Anode Of Microbial Fuel Cell Research Articles

Dye degradation and electricity generation using microbial fuel cell with graphene oxide modified anode

In this study the graphene oxide (GO) assisted biodegradation of brilliant green dye was studied in microbial fuel cell (MFC). The degradation of dye in MFC was characterized by reduction in chemical oxygen demand (COD) and further analysis was performed by UV–Vis, and FTIR spectroscopy. The successful removal study of the brilliant green dye shows the superior bioactive characteristics of GO on MFC anode. The redox activity was studied during biofilm development via cyclic voltammetry (CV). However, the rational power density of 0.04 mW/cm−2 was calculated corresponding to current density of 0.00025 mA/cm2. These observations indicated the influence of GO on MFC performance, which could further be improved by incorporating various GO composite materials. This study also highlights operational sustainability and an economical process to fabricate MFCs for their practical applications.

Polypyrrole/sargassum activated carbon modified stainless-steel sponge as high-performance and low-cost bioanode for microbial fuel cells

Anode materials, as the core component of microbial fuel cells (MFCs), have huge impacts on power generation performance and overall cost. Stainless-steel sponge (SS) can be a promising material for MFC anodes, due to its open continuous three-dimensional structure, high conductivity and low cost. However, poor biocompatibility limits its application. In this paper, a polypyrrole/sargassum activated carbon modified SS anode (Ppy/SAC/SS) is developed by electrochemical polymerization of pyrrole on the SS with the SAC as a dopant. The maximum power density achieved with the Ppy/SAC/SS anode is 45.2 W/m3, which is increased by 2 orders of magnitude and 2.9 times compared with an unmodified SS anode and a solely Ppy modified SS anode (Ppy/SS), respectively. In addition, the Ppy/SAC layer effectively eliminates electrochemical corrosion of the SS substrate. Electrochemical impedance spectroscopy reveals that Ppy/SAC modification decreases electron transfer resistance between the bacteria and the electrode. Furthermore, in vivo fluorescence imaging indicates that a more uniform biofilm is formed on the Ppy/SAC/SS compared to the unmodified SS and Ppy/SS. Due to the low cost of the materials, easy fabrication process and relatively high performance, our developed Ppy/SAC/SS can be a cost efficient anode material for MFCs in practical applications.

Simultaneous use of a crossflow filtration membrane as microbial fuel cell anode – Permeate flow leads to 4-fold increased current densities

A new concept for the combination of membrane bioreactors and microbial fuel cells is introduced, that aims at the production of electricity for reducing the overall energy consumption of wastewater treatment. In contrast to previous approaches, the anode is integrated as microfiltration membrane in sidestream crossflow configuration. Using a stainless steel filtration membrane with G. sulfurreducens and an acetate-based synthetic medium, up to 4-fold higher current densities are achieved. In a standard setup without filtration, a membrane of filter grade 1 µm shows current densities of 5.8 A m−2 ± 0.5 A m−2 compared to >11 A m−2 when it is used simultaneously as membrane filter. With smaller pore sizes of filter grade 0.5 µm, 4.4 A m−2 ± 0.5 A m−2 in a standard setup and >15 A m−2 in a filtration setup are achieved. The permeate flow was identified as the main parameter leading to increased current densities.

Molybdenum anode: a novel electrode for enhanced power generation in microbial fuel cells, identified via extensive screening of metal electrodes

BackgroundMetals are considered a suitable anode material for microbial fuel cells (MFCs) because of their high electrical conductivity. However, only a few types of metals have been used as anodes, and an extensive screening of metals has not yet been conducted. In this study, to develop a new metal anode for increased electricity generation in MFCs, 14 different metals (Al, Ti, Fe, Ni, Cu, Zn, Zr, Nb, Mo, Ag, In, Sn, Ta, and W) and 31 of their oxidized forms were comprehensively tested. Oxidized-metal anodes were prepared using flame oxidation, heat treatment, and electrochemical oxidation. The selected anodes were further evaluated in detail using air–cathode single-chambered MFCs.ResultsThe untreated Mo and electrochemically oxidized Mo anodes showed high averages of maximum power densities in the screening test, followed by flame-oxidized (FO) W, FO-Fe, FO-Mo, and Sn-based anodes. The untreated Mo and FO-W anodes were selected for further evaluation. X-ray analyses revealed that the surface of the Mo anode was naturally oxidized in the presence of air, forming a layer of MoO3, a known oxidation catalyst. A high maximum power density (1296 mW/m2) was achieved using the Mo anode in the MFCs, which was superior to that obtained using the FO-W anode (1036 mW/m2). The Mo anode, but not the FO-W anode, continued to produce current without detectable corrosion until the end of operation (350 days). Geobacter was abundant in both biofilms on the Mo and FO-W anodes, as analyzed by high-throughput sequencing of the 16S rRNA gene.ConclusionsThe screening test revealed that Mo, W, Fe, and Sn are useful MFC anode materials. The detailed analyses demonstrated that the Mo anode is a high-performance electrode with structural simplicity and long-term stability in MFCs. The anode can be easily prepared by merely shaping Mo materials to the desired forms. These properties would enable the large-scale preparation of the anode, required for practical MFC applications. This study also implies the potential involvement of Geobacter in the Mo and W cycles on Earth.

Exploring the use of polyaniline-modified stainless steel plates as low-cost, high-performance anodes for microbial fuel cells

The provision of optimum medium for microbial growth and maintenance of long-term stability for microbial fuel cells (MFCs) is very much dependent on the chosen anode material. However, the chosen material must also be readily available and cheap in order to attract wider use and broader adoption of MFCs. In this study, we explored the use of polyaniline (PANi) modified stainless steel plates (SS-Ps) as potential low-cost anodes for MFCs, with capability for effective promotion of microbial growth and retention of long-term stability. Careful and selective choice of acid and aniline concentrations for galvanostatic polymerisation produced highly uniform and adherent conductive PANi coating on SS-P which are desirable for use as anodes in MFC. The resulting PANi modified SS-P (SS-P/PANi) was evaluated as a low-cost anode for MFCs in a simulated wastewater which composed of a M9 media and 4% landfill leachate. The SS-P/PANi anode performed efficiently in a MFC, achieving a 13-fold higher current generation than with a pristine SS-P anode during the startup phase. Also, it achieved higher OCVmax of 730 ± 42 mV, jmax of 0.14 ± 0.12 mA cm−2 and a Pmax of 0.078 ± 0.011 mW cm−2. In comparison, the SS-P anode achieved lower OCVmax of 649 ± 37 mV, jmax of 0.009 ± 0.011 mA cm−2 and Pmax of 0.010 ± 0.008 mW cm−2. Furthermore, the achieved current and power densities with the SS-P/PANi anode were superior to those obtained with a previously reported PANi modified stainless steel fibre felt (SSFF) anode. Thus, demonstrating the suitability of the SS-P/PANi electrode for adoption as a low-cost, high-performance anode for MFCs.

Enhanced removal of p-nitrophenol in a microbial fuel cell after long-term operation and the catabolic versatility of its microbial community

Electrochemical technology was employed to degrade p-nitrophenol (PNP) in a microbial fuel cell (MFC). Approximately 81% of 50 mg/L PNP was degraded within 24 h by the anode at 28 °C and pH 7.0. A significant interaction of temperature, pH, and initial PNP concentration was found for the degradation of PNP, and a theoretical maximum degradation rate of 95% was achieved at 34.63 °C, pH 7.4, and an initial PNP concentration of 126.96 mg/L after a 3-day incubation. Moreover, after long-term operation, the anodic biofilm exhibited the ability to degrade various aromatic compounds, including chloramphenicol, benzofluorfen, fluoxastrobin, and flubendiamide. High-throughput sequencing analysis showed that functional bacteria of the genera Corynebacterium, Comamonas, Chryseobacterium and Rhodococcus predominated in the MFC anode biofilm. The complex syntrophic interactions among these functional bacteria were important for efficient removal of organic compounds. In conclusion, the MFC exhibited the potential to treat aromatic contaminants due to its energy recovery and the catabolic versatility of the anodic biofilm.

Polypyrrole modified stainless steel as high performance anode of microbial fuel cell

Stainless steel(SS) is regarded as an eligible anode material in microbial fuel cells (MFCs), owing to its low cost and high mechanical strength. However, its poor biocompatibility and low corrosion resistance still limited its further application. Here we reported a unique-structural SS-based anode for high-performance MFCs by in-situ electrochemical depositing polypyrrole (PPy) onto SS (PPy/SS). By PPy modification, the corrosion resistance and the power generation performance of the anode can be significantly improved. The maximum power density of MFCs with PPy/SS anode reached a value of 1190.94 mW m−2, which was about 29 times higher than that with bare SS anode. In addition, the results of scanning electron microscopy (SEM), cyclic-voltammetry (CV) and electrochemical impedance spectroscopy (EIS) characterizations showed that the MFC with PPy/SS anode had lower internal resistance and higher capacitance than that with bare SS anode. These ensured the PPy/SS improved corrosion resistance, biocompatibility, power density and made it a promising anode material for MFCs.

Two-stage pretreatment of excess sludge for electricity generation in microbial fuel cell

ABSTRACTThermophiles hydrolysis and acidogens fermentation were sequentially adopted to pretreat excess sludge for microbial fuel cell (MFC) electricity production. The results indicated that MFC fed with the thermophiles-acidogens pretreated sludge (MFC AB), reached a higher removal of ammonia nitrogen than the MFC fed with the heating hydrolysis and acidogens fermentation pretreated sludge (MFC NB). However, compared with the MFC AB, MFC NB presented a better performance for removal of soluble chemical oxygen demand (SCOD) (90.08%) and protein (82.42%). As for the electricity production, MFC NB obtained higher voltage of 0.632 V and maximum power density with 1.05 W/m3 while MFC AB reached maximum voltage of 0.373 V and maximum power density of 0.58 W/m3. Bacterial 16S rRNA-based molecular microbial techniques showed that microbial communities on both MFC anode biofilms was diverse and different. The cooperation of fermentation bacteria and electricigen Shewanella baltica in the MFC NB may have contributed towards the improvement of electricity generation.

Tailoring of pore structure in mesoporous carbon for favourable flavin mediated interfacial electron transfer in microbial fuel cells.

Mesoporous carbon (MC) is supposed to be a good candidate for microbial fuel cell (MFC) anodes as it possesses a large specific area for the redox reaction of the electron shuttles and should deliver high power density. However, the power generation performance of MC anodes is often un-satisfying. It seems that a large portion of the pore surface is not available for anodic redox reaction but the reason is not clear. Here, three MCs with different pore sizes and pore shapes were fabricated and used to explore the effect of the pore structure on the bioelectrocatalysis in Shewanella putrefaciens CN32 MFCs. It is interesting that MC with 40–60 nm spheric pores (MC-III) possesses superior bio-electrocatalytic performance to the CMK-3 (MC-I with 3 nm channel like pores) and the one with 14 nm spheric pores (MC-II) although the specific surface area of MC-III is lower than MC-II and MC-I. The reason might be that the MC-III provides a more favorable pore structure than the other two MCs for flavin based redox reaction at the interface between the biofilm and the electrode. As a result, the MC-III anode delivered the highest power density at around 1700 mW m−2, which is 1.6 fold higher than that of the MC-I anode. A possible mechanism for the pore shape/size dependent interfacial electron transfer process has also been proposed. This work reveals that spheric mesopores with large pore width could be more favorable than the narrow channel-like pores for flavin based interfacial electron transfer in biofilm anodes, which will provide some insights for the design of the mesoporous anode in MFCs.

Degradation characterization and pathway analysis of chlortetracycline and oxytetracycline in a microbial fuel cell.

The wide presence of antibiotics in the environment has raised concerns about their potential impact on ecological and human health. This study was conducted to evaluate the degradation of antibiotics (chlortetracycline (CTC) and oxytetracycline (OTC)) in microbial fuel cells (MFCs) and the change of toxicity. The degradation rates of 60 mg L−1 CTC and OTC in the MFCs were 74.2% and 78%, respectively, within 7 days. The degradation ability of the two antibiotics followed the order of OTC > CTC. Toxicity test results of the zebrafish illustrated the toxicity of OTC and CTC was largely eliminated by MFC treatment. Furthermore, possible degradation pathways of CTC and OTC were speculated using LC-MS analysis. High-throughput sequencing analysis indicated that Petrimonas, Azospirillum, Dokdonella, Burkholderia and Stenotrophomonas were the predominant genera in the MFC anode biofilm. Therefore, this work is of great significance for future studies on the treatment of antibiotics in wastewater by MFCs.

Nanoporous gold electrode prepared from gold compact disk as the anode for the microbial fuel cell

The electrodes (anode and cathode) have an important role in the efficiency of a microbial fuel cell (MFC), as they can determine the rate of charge transfer in an electrochemical process. In this study, nanoporous gold electrode, prepared from commercially available gold-made compact disk, is utilized as the anode in a two-chamber MFC. The performance of nanoporous gold electrode in the MFC is compared with that of gold film, carbon felt and acid-heat-treated carbon felt electrodes which are usually employed as the anode in the MFCs. Electrochemical surface area of nanoporous gold electrode exhibits a 7.96-fold increase rather than gold film electrode. Scanning electron microscopy analysis also indicates the homogeneous biofilm is formed on the surface of nanoporous gold electrode, while the biofilm formed at the surface of acid-heat-treated carbon felt electrode shows rough structure. Electrochemical studies show although modifications applied on carbon felt electrodes improve its performance, nanoporous gold electrode, due to its structure and better electrochemical properties, acts more efficiently as the MFC’s anode. The maximum power density produced by nanoporous gold anode is 4.71 mW m−2 at current density of 16.00 mA m−2, while this value for acid-heat-treated carbon felt anode is 3.551 mW m−2 at current density of 9.58 mA m−2.

Microbial fuel cells: enhancement with a polyaniline/carbon felt capacitive bioanode and reduction of Cr(VI) using the intermittent operation

With the increasing concern for energy sources, waste management, the search for novel technological solutions continues. Microbial fuel cell is a new biotechnology that utilizes bacteria as catalysts to decompose organic substrate and simultaneously harvest electricity. Anodes play an important role in deciding the microbial fuel cell. In this paper, the cumulative charge of the polyaniline-modified bioanode from the chronoamperometric experiment with 20 min of charging and 20 min of discharging is 13,930.1 C m−2, much higher than that of bare carbon felt anode (5908.1 C m−2). Then, we investigated two different operations of the microbial fuel cell (intermittent and continuous operations) to remove Cr(VI) in the cathode chamber. Under intermittent operation, 71.1% of Cr(VI) was reduced, which was 1.13-fold greater than under continuous operation. This study suggested that the microbial fuel cell anode containing polyaniline pseudo-capacitive materials has the potential for storing energy from wastewater and releasing the energy in a short time to an electronic device. These favorable Cr(VI) removal results contribute to the capacitive anode in the charging process of intermittent operation, produce and store electricity simultaneously, and release a greater portion of the electricity stored in the anode than under continuous operation in the process of degradation, thereby gaining a larger current. Here we show that a microbial fuel cell containing a pseudo-capacitive material, such as polyaniline, functions as a biocapacitor, stores bioelectrons generated from microbial oxidation of substrate, and releases the accumulated charge simultaneously.

Macroscale porous carbonized polydopamine-modified cotton textile for application as electrode in microbial fuel cells

The anode material is a crucial factor that significantly affects the cost and performance of microbial fuel cells (MFCs). In this study, a novel macroscale porous, biocompatible, highly conductive and low cost electrode, carbonized polydopamine-modified cotton textile (NC@CCT), is fabricated by using normal cheap waste cotton textiles as raw material via a simple in situ polymerization and carbonization treatment as anode of MFCs. The physical and chemical characterizations show that the macroscale porous and biocompatible NC@CCT electrode is coated by nitrogen-doped carbon nanoparticles and offers a large specific surface area (888.67 m2 g−1) for bacterial cells growth, accordingly greatly increases the loading amount of bacterial cells and facilitates extracellular electron transfer (EET). As a result, the MFC equipped with the NC@CCT anode achieves a maximum power density of 931 ± 61 mW m−2, which is 80.5% higher than that of commercial carbon felt (516 ± 27 mW m−2) anode. Moreover, making full use of the normal cheap waste cotton textiles can greatly reduce the cost of MFCs and the environmental pollution problem.

Electricity generation in microbial fuel cell systems with Thiobacillus ferrooxidans as the cathode microorganism

Microbial fuel cells (MFC) are systems that enable biochemical activities of bacteria to generate the electricity. These systems are of great interest because of their designs that enable biological activity in organic wastes to be transformed into direct electrical energy. In order to increase the commercial usage of MFCs, it is necessary to increase the power output of the system. So as to improve MFC performance, used material selection, the pH value of the used bacterial medium and the choice of the appropriate substrate are very important. In this study, oxidation bacteria Thiobacillus ferrooxidans on the cathode and mixed culture bacteria on the anode of MFC were used. Different anode and cathode pH values were examined in MFC. Best open circuit potential result (0.8 V) was obtained at anode pH 8 and cathode pH 2 conditions. In addition, three different substrates had been used in the anode. In the conditions of acetate the most stable and high valued curve was obtained. The open circuit potential had reached 0.726 V, and power density had reached 0.88 mW/cm2.

Graphite Sheets as High‐Performance Low‐Cost Anodes for Microbial Fuel Cells Using Real Food Wastewater

AbstractGraphite paper is introduced as efficient and low‐cost anode in an air‐cathode microbial fuel cell (MFC) for simultaneous wastewater treatment and power generation using real food wastewater. Graphite paper as the cheapest investigated material provided the best electrochemical results in an MFC with an excellent open cell voltage. The significantly increased power generation could be attributed to the large surface area of the anode, leading to enhanced bacterial attachment on the graphite anode surface. Regarding wastewater treatment, the graphite anode exhibited the highest removal of organic pollutants and the highest coulombic efficiency. It shows an excellent efficiency as a bio‐anode in the air‐MFC for producing electricity and treating industrial wastewaters without requiring external mediators.

Effect of anodes decoration with metal and metal oxides nanoparticles on pharmaceutically active compounds removal and power generation in microbial fuel cells

Anodes modified with MnO2, Pd and Fe3O4 nanoparticles were used in microbial fuel cells (MFCs) and their effects on pharmaceutically active compounds (PhACs) removal and power generation were investigated. Results showed that anode decoration with MnO2, Fe3O4 and Pd led to different performance in removing PhACs from MFCs. Diclofenac (DCF), ibuprofen (IBF) and carbamazepine (CBZ) were more effectively removed in the MFCs with the MnO2, Fe3O4 or Pd anode compared to that with the carbon black (CB) modified control anode, with a removal of 81.5%–84.0% for CBZ, 48.7%–52.6% for DCF and 18.8%–20.1% for IBF, while the corresponding parts attained with the CB anode were 71.0%–78.5% for CBZ, 28.8% for DCF and 14.6% for IBF. Iohexol (IOX) was hardly removed in all the MFCs. When common non-conductive carrier (nonwoven) was used as the anode of MFCs, PhACs were less removed compared to the MFC systems, suggesting MFCs possess specially advantages over PhACs removal. The MFCs with the Pd, MnO2 and Fe3O4 anodes generated a maximum power density of 824 ± 36, 782 ± 37 and 728 ± 33 mW m−2, respectively, higher than that with the control anode (680 ± 28 mW m−2). High-throughput sequencing results showed that the MnO2 and Fe3O4 modified anodes especially enriched the exoelectrogen Geobacter (72.1%), while the Pd decorated anode enriched a high abundance of Geobacter (38.5%) and Sphaerochaeta (16.1%). Enhanced electron transfer, specially enriched microbial community, unique catalytic functions of the metal or metal oxides deposited on the anodes, may contribute to the enhanced performance of MFCs on power generation and PhACs removal.

Analysis of Anodes of Microbial Fuel Cells When Carbon Brushes Are Preheated at Different Temperatures

The anode electrode is one of the most important components in all microbial electrochemical technologies (METs). Anode materials pretreatment and modification have been shown to be an effective method of improving anode performance. According to mass loss analysis during carbon fiber heating, five temperatures (300, 450, 500, 600, and 750 °C) were selected as the pre-heating temperatures of carbon fiber brush anodes. Microbial fuel cell (MFC) reactors built up with these pre-heated carbon brush anodes performed with different power densities and Coulombic efficiencies (CEs). Two kinds of measuring methods for power density were applied, and the numerical values of maximum power densities diverged greatly. Reactors with 450 °C anodes, using both methods, had the highest power densities, and the highest CEs were found using 500 °C anode reactors. The surface elements of heat-treated carbon fibers were analyzed using X-ray photoelectron spectra (XPS), and C, O, and N were the main constituents of the carbon fiber. There were four forms of N1s at the surface of the polyacrylonitrile (PAN)-based carbon fiber, and their concentrations were different at different temperature samples. The microbial community of the anode surface was analyzed, and microbial species on anodes from every sample were similar. The differences in anode performance may be caused by mass loss and by the surface elements. For carbon brush anodes used in MFCs or other BESs, 450–500 °C preheating was the most suitable temperature range in terms of the power densities and CEs.

The Identification of Cable Bacteria Attached to the Anode of a Benthic Microbial Fuel Cell: Evidence of Long Distance Extracellular Electron Transport to Electrodes.

Multicellular, filamentous, sulfur-oxidizing bacteria, known as cable bacteria, were discovered attached to fibers of a carbon brush electrode serving as an anode of a benthic microbial fuel cell (BMFC). The BMFC had been operated in a temperate estuarine environment for over a year before collecting anode samples for scanning electron microscopy and phylogenetic analyses. Individual filaments were attached by single terminus cells with networks of pilus-like nano-filaments radiating out from these cells, across the anode fiber surface, and between adjacent attachment locations. Current harvesting by the BMFC poised the anode at potentials of ~170–250 mV vs. SHE, and these surface potentials appear to have allowed the cable bacteria to use the anode as an electron acceptor in a completely anaerobic environment. A combination of catalyzed reporter deposition fluorescent in situ hybridization (CARD-FISH) and 16S rRNA gene sequence analysis confirmed the phylogeny of the cable bacteria and showed that filaments often occurred in bundles and in close association with members of the genera Desulfuromonas. However, the Desulfobulbaceae Operational Taxonomic Units (OTUs) from the 16S sequencing did not cluster closely with other putative cable bacteria sequences suggesting that the taxonomic delineation of cable bacteria is far from complete.

Activated microporous-mesoporous carbon derived from chestnut shell as a sustainable anode material for high performance microbial fuel cells

Microbial fuel cells (MFCs) are promising biotechnologies tool to harvest electricity by decomposing organic matter in waste water, and the anode material is a critical factor in determining the performance of MFCs. In this study, chestnut shell is proposed as a novel anode material with mesoporous and microporous structure prepared via a simple carbonization procedure followed by an activation process. The chemical activation process successfully modified the macroporous structure, created more mesoporous and microporous structure and decreased the O−content and pyridinic/pyrrolic N groups on the biomass anode, which were beneficial for improving charge transfer efficiency between the anode surface and microbial biofilm. The MFC with activated biomass anode achieved a maximum power density (23.6 W m−3) 2.3 times higher than carbon cloth anode (10.4 W m−3). This study introduces a promising and feasible strategy for the fabrication of high performance anodes for MFCs derived from cost-effective, sustainable natural materials.

Augmenting atrazine and hexachlorobenzene degradation under different soil redox conditions in a bioelectrochemistry system and an analysis of the relevant microorganisms

Soil microbial fuel cells (MFCs) are a sustainable technology that degrades organic pollutants while generating electricity. However, there have been no detailed studies of the mechanisms of pollutant degradation in soil MFCs. In this study, the effects of external resistance and electrode effectiveness on atrazine and hexachlorobenzene (HCB) degradation were evaluated, the performance of soil MFCs in the degradation of these pollutants under different soil redox conditions was assessed, and the associated microorganisms in the anode were investigated. With an external resistance of 20Ω, the degradation efficiencies of atrazine and HCB were 95% and 78%, respectively. The degradation efficiency, degradation rate increased with decreasing external resistance, while the half-life decreased. There were different degradation trends for different pollutants under different soil redox conditions. The fastest degradation rate of atrazine was in the upper MFC section (aerobic), whereas that of HCB was in the lower MFC section (anaerobic). The results showed that electrode effectiveness played a significant role in pollution degradation. In addition, the microbial community analysis demonstrated that Proteobacteria, especially Deltaproteobacteria involved in current generation was extremely abundant (27.49%) on soil MFC anodes, although the percentage abundances of atrazine degrading Rhodocyclaceae (8.77%), Desulfitobacterium (0.64%), and HCB degrading Desulfuromonas (0.73%), were considerably lower. The results of the study suggested that soil MFCs can enhance the degradation of atrazine and HCB, and bioelectrochemical reduction was the main mechanism for the pollutants degradation.