasma enhanced chemical vapor deposition (CVD) technique and the resultant N doped graphene nanosheets (NGNS) were exploited as metal free biocompatible anode catalysts in microbial fuel cells (MFC). The wrinkled, open-porous, and cross linked network structure was observed for the NGNS as evidenced from the electron microscopic images. The doping of nitrogen on crumpled graphene layers induced the structural disorders and number of defects, which facilitated the electrical conductivity and catalytic activity of prepared NGNS and the N-doping over GNS was confirmed from XPS, FT-IR, UV–Vis and XRD techniques. The electrocatalytic activity of prepared nanostructures toward glucose oxidation based on Escherichia coli was evaluated by using cyclic voltammetry, revealing that NGNS exhibited the maximum electrooxidation current. The effective doping of nitrogen on graphene layers offered the maximum MFC power density of 1008 mW/m2 at a current density of 6300 mA/m2 and the hydrophobic properties of said catalyst enhanced the durability of MFCs. The exploitation of metal free NGNS as MFC anode catalysts geared up the new possibilities for the exploration of said catalysts in number of energy based applications.

Three-dimensional porous carbon nanotube sponges for high-performance anodes of microbial fuel cells

Highly-porous, light-weight, and inexpensive three-dimensional (3D) sponges consisting of interconnected carbon nanotubes (CNTs) without base materials are synthesized with a facile and scalable one-step chemical vapor deposition process as anode of microbial fuel cells (MFCs). The MFCs generates higher power densities of 2150 W m−3 (per anode volume) or 170 W m−3 (per anode chamber volume), comparable to those of commercial 3D carbon felt electrodes under the same conditions. The high performances are due to excellent charge transfer between CNTs and microbes owing to 13 times lower charge transfer resistance compared to that of carbon felt. The material cost of producing these CNT sponge estimates to be ∼$0.1/gcnt, significantly lower than that of other methods. In addition, the high production rate of about 3.6 g h−1 compared to typical production rate of 0.02 g h−1 of other CNT-based materials makes this process economically viable. The one-step synthesis method allowing self-assembly of 3D CNT sponges as they grow is low cost and scalable, making this a promising method for manufacturing high-performance anodes of MFCs, with broad applicability to microbial electrochemical systems in general.

Bioelectricity-generating behavior of a chemically modified carbon black anode in microbial fuel cells

The poor stability of the current output in microbial fuel cells (MFCs) inhibits its development and application on a large scale. In this work, a carbon black (CB) MFC anode was chemically activated using HNO3 and KOH as pretreatment agents at low temperature, and further modification was made by Fe3O4 addition to the host CB matrix. The enhanced anodic capacitance contributes to a steady power output with neither overshoot nor undershoot below 1.1 F/cm2. This resulted from the introduction of oxygen(nitrogen)-associated functionalities and the improvement of the surface wettability by the activation treatment. The chemical modification of a CB anode provides a feasible way to optimize power production and anodic capacitance in MFCs.

Conducting Polymers As Electrode Modifiers for the Enhanced Microbial Fuel Cell Performance

The low power density of a microbial fuel cell (MFC) compared to other fuel cells has been a problem for this technology to be implanted in the real world despite the fact that it has many merits as an alternative energy source such as environmental sustainability and carbon neutrality. The main reason lies in the slow electron transfer (ET) kinetics at the anode and the cathode. Electrons produced from the oxidation of organic matters by the bacterial biofilm on the anode are transferred to the cathode where oxygen reduction reaction (ORR) takes place. Thus fast ET at both electrodes is very important to increase current density that leads to enhanced power density. Here we show how polyaniline (PANI) and polypyrrole (Ppy) can be utilized as electrode modifiers to greatly improve MFC performance.First, we have used PANI and Ppy to modify anodes. When Ppy was applied to the anode in a mediator-type MFC using Proteus vulgaris as a biocatalyst, a large enhancement in power density was observed. A dramatic power enhancement was resulted from the electrodeposited Ppy onto the reticulated vitreous carbon (RVC) electrode. Our obtained maximum power density of 1.2 mW cm−3 is the highest value among the reported ones for the similar system. From impedance measurements, enhancement was attributed to the decrease in charge transfer resistance. More practical MFCs are single chamber and mediatorless type MFCs with a biofilm formed from activated sludge. We prepared polyaniline/carbon black (PANI/C) composite and applied it to carbon cloth anode. It shortened start-up period and significantly enhanced power density from 764 mW m-2 to 1277 mW m-2. Enhances performance was also attributed to fast electron transfer to the anode through PANI. The anode surface was characterized by employing various surface characterization techniques such as scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The power output depended upon the amount of PANI/C, showing a highest value at 0.2 mg cm-2. Coulombic efficiency was more than 30% at 4.3 A m-2.Second, PANI was also utilized as an ORR catalyst for an MFC cathode. We used polyaniline nanofibers (PANInf) synthesized by interfacial polymerization and prepared PANInf/Carbon black composite for the cathode. Higher electrocatalytic activity for the oxygen reduction compared to pristine PANInf was resulted, thus leading to a large power density enhancement 185 mW m−2 for the pristine PANInf to 496 mW m−2 for the composite material. Although the power density was still lower than when conventional Pt catalyst was used (604.3 mW m−2), a facile bulk synthesis and cheaper price would make PANInf/C an alternative to Pt when a large scale application comes to an issue.PANI was also used as a support to incorporate compounds that have high catalytic activity toward oxygen reduction. Iron phthalocyanine (FePc) has been known as effective oxygen reduction catalyst. FePc was incorporated into Polyaniline/carbon black (PANI/C) composite. Thus prepared (PANI/C/FePc) was used as a catalyst for the ORR in an air–cathode microbial fuel cell (MFC). The electrocatalytic activity of the PANI/C/FePc toward the ORR was compared with carbon-supported FePc. The ORR overpotential was decreased and current density was greatly increased, indicating that polyaniline plays a key role in ORR reactions. This PANI/FePc/C composite was also well adopted as a cathode material in MFCs. The maximum power density of 630.5 mW m−2 with the PANI/C/FePc cathode was higher than that of 336.6 mW m−2 with the C/FePc cathode because of enhanced ORR activity. We compared monetary aspect per power for these materials. It turned out that the power per cost of the PANI/C/FePc cathode is 7.5 times greater than that of the Pt cathode. Thus, the PANI/C/FePc can be a potential alternative to Pt in MFCs.We found PANInf could be a useful material for modifying the interior of the three-dimensional anode. Reticulated vitreous carbon (RVC) is an ideal material in that it has many interconnected pores inside so that substrate can freely flow through the pores. The PANInf layer was easily formed on the interior surface of the RVC on which a stable and robust bacterial biofilm was formed, giving higher power density.In conclusion, conducting polymers have been proven very promising materials for the MFC power enhancement. Electron transfer barrier at the anode and cathode can be lowered when conducting polymers are used. Modification of these polymers with foreign species can further increase power density.

Improving the Performance of Microbial Fuel Cells through Anode Manipulation

The continued focus on microbial fuel cells (MFCs) is due to their applications in power generation and simultaneous wastewater treatment. In the past decade, MFCs have been developed as a new class of energy devices and hold promise for broad applications in bioremediation, bioproduction, and biosensing. Despite the advances, the overall performance of MFCs is still limited, and particularly the energy loss at anode, where electrons are generated, is a restriction. Recent progress on MFC anodes has led to several effective approaches to improve MFC performance. In this Minireview, we discuss the performance losses in MFC anodes from the electrochemical point of view and then focus on the main strategies developed to overcome the anode performance losses. We also discuss the potential directions of future research on MFC anodes.

Facile Fabrication of Graphene-Containing Foam as a High-Performance Anode for Microbial Fuel Cells.

Facile fabrication of novel three-dimensional anode materials to increase the bacterial loading capacity and improve substrate transport in microbial fuel cells (MFCs) is of great interest and importance. Herein, a novel graphene-containing foam (GCF) was fabricated easily by freeze-drying and pyrolysis of a graphene oxide-agarose gel. Owing to the involvement of graphene and stainless-steel mesh in the GCF, the GCF shows high electrical conductivity, enabling the GCF to be a conductive electrode for MFC applications. With the aid of agarose, the GCF electrode possesses a supermacroporous structure with pore sizes ranging from 100-200 μm and a high surface area, which greatly increase the bacterial loading capacity. Cell viability measurements indicate that the GCF possesses excellent biocompatibility. The MFC, equipped with a 0.4 mm-thick GCF anode, shows a maximum area power density of 786 mW m(-2) , which is 4.1 times that of a MFC equipped with a commercial carbon cloth anode. The simple fabrication route in combination with the outstanding electrochemical performance of the GCF indicates a promising anode for MFC applications.

Effects of NaCl concentration on anode microbes in microbial fuel cells.

Understanding of how operational parameters affect the composition of exoelectrogenic microbes is an important step in the development of efficient microbial fuel cells (MFCs). In the present study, single-chamber MFCs were inoculated with rice paddy-field soil and continuously supplied with an acetate medium containing different concentrations of NaCl (0–1.8 M). Polarization analyses showed that power output increased as the NaCl concentration increased to 0.1 M, while it was markedly diminished over 0.3 M. The increase in power output was associated with an increased abundance of anode microbes as assessed by protein assays. Notably, the power increase was also accompanied by an increase in the abundance ratio of Geobacter bacteria to total anode bacteria as assessed by pyrosequencing of 16S rRNA gene amplicons and specific quantitative PCR. Although most Geobacter species are known to exhibit high growth rates in freshwater media without NaCl, the present study shows that 0.1 M NaCl facilitates the growth of Geobacter in MFC anode biofilms. This result suggests that the optimum salt concentration in MFC is determined by the balance of two factors, namely, the solution conductivity and salt tolerance of exoelectrogens.

Effect of Carbon Sources on the Catalytic Performance of Ni/β-Mo2C.

In this paper, Ni/β-Mo2C(S) and Ni/β-Mo2C(G) were prepared from solution-derived precursor with two different carbon sources (starch and glucose) and tested as anodic noble-metal-free catalysts in air-cathode microbial fuel cells (MFCs). The carburized catalyst samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and Brunauer-Emmett-Teller (BET). The activity of the electrocatalyst towards the oxidation of several common microbial fermentation products (formate, lactate, and ethanol) was studied for MFC based on Klebsiella pneumoniae conditions. The composite MFC anodes were fabricated, and their catalytic behavior was investigated. With different carbon sources, the crystalline structure does not change and the crystallinity and surface area increase. The electrocatalytic experiments show that the Ni/β-Mo2C(G) gives the better bio- and electrocatalytic performance than Ni/β-Mo2C(S) due to its higher crystallinity and BET surface area.

Bacterial and archaeal guilds associated with electrogenesis and methanogenesis in paddy field soil

It is tempting to develop green energy biotechnology to supplement the depletion of fossil fuel resources and to reduce the greenhouse gas emissions. It has been recently demonstrated that paddy soil can be used to construct the sediment-type microbial fuel cells (MFCs). The mechanisms involved in electricity generation and its effects on methanogenesis, however, remain poorly understood. In the present experiment, we constructed paddy soil MFCs to evaluate the effect of MFC on CH4 emission and to determine the bacterial and archaeal populations associated with MFC anodes. We found that electrical current in MFCs increased rapidly in three weeks, while only minor current was detected in MFCs without rice plants. Methane emission decreased in closed circuit MFCs compared with open circuit MFCs that did not have electricity output. Molecular approaches revealed that the upstream fermentation bacterial community was not significantly affected by MFCs. However, the relative abundances of Geobacteraceae increased markedly in MFCs; and concurrently the classical syntrophs including Syntrophaceae, Syntrophorhabdaceae, Syntrophobacteraceae and Syntrophomonadaceae increased. Among methanogenic archaea, the relative abundance of Methanosaetaceae increased significantly in closed circuit MFCs compared with open-circuit MFCs. Collectively, our study suggests that the activities of electron-transferring bacteria and archaea are significantly promoted in paddy soil MFCs.

Controlled modification of carbon nanotubes and polyaniline on macroporous graphite felt for high-performance microbial fuel cell anode

Polyaniline (PANI) was electropolymerized on the surface of macroporous graphite felt (GF) followed by the electrophoretic deposition of carbon nanotubes (CNTs). The as-prepared macroporous material was characterized by scanning electron microscopy, water contact angle goniometry and electrochemical techniques. Upon the modification of PANI, a rough and nano-cilia containing film is coated on the surface of the graphite fibers, transforming the surface from hydrophobic to hydrophilic. The subsequent modification by CNTs increases the effective surface area and electrical conductivity of the resulting material. The power output of a mediator-free dual-chamber microbial fuel cell (MFC) constructed from the GF anode and an exoelectrogen Shewanella putrefaciens increases drastically with the CNT modification. The CNT/PANI/GF MFC attains an output voltage of 342 mV across an external resistor of 1.96 kΩ constant load, and a maximum power density of 257 mW m−2, increased by 343% and 186%, compared to that of the pristine GF MFC and the PANI/GF MFC, respectively. More bacteria are attached on the CNT/PANI/GF anode than on the PANI/GF anode during the working of the MFC. This strategy provides an easy scale-up, simple and controllable method for the preparation of high-performance and low-cost MFC anodes.