Anode Of Microbial Fuel Cell Research Articles

Lysine-modified TiO2 nanotube array for optimizing bioelectricity generation in microbial fuel cells

As the carrier of electroactive bacteria and part of the electron migration path, the anode is a restricting factor for the power density of microbial fuel cells (MFCs). In this study, carbon-coated TiO2 nanotube array (TNT/HL) was synthesized by anodization and thermal treatment, for use as anodes in MFCs to promote power production. Due to the sucker structure and the carbon attachment, the TNT/HL anode increased the bacterial loading capacity when exposed under lamplight or natural light. Single-chamber MFCs with the TNT/HL anode achieved a maximum power density of 0.88 W/m2, which is much higher than that of MFCs using the common commercial carbon cloth (CC) anode (0.61 W/m2). Further investigation attributed such superior results to the better biocompatibility, enlarged electroactive surface, decreased electric resistance and Tafel slope of the as-prepared TNT/HL anode. This study introduces a promising anode material for MFCs with high conductivity, high current density, and fast extracellular electron transfer (EET).

Enhancement of Power Generation in Microbial Fuel Cells through Supplementation of <i>Platycodon grandiflorum</i> in Doraji Roots

The current study reports the evidence of enhancement in power generation from cellulosic biomass in microbial fuel cell (MFC) systems by supplementing dried Doraji (Platycodon grandiflorum) roots powder. Mediator-less two chamber H-type MFCs were prepared using rumen fluid as anode inocula to convert finely ground pine tree (Avicel) at 2% (w/v) to electricity. Dried Doraji roots were ground to pass 1 mm sieve and added to the anode of MFC at 0.1% w/v dosage for treatment. MFC power and current across an external resistor were measured daily for 10 d. At the end of incubation on d10, collected gases were measured for total gas volume and analyzed for gas composition on gas chromatography. Supplementation of Doraji roots powder to MFC anode chamber increased power generation and CO2 production. Over the 10d experimental period, power density normalized to anode surface area were between 17.0 and 37.7 with average of 32.5 mW/m2 in Doraji MFCs, and between 16.8 and 19.8 with average of 18.2 mW/m2 in control group. CO2 production increased and methane to CO2 ratio decreased in Doraji root treatment comparing to control group. These observations imply that Doraji root components would inhibit methanogenesis and alter microbial fermentation of cellulose compounds favorable to produce bioenergy efficiently in MFC.

Electrochemical Characterization of Heat-Treated Metal and Non-Metal Anodes using Mud in Microbial Fuel Cell

Microbial fuel cells (MFCs) have a high potential application for simultaneous wastewater treatment and electricity generation. However, the choice of the electrode material and its design is critical and directly affect their performance. As an electrode of MFCs, the anode material with surface modifications is an attractive strategy to improve the power output. In this study, stainless steel (SS) and carbon steel (CS) was chosen as a metal anode, while graphite felt (GF) was used as a common anode. Heat treatment was performed to convert SS, CS and GF into efficient anodes for MFCs. The maximum current density and power density of the MFC-SS were achieved up till 762.14 mA/m2 and 827.25 mW/m2, respectively, which were higher than MFC-CS (641.95 mA/m2 and 260.14 mW/m2) and MFC-GF (728.30 mA/m2 and 307.89 mW/m2). Electrochemical impedance spectroscopy of MFC-SS showed better catalytic activity compared to MFC-CS and MFC-GF anode, also supported by cyclic voltammetry test.

Novel Gas Diffusion Cloth Bioanodes for High-Performance Methane-Powered Microbial Fuel Cells.

Microbial fuel cells (MFCs) are a promising technology that converts chemical energy into electricity. However, up to now only few MFCs have been powered by gas fuels, such as methane, and their limited performance is still challenged by the low solubility and bioavailability of gases. Here, we developed a gas diffusion cloth (GDC) anode to significantly enhance the performance of methane-powered MFCs. The GDC anode was constructed by simply coating waterproof GORE-TEX cloth with conductive carbon cloth in one step. After biofilm enrichment, the GDC anodes obtained a methane-dependent current up to 1130.2 mA m-2, which was 165.2 times higher than conventional carbon cloth (CC) anodes. Moreover, MFCs equipped with GDC anodes generated a maximum power density of 419.5 mW m-2. Illumina high-throughput sequencing revealed that the GDC anode biofilm was dominated mainly by Geobacter, in contrast with the most abundant Methanobacterium in planktonic cells. It is hypothesized that Methanobacterium reversed the methanogenesis process by transferring electrons to the anodes, and Geobacter generated electricity via the intermediates (e.g., acetate) of anaerobic methane oxidation. Overall, this work provides an effective route in preparing facile and cost-effective anodes for high-performance methane MFCs.

Packed anode derived from cocklebur fruit for improving long-term performance of microbial fuel cells

Packed anode of microbial fuel cells (MFCs), commonly with a dense structure, suffers from the clogging, resulting in unsatisfied long-term stability of MFCs. Herein, we fabricate a biochar-based packed anode with a loose structure to enhance the long-term performance of MFCs equipped with packed anodes. The biochar, derived from cocklebur fruit, endows the packed anode with a loose structure but excellent conductivity. Once incorporated into MFCs, the biochar-based packed anode can yield comparable performance to benchmark materials. Particularly, the biochar-based MFCs present no obvious decrease of the power output during 150 days’ operation, which is attributed to the clogging-resistant effect induced by the loose structure of biochar-based anode. The cocklebur fruit-derived biochar can be a promising candidate for MFC anodes, and should facilitate both scaling-up and practical applications of MFCs.

Effect of Zeolite-Fe on graphite anode in electroactive biofilm development for application in microbial fuel cells

The performance of microbial fuel cells (MFCs) is highly dependent on the electrode materials. The electrode surface can be modified to provide a favorable environment for biofilms to enhance electron transfer from the bacteria to the anode. In this work, Faujasite zeolite-Y (ZY) was exchanged with iron (Fe) and was used to modify glassy carbon/graphite electrodes (GC/gr-ZYFe) evaluating its effect in electroactive biofilm development for application in microbial fuel cells. The novel material was evaluated as an anode in MFCs by comparing its performance with GC/gr and GC/gr-ZY electrodes. The results show that when using a GC/gr-ZYFe electrode, an electroactive biofilm with good electrochemical activity for acetate degradation can be generated on the electrode surface. The maximum current density obtained with a GC/gr-ZYFe-BF electrode (where BF is biofilm) was 7.7 times higher than that of a GC/gr anode. The modification generates a less hydrophobic electrode surface that facilitates microbial cell attachment, thereby improving bioelectricity production. By using scanning electron microscopy, a homogeneous microbial community with bacteria that had a similar short rod-shaped morphology was observed. Furthermore, electrochemical impedance spectroscopy demonstrated that the charge transfer resistance (Rct) decreased as the biofilm grew, revealing that the presence of the biofilm facilitated the electrochemical reaction. After 7 days of MFC operation, the GC/gr-ZYFe bioanode showed a reduction in Rct from 212.9 ± 1.81 Ω to 151.5 ± 1.46 Ω, which was 2.4 times lower than that achieved with GC/gr. The biofilm on GC/gr-ZYFe was characterized using cyclic voltammetry, and the results showed a larger oxidation peak (169.8 μA cm−2) than that of the GC/gr electrode (36.5μA cm−2), further supporting the better electron-transfer properties of the modified electrode. Additionally, this result confirms the capability of biofilms to act as bioelectrocatalysts under acetate-oxidizing conditions.

Effects of the Structure of TiO2 Nanotube Arrays on Its Catalytic Activity for Microbial Fuel Cell.

To enhance the microbial fuel cell (MFC) for wastewater treatment and chemical oxygen demand degradation, TiO2 nanotubes arrays (TNA) are successfully synthesized on Ti foil substrate by the anodization process in HF and NH4F solution, respectively (hereafter, denoted as TNA‐HF and TNA‐NF). The differences between the two kinds of TNA are revealed based on their morphologies and spectroscopic characterizations. It should be highlighted that 3D TNA‐NF with an appropriate dimension can make a positive contribution to the high photocatalytic activity. In comparison with the TNA‐HF, the 3D TNA‐NF sample exhibits a significant enhancement in current generation as the MFC anode. In particular, the TNA‐NF performs nearly 1.23 times higher than the TNA‐HF, and near twofold higher than the carbon felt. It is found that the two kinds of TiO2‐based anodes have different conductivities and corrosion potentials, which are responsible for the difference in their current generation performances. Based on the experimental results, excellent stability, reliability, and low cost, TNA‐NF can be considered a promising and scalable MFC bioanode material.

Transition metal nanoparticles doped carbon paper as a cost-effective anode in a microbial fuel cell powered by pure and mixed biocatalyst cultures

The poor wettability and high cost of the carbonaceous electrodes materials prohibited the practical applications of microbial fuel cells (MFCs) on large scale. Here, a novel nanoparticles of metal sheathed with metal oxide is electrodeposited on carbon paper (CP) to introduce as high-performance anodes of microbial fuel cell (MFC). This thin layer of metal/metal oxide significantly enhance the microbial adhesion, the wettability of the anode surface and decrease the electron transfer resistance. The investigation of the modified CP anodes in an air-cathode MFCs fed by various biocatalyst cultures shows a significant improving in the MFC performance. Where, the generated power and current density was 140% and 210% higher as compared to the pristine CP. Mixed culture of exoelectrogenic microorganism in wastewater exhibited good performance and generated higher power and current density compared to yeast as pure culture. The excellent capacitance with a distinctive nanostructure morphology of the modified-CP open an avenues for practical applications of MFCs.

Bread-derived 3D macroporous carbon foams as high performance free-standing anode in microbial fuel cells

Microbial fuel cells (MFCs) are a promising clean energy source to directly convert waste chemicals to available electric power. However, the practical application of MFCs needs the increased power density, enhanced energy conversion efficiency and reduced electrode material cost. In this study, three-dimensional (3D) macroporous N, P and S co-doped carbon foams (NPS-CFs) were prepared by direct pyrolysis of the commercial bread and employed as free-standing anodes in MFCs. As-obtained NPS-CFs have a large specific surface area (295.07 m2 g−1), high N, P and S doping level, and excellent electrical conductivity. A maximum areal power density of 3134 mW m−2 and current density of 7.56 A m−2 are generated by the MFCs equipped with as-obtained NPS-CF anodes, which is 2.57- and 2.63-fold that of the plain carbon cloth anodes (areal power density of 1218 mW m−2 and current density of 2.87 A m−2), respectively. Such improvement is explored to mainly originate from two respects: the good biocompatibility of NPS-CFs favors the bacterial adhesion and enrichment of electroactive Geobacter species on the electrode surface, while the high conductivity and improved bacteria-electrode interaction efficiently promote the extracellular electron transfer (EET) between the bacteria and the anode. This study provides a low-cost and sustainable way to fabricate high power MFCs for practical applications.

Quick start-up and performance of microbial fuel cell enhanced with a polydiallyldimethylammonium chloride modified carbon felt anode

It is of significant importance to simultaneously shorten the start-up time and enhance the electricity generation performance for practical application of microbial fuel cell (MFC). In this paper, the polydiallyldimethylammonium chloride (PDDA) modified carbon felt (PDDA-CF) electrode was prepared and used as the anode of PDDA-MFC. The anode significantly enhanced the start-up speed and electricity generation and dye wastewater degradation performances of the PDDA-MFC. The start-up time of PDDA-MFC is only 9 h, which is only 7.5% that of the unmodified carbon felt anode MFC (CF-MFC). The charge transfer resistance, the maximum output voltage and the maximum output power density of PDDA-MFC were 9.7 Ω, 741 mV and 537.8 mW m-2 respectively, which were 70.3% lower than, 1.7 times and 3.3 times greater than those of CF-MFC respectively. In addition, the color and chemical oxygen demand (COD) removal rates of Reactive Brilliant Red X-3B for PDDA-MFC reached 95.94% and 64.24% at 24 h respectively, which were 41.5% and 51.2% higher than those of CF-MFC respectively. Due to the electrostatic attraction of PDDA, the adhesion and metabolic mass transfer rate of exoelectrogens are accelerated, thus the PDDA-CF electrode has excellent electrochemical properties and bio-affinity. This paper provides a new idea to enhance the start-up speed and performance of MFC simultaneously.

Impact of Ohmic Resistance on Measured Electrode Potentials and Maximum Power Production in Microbial Fuel Cells.

Low solution conductivity is known to adversely impact power generation in microbial fuel cells (MFCs), but its impact on measured electrode potentials has often been neglected in the reporting of electrode potentials. While errors in the working electrode (typically the anode) are usually small, larger errors can result in reported counter electrode potentials (typically the cathode) due to large distances between the reference and working electrodes or the use of whole cell voltages to calculate counter electrode potentials. As shown here, inaccurate electrode potentials impact conclusions concerning factors limiting power production in MFCs at higher current densities. To demonstrate how the electrochemical measurements should be adjusted using the solution conductivity, electrode potentials were estimated in MFCs with brush anodes placed close to the cathode (1 cm) or with flat felt anodes placed further from the cathode (3 cm) to avoid oxygen crossover to the anodes. The errors in the cathode potential for MFCs with brush anodes reached 94 mV using acetate in a 50 mM phosphate buffer solution. With a felt anode and acetate, cathode potential errors increased to 394 mV. While brush anode MFCs produced much higher power densities than flat anode MFCs under these conditions, this better performance was shown primarily to result from electrode spacing following correction of electrode potentials. Brush anode potentials corrected for solution conductivity were the same for brushes set 1 or 3 cm from the cathode, although the range of current produced was different due to ohmic losses with the larger distance. These results demonstrate the critical importance of using corrected electrode potentials to understand factors limiting power production in MFCs.

Application of 3D Printed Porous Copper Anode in Microbial Fuel Cells

In this study, 3D printing technique was utilized to fabricate three-dimensional porous electrodes for microbial fuel cells with UV curable resin, followed by copper electroless plating. A maximum voltage of 62.9 ± 2.5 mV and a power density of 6.45 ± 0.5 mWm-2 were achieved for MFCs with 3D printed porous copper (3D-PPC) anode, which were 8.3 and 12.3-fold higher than copper mesh electrode, respectively. This illustrated the great advantage of 3D porous anodes in MFCs compared to flat anode structures. Besides, the biocompatibility of the copper anode with Shewanella oneidensis MR-1 was examined by comparing with carbon cloth, which produced a 3-fold larger maximum voltage and a ~10-fold higher power density vs. 3D-PPC anode and thus indicated the possible copper corrosion during MFC operation. ICP-MS analysis of MFC solution revealed the high concentration of 732µg/L copper ions detected in the MFC effluent. This result, coupled with EDX showing the lower copper content on the 3D-PPC anode surface after >15 days of MFC operation, confirmed the copper dissolving behavior in MFC. MR-1 biofilm formation under copper suppression was finally characterized by SEM and less biofilm was observed on copper anodes, illustrating their poor biocompatibility, even though 3D printing technology and porous structures were quite promising for future scale-up.

Graphene Oxide/Polytetrafluoroethylene Composite Anode and Chaetoceros pre-Treated Anodic Inoculum Enhancing Performance of Microbial Fuel Cell

Graphene Oxide/Polytetrafluoroethylene Composite Anode and Chaetoceros pre-Treated Anodic Inoculum Enhancing Performance of Microbial Fuel Cell

Ternary Composite of Polyaniline Graphene and TiO2 as a Bifunctional Catalyst to Enhance the Performance of Both the Bioanode and Cathode of a Microbial Fuel Cell

Microbial fuel cells (MFCs) are a potential sustainable energy resource by converting organic pollutants in wastewater to clean energy. The performance of MFCs is influenced directly by the electrode material. In this study, a ternary PANI-TiO2-GN nanocomposite was used successfully to improve the performance of both the cathode and anode MFC. The PANI-TiO2-GN catalyst exhibited better oxygen reduction reaction activity in the cathode, particularly as a superior catalyst for improved extracellular electron transfer to the anode. This behavior was attributed to the good electronic conductivity, long-term stability, and durability of the composite. The immobilization of bacteria and catalyst matrix in the anode facilitated more extracellular electron transfer (EET) to the anode, which further improved the performance of the MFCs. The application of PANI-TiO2-GN as a bifunctional catalyst in both the cathode and anode helped decrease the cost of MFCs, making it more practical.

Characteristics of Poly(3,4-ethylenedioxythiophene) Modified Stainless Steel as Anode in Air-Cathode Microbial Fuel Cells

Poly(3,4-ethylenedioxythiophene) (PEDOT) was electrochemically polymerized to in situ modify stainless steel (SS) plate electrode to improve its microbial bioelectrocatalytic activity as high-performance anode in microbial fuel cells. After modification, the surface of the electrode became rougher and showed better wettability. The electrochemical characteristics of PEDOT modified SS (PEDOT/SS) and bare SS electrodes were studied by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and Tafel corrosion polarization curves, respectively. It has been demonstrated that PEDOT modification could increase electrode capacitance and reduce electron transfer resistances. Compared with untreated SS, PEDOT/SS electrode showed better anticorrosion property as well. The modified anode produced a maximum power density of 608.6 mW/m2, which was about 6 times higher than bare SS anode. These results indicate that PEDOT treatment is an efficient method for SS to improve its performance as anode in MFCs.

High-performance microbial fuel cell anodes obtained from sewage sludge mixed with fly ash

Microbial fuel cells (MFCs) are promising for converting biomass energy into electricity, and have attracted much research interest. However, few inexpensive high-performance anode materials for MFCs exist. In this study, MFC anodes composed of sewage sludge and different contents of fly ash (0%, 20%, 40%, 60%, and 80%) are fabricated via a one-step carbonization method. The maximum current density of 25.5 A m−2 is achieved using the electrode with 20% fly ash, which is 37.5% higher than that of the electrode without fly ash. The improved anode performance is attributed to its good hydrophilicity, which is indicated by its water contact angle of less than 60°, facile adsorption of exoelectrogens, low electron transfer resistance, and good biocompatibility. In addition, the mechanical strength of the electrode with 20% fly ash is approximately 18 times that of the electrode without fly ash. This study reveals a promising method to fabricate high-performance MFC anodes and sheds light on the future development of MFCs using abundant municipal solid waste products.

Shortcut Biological Nitrogen Removal (SBNR) in an MFC Anode Chamber under Microaerobic Conditions: The Effect of C/N Ratio and Kinetic Study

In this work, the feasibility of the Shortcut Biological Nitrogen Removal (SBNR) in the anodic chamber of a Microbial Fuel Cell (MFC) was investigated. Thirty day experiments were carried out using synthetic wastewaters with a Total Organic Carbon vs. nitrogen ratio (TOC/N) ranging from 0.1 to 1. Ammonium, nitrite, nitrate, pH, and TOC were daily monitored. Results showed that microaerobic conditions in the anodic chamber favored the development of nitritation reaction, due to oxygen transfer from the cathodic chamber through the membrane. Nitritation was found to depend on TOC/N ratio: at TOC/N equal to 0.1 an ammonium removal efficiency of up to 76% was observed. Once the oxygen supply to the cathodic chamber was stopped, denitritation occurred, favored by an increase of the TOC/N ratio: a nitrite removal of 80.3% was achieved at TOC/N equal to 0.75. The presence of nitrogen species strongly affected the potential of the electrochemical system: in the nitritation step, the Open Circuit Voltage (OCV) decreased from 180 mV to 21 mV with the decrease of the TOC/N ratio in the investigated range. Lower OCV values were observed in the denitritation steps since the organic carbon acted as the energy source for the conversion of nitrite to nitrogen gas. A kinetic analysis was also performed. Monod and Blackman models described the ammonium and the organic carbon removal processes well during the nitritation step, respectively, while Blackman-Blackman fitted experimental results of the denitritation step better.

Microbiological aspects of thermophile pretreatment of activated sludge inhibiting electricity generation of microbial fuel cell.

Thermophile pretreatment of activated sludge greatly improves the biodegradability of sludge, but whether the pretreated products are suitable for the electricity generation of microbial fuel cells (MFCs) is still little known. In this study, municipal activated sludge pretreated by a thermophilic bacterium and heating, respectively, was separately fed into the MFCs. The performance of MFCs was examined and changes of anodic microbial communities were investigated with scanning electron microscopy and 16S rRNA gene high-throughput sequencing on the Illumina Miseq platform. The results showed that MFCs fed with heating-pretreated sludge performed preferably and the power density reached 0.91-2.86 W/m3. MFC anodes were covered with considerable Geobacter spp. However, the bioaugmentation of sludge with the thermophile was not able to support a high potential output although the pretreatment significantly increased the soluble chemical oxygen demand. The maximum power density approached 0.20 W/m3 even when the anolyte was regularly changed. It was observed that amending pH did not improve the performance of MFC. Investigation on this anodic microbial community found that the relative abundance of Lactobacillus spp. exceeded 91%. Consequently, the thermophile-pretreated products stimulated the growth of non-exoelectrogens and finally the niches of anodic biofilm were completely occupied by Lactobacillus spp.

Hierarchically Porous N-Doped Carbon Nanotubes/Reduced Graphene Oxide Composite for Promoting Flavin-Based Interfacial Electron Transfer in Microbial Fuel Cells.

Interfacial electron transfer between an electroactive biofilm and an electrode is a crucial step for microbial fuel cells (MFCs) and other bio-electrochemical systems. Here, a hierarchically porous nitrogen-doped carbon nanotubes (CNTs)/reduced graphene oxide (rGO) composite with polyaniline as the nitrogen source has been developed for the MFC anode. This composite possesses a nitrogen atom-doped surface for improved flavin redox reaction and a three-dimensional hierarchically porous structure for rich bacterial biofilm growth. The maximum power density achieved with the N-CNTs/rGO anode in S. putrefaciens CN32 MFCs is 1137 mW m-2, which is 8.9 times compared with that of the carbon cloth anode and also higher than those of N-CNTs (731.17 mW m-2), N-rGO (442.26 mW m-2), and the CNTs/rGO (779.9 mW m-2) composite without nitrogen doping. The greatly improved bio-electrocatalysis could be attributed to the enhanced adsorption of flavins on the N-doped surface and the high density of biofilm adhesion for fast interfacial electron transfer. This work reveals a synergistic effect from pore structure tailoring and surface chemistry designing to boost both the bio- and electrocatalysis in MFCs, which also provide insights for the bioelectrode design in other bio-electrochemical systems.

Sulfate-reducing mixed communities with the ability to generate bioelectricity and degrade textile diazo dye in microbial fuel cells

The biotreatment of recalcitrant wastes in microbial fuel cells (MFCs) rather than chemical, physical, and advanced oxidation processes is a low-cost and eco-friendly process. In this study, sulfate-reducing mixed communities in MFC anodic chamber were employed for simultaneous electricity generation, dye degradation, and sulfate reduction. A power generation of 258 ± 10 mW/m2 was achieved under stable operating conditions in the presence of electroactive sulfate-reducing bacteria (SRB). The SRBs dominant anodic chambers result in dye, chemical oxygen demand (COD), and sulfate removal of greater than 85% at an initial COD (as lactate)/SO42− mass ratio of 2.0 and dye concentration of 100 mg/L. The effects of the COD/SO42− ratio (5.0:1.0–0.5:1.0) and initial diazo dye concentration (100–1000 mg/L) were studied to evaluate and optimize the MFC performance. Illumina Miseq technology for bacterial community analysis showed that Proteobacteria (89.4%), Deltaproteobacteria (52.7%), and Desulfovibrio (48.2%) were most dominant at phylum, class, and genus levels, respectively, at the MFC anode. Integration of anaerobic SRB culture in MFC bioanode for recalcitrant chemical removal and bioenergy generation may lead to feasible option than the currently used technologies in terms of overall pollutant treatment.