Electrodes In Microbial Fuel Cells Research Articles

Microbial fuel cells for inexpensive continuous in-situ monitoring of groundwater quality

Online monitoring of groundwater quality in shallow wells to detect faecal or organic pollution could dramatically improve understanding of health risks in unplanned peri-urban settlements. Microbial fuel cells (MFC) are devices able to generate electricity from the organic matter content in faecal pollution making them suitable as biosensors. In this work, we evaluate the suitability of four microbial fuel cell systems placed in different regions of a groundwater well for the low-cost monitoring of a faecal pollution event. Concepts created include the use of a sediment/bulk liquid MFC (SED/BL), a sediment/sediment MFC (SED/SED), a bulk liquid/air MFC (BL/Air), and a bulk liquid/bulk liquid MFC (BL/BL). MFC electrodes assembly aimed to use inexpensive, durable, materials, which would produce a signal after a contamination event without external energy or chemical inputs. All MFC configurations were responsive to a contamination event, however SED/SED and BL/Air MFC concepts failed to deliver a reproducible output within the tested period of time. BL/BL MFC and SED/BL MFCs presented an increase in the average current after contamination from −0.75 ± 0.35 μA to −0.66 ± 0.41 μA, and 0.07 ± 0.2 mA to 0.11 ± 0.03 mA, respectively. Currents produced by the SED/BL MFC (SMFC) were considerably higher than for the BL/BL MFCs, making them more responsive, readable and graphically visible. A factorial design of experiments (DOE) was applied to evaluate which environmental and design factors had the greatest effect on current response in a contamination event. Within the ranges of variables tested, salinity, temperature and external resistance, only temperature presented a statistically significant effect (p = 0.045). This showed that the biosensor response would be sensitive to fluctuations in temperature but not to changes in salinity, or external resistances produced from placing electrodes at different distances within a groundwater well.

Bioelectricity Generation using Carbon Felt Electrode in Microbial Fuel Cell (MFC) Inoculated with Mixed Cultures

Microbial fuel cell (MFC) that was configured with the carbon felt electrode and the cation exchange membrane, and inoculated with mixed culture was demonstrated to yield bioelectricity. The cell was operated under four external loads with pHs ranging from 4 to 10 and the total cell operation was monitored up to 25 days. The presented results revealed that the potentiality of maximum current and power production was achieved while hexacyanoferrate(III) used as a cathodic reaction and at neutral pH condition of media. The maximum current density 2.5 Am -2 and power density 1410 mWm -2 were observed on the 25 th day at an anode potential of -378 mV. Stable and steady power was produced by MFC on the day 22 nd to 25 th when cell operated at 250 Ω external load. The internal resistance of the fuel cell was decreased with the increase of the operation time. Coulombic efficiency (CE %) was found 22.70 % at the stable phase of fuel cell operation. Citation:  Pramanik, S. K., and Rana, M. M. (2017). Bioelectricity Generation using Carbon Felt Electrode in Microbial Fuel Cell (MFC) Inoculated with Mixed Cultures. Trends in Renewable Energy, 3, 129-140. DOI: 10.17737/tre.2017.3.2.0039

Comparative metabolic state of microflora on the surface of the anode electrode in a microbial fuel cell operated at different pH conditions.

The metabolic state of microflora (mixed microbial cultures) in microbial fuel cells (MFCs) is currently unclear. Metabolomic analyses were conducted of microflora growing on the anodic electrodes of MFCs operated at pH 7.0, 5.5, or 4.0 and utilizing starch as the major carbon substrate. A much higher current was produced at pH 7.0 than at pH 5.5 and 4.0, correlating with an increased population ratio of Geobacter species to the total bacteria growing on the electrode. Most intracellular metabolites related to the tricarboxylic acid (TCA) cycle were present at a higher level at pH 7.0 than at pH 5.5 and 4.0, and the levels of metabolites correlated well with the obtained current densities. A high intracellular adenosine triphosphate (ATP)/adenosine diphosphate (ADP) ratio at pH 7.0, compared to at pH 5.5 and 4.0, likewise supported current production. Overall, the metabolomic analyses demonstrated that activation of the TCA cycle and increased ATP generation are critical parameters for electricity generation by microflora.Electronic supplementary materialThe online version of this article (doi:10.1186/s13568-016-0299-4) contains supplementary material, which is available to authorized users.

Advances in Graphene/Graphene Composite Based Microbial Fuel/Electrolysis Cells

AbstractThe modifications of electrodes using graphene and graphene composites in microbial fuel cells (MFCs) and microbial electrolysis cells (MECs) have been widely applied for enhancing the electrochemical catalytic activity and performance of MFCs and MECs. Graphene as one of advanced materials has shown outstanding features for promoting practical applications of MFCs. This review summarizes the modification methods and characterization methods of graphene and related graphene composites on electrode surfaces in MFCs and MECs. The performance improvements of MFCs and MECs by various graphene related composites have been reviewed, which will provide an efficient guide for selecting suitable graphene material to modify electrodes in MFCs and MECs for improving their performance.

Applications of Graphene-Modified Electrodes in Microbial Fuel Cells.

Graphene-modified materials have captured increasing attention for energy applications due to their superior physical and chemical properties, which can significantly enhance the electricity generation performance of microbial fuel cells (MFC). In this review, several typical synthesis methods of graphene-modified electrodes, such as graphite oxide reduction methods, self-assembly methods, and chemical vapor deposition, are summarized. According to the different functions of the graphene-modified materials in the MFC anode and cathode chambers, a series of design concepts for MFC electrodes are assembled, e.g., enhancing the biocompatibility and improving the extracellular electron transfer efficiency for anode electrodes and increasing the active sites and strengthening the reduction pathway for cathode electrodes. In spite of the challenges of MFC electrodes, graphene-modified electrodes are promising for MFC development to address the reduction in efficiency brought about by organic waste by converting it into electrical energy.

Carbon-Based Air-Breathing Cathodes for Microbial Fuel Cells

A comparison between different carbon-based gas-diffusion air-breathing cathodes for microbial fuel cells (MFCs) is presented in this work. A micro-porous layer (MPL) based on carbon black (CB) and an activated carbon (AC) layer were used as catalysts and applied on different supporting materials, including carbon cloth (CC), carbon felt (CF), and stainless steel (SS) forming cathode electrodes for MFCs treating urine. Rotating ring disk electrode (RRDE) analyses were done on CB and AC to: (i) understand the kinetics of the carbonaceous catalysts; (ii) evaluate the hydrogen peroxide production; and (iii) estimate the electron transfer. CB and AC were then used to fabricate electrodes. Half-cell electrochemical analysis, as well as MFCs continuous power performance, have been monitored. Generally, the current generated was higher from the MFCs with AC electrodes compared to the MPL electrodes, showing an increase between 34% and 61% in power with the AC layer comparing to the MPL. When the MPL was used, the supporting material showed a slight effect in the power performance, being that the CF is more powerful than the CC and the SS. These differences also agree with the electrochemical analysis performed. However, the different supporting materials showed a bigger effect in the power density when the AC layer was used, being the SS the most efficient, with a power generation of 65.6 mW·m−2, followed by the CC (54 mW·m−2) and the CF (44 mW·m−2).

(Science for Solving Society’s Problems Challenge Grant Winner) Self-Powered Supercapacitive Microbial Fuel Cell

A self-powered supercapacitive microbial fuel cell (MFC) is here reported. Microbial fuel cell (MFC) is an interesting bio-electrochemical technology that is used for wastewater treatment with simultaneous organic removal and electricity generation. Due to the much lower current/power production compared to hydrogen and methanol fuel cells, a smart design is desired to increase performance up to the levels required for real applications. The most used method to store/deliver energy from an MFC at high rate is coupling it with an external supercapacitor with capacitances in the order of Farads1. The main disadvantage of this approach is that high capacitance supercapacitors require long time to be recharged at the low MFC current regimes. This makes the MFC-Supercapacitor system working with long recharge stand-by time and low switch-on/off frequency. Here, a microbial fuel cell has been integrated with internal supercapacitor (SC)2. The MFC anode was the SC negative electrode. Its potential (≈-0.5 V vs Ag/AgCl) was related to the presence of bacteria that consumed the oxygen present into the solution and colonize the carbon brush electrode. The MFC cathode, an air-breathing cathode working at ≈+0.1 V vs Ag/AgCl, was the SC positive electrode. Single chamber MFC filled with 50% volume of 0.1M phosphate buffer saline (PBS) solution and 50% activated sludge was used during the experiments. Galvanostatic discharges were performed with current pulses up to 4 mA. An MFC with activated carbon (AC)-based cathode featured a maximum power of 2.98 Wm-2 (5.36 Wm-3) which was mainly affected by the cathode ohmic losses. In order to further enhance the output, two strategies were adopted. The first one was simply enhance the overall cell voltage by utilizing cathode catalysts with higher potential like non-platinum based catalyst (iron-aminoantipyrine (Fe-AAPyr))3 or enzymatic-based catalyst (bilirubin oxidase (BOx)4). The second option was to utilize an additional high capacitive electrode of low resistance, short-circuited with the cathode, coupled with the negative electrode (MFC-AdE). The AdE used was a carbon brush coated with AC. The first option brought to the increase of the voltage from 0.6V with AC to 0.68V with Fe-AAPyr and to 0.78V with BOx cathode. Figure 1 showed the discharge of the MFC using Fe-AAPyr cathode with and without the AdE. Consequently, maximum power (Pmax) achieved 6.53 Wm-2 (11.76 Wm-3) and 4 Wm-2 (7.2 Wm-3) using BOx and Fe-AAPyr, respectively. The use of AdE significantly reduced the cell ohmic drop and led to a much important improvement (Figure 1). Pulses discharges up to 45 mA were performed. The cell resistance decreased by one order of magnitude allowing higher current pulses and power generated. In fact, Pmax was 84.4 Wm-2 (152 Wm-3) with BOx cathode, 62.2 Wm-2 (112 Wm-3) with Fe-AAPyr and 26.7 Wm-2 (49 Wm-3) with AC cathode. The addition of the AdE is a smart and easy way to overcome the ohmic losses of the system. This current/power output is in the same range of MFCs coupled with external supercapacitors. The main advantage of the system here reported is the much shorter recharging time (in the order of seconds/minutes) of interest for applications that have to be powered with more frequent pulses, like sensors. Also, utilization of the MFC electrodes as the supercapacitor electrodes makes the system simpler and more compact. Acknowledments CS was funded by the Electrochemical Society and Bill & Melinda Gates Foundation under initiative: “Applying Electrochemistry to Complex Global Challenges”. FS acknowledges financial support by Università di Bologna (Researcher Mobility Program).

Bioanode of polyurethane/graphite/polypyrrole composite in microbial fuel cells

Polyurethane (PU) foams were coated with graphite, and pyrrole monomer was subsequently polymerized onto its surface by chemical oxidization to obtain nanostructured polyurethane/graphite/polypyrrole (PU/Graph/PPy) composites, which were used for anaerobic microorganisms grown and tested as anodes in microbial fuel cells (MFC) using municipal wastewater as fuel. The effects of oxidizing agent type (ammonium persulfate and FeCl3) used in pyrrole polymerization on the performance of electrodes in MFC were studied. Composites were characterized by Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM), and by the four-point probes to determine conductivity. It was observed from SEM analysis that globular nanostructures of PPy were formed onto PU surface with average diameters between 120 and 450 nm, which are typical of aqueous polymerization of pyrrole monomer. The highest output power density observed in MFCs was 305.5 mW/m3 for the composite synthesized using FeCl3 as the oxidant, and 128.6 mW/m3 using the composite obtained with ammonium persulfate as oxidizing; the corresponding chemical oxygen demand (COD) removal were 48.2 and 45.5%, respectively. The calculated coulombic efficiency for PU/Graph/PPy composite obtained with FeCl3 as oxidant was of 9.4%. Internal resistance of MFC using the composite obtained with FeCl3 as oxidant was determined by linear sweep voltammetry (LSV) and the variable resistance (VR) methods, giving 4.8 and 2.9 kO, respectively, with average maximum power density of 237.5 mW/m3.

Metabolic flux change in Klebsiella pneumoniae L17 by anaerobic respiration in microbial fuel cell

The metabolic flux in microbial fuel cells (MFCs) is significantly different from conventional fermentation because the electrode in MFCs acts as a terminal electron acceptor. In this study, the difference in the carbon metabolism of Klebsiella pnuemoniae L17 (Kp L17) during growth in MFCs and conventional bioreactors was studied using glucose as the sole carbon and energy source. For metabolic flux analysis (MFA), the in silico metabolic flux model of Kp L17 was also constructed. The MFC bioreactor operated in oxidative mode, where electrons are removed by the anode electrode, generated a smaller quantity of reductive metabolites (e.g., lactate, 2,3-butanediol and ethanol) compared to the conventional fermentative bioreactor (non-MFC). Stoichiometric analysis indicated that the cellular metabolism in MFC had partially (or significantly) shifted to anaerobic respiration from fermentation, the former of which was similar to that often observed under micro-aerobic conditions. Electron balance analysis suggested that 30% of the electrons generated from glucose oxidation were extracted from the microbe and transferred to the electrode. These results highlight the potential use of MFCs in regulating the carbon metabolic flux in a bioprocess.

Biochar Based Microbial Fuel Cell for Enhanced Wastewater Treatment and Nutrient Recovery

Waste-wood derived biochar was evaluated for the first time as both an anode and cathode material, simultaneously, in an overflow style microbial fuel cell (MFC) using actual industrial wastewater. Results show that the average chemical oxygen demand (COD) removal was 95% with a reduction rate of 0.53 kg·COD·m−1·d−1 in closed operation mode. The ammonia and phosphorous reductions from wastewater was 73% and 88%, respectively. Stable power production was observed with a peak power density measured at 6 W/m3. Preliminary contributions of physical, biological, and electrochemical COD removals were evaluated, and the results show such combined mechanisms give BC an advantage for MFC applications. Nutrient recovery data showed high levels of macronutrients adsorbed onto the spent biochar electrodes, and phosphorus concentration increased from 0.16 g·kg−1 in raw BC to up to 1.9 g·kg−1 in the cathode. These findings highlight the use of biochar as electrodes in MFCs to facilitate simultaneous wastewater treatment and power production with additional agronomic benefits.

Development of Gold Electrodes for Microbial Fuel Cells

The microbial fuel cell (MFC) has been an important subject of study in the last decades because of its technological significance that one can produce hydrogen or electricity by wastewater treatment (bio-remediation). One of the main issues for the application of these devices on large scale is the processes and materials for the electrode fabrication. The cathode for MFC requires a catalyst to perform the reduction reaction and this work presents a simple technique to obtain thin layers of gold (TLG) supported on glass. This technique was employed to obtain TLG with different thicknesses from 848 nm to the thinnest of 137 nm. Since the gold of the TLGs presented adherence issues, a successful thermal treatment with different temperatures from 150-300 ºC was developed to avoid the gold detachment. The TLGs were tested as cathodes in a MFC and a maximum Voc of 431 mV and an Isc of 10 × 10−2 mA were obtained. The process to obtain TLGs presented here has probed to be a good option for this application since the thickness obtained and the accessible material (glass) employed as support offers a solution to the costs and the scaling issues.

EVALUATION OF BIOELECTROGENIC POTENTIAL OF FOUR INDUSTRIAL EFFLUENTS AS SUBSTRATE FOR LOW COST MICROBIAL FUEL CELLS OPERATION

Microbial Fuel Cells (MFCs), the bioelectrochemical devices for conversion of waste into electricity through bacterial metabolic activity can use substrates with different complexity and strength. Wastewaters with moderate to high organic content can be exploited as MFC substrates. In this study, four different industrial wastewaters (from a chemical company, milk industry, soyabased food and soft-drink company and laundry) with different compositions were used as substrates in identical MFCs. In the design of MFC, carbon cloth was used as anode and low-cost carbon based, non-platinized electrode as air cathode. Anode and cathode were separated by an ion permeable membrane Zirfon , directly attached on the cathode. After initial operation with 10 mM acetate as substrate, the cells were switched to real industrial wastewaters without pre-treatment. When operational, an electrochemically active biofilm and anode open circuit voltage (OCV) of -500 mV vs. Ag/AgCl. OCV was obtained which recovered after dropping in all cells, showing the ability of anodic bacteria to utilize industrial wastewaters as substrate. A maximum power of 419 mW m-2 was obtained with milk industry wastewater, while the electrodes in MFC with chemical industry wastewater were corroded after few days of operation suggesting that every wastewater is not suitable as substrate for electricity production and treatment in MFCs.

Applications of Graphene-Based Hybrid Material as Electrodes in Microbial Fuel Cells

Applications of Graphene-Based Hybrid Material as Electrodes in Microbial Fuel Cells

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.

Electrode materials for microbial fuel cells: nanomaterial approach

Microbial fuel cell (MFC) technology has the potential to become a major renewable energy resource by degrading organic pollutants in wastewater. The performance of MFC directly depends on the kinetics of the electrode reactions within the fuel cell, with the performance of the electrodes heavily influenced by the materials they are made from. A wide range of materials have been tested to improve the performance of MFCs. In the past decade, carbon-based nanomaterials have emerged as promising materials for both anode and cathode construction. Composite materials have also shown to have the potential to become materials of choice for electrode manufacture. Various transition metal oxides have been investigated as alternatives to conventional expensive metals like platinum for oxygen reduction reaction. In this review, different carbon-based nanomaterials and composite materials are discussed for their potential use as MFC electrodes.

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.

Operational, design and microbial aspects related to power production with microbial fuel cells implemented in constructed wetlands

This work aimed at determining the amount of energy that can be harvested by implementing microbial fuel cells (MFC) in horizontal subsurface constructed wetlands (HSSF CWs) during the treatment of real domestic wastewater. To this aim, MFC were implemented in a pilot plant based on two HSSF CW, one fed with primary settled wastewater (Settler line) and the other fed with the effluent of a hydrolytic up-flow sludge blanket reactor (HUSB line). The eubacterial and archaeal community was profiled on wetland gravel, MFC electrodes and primary treated wastewater by means of 16S rRNA gene-based 454-pyrosequencing and qPCR of 16S rRNA and mcrA genes. Maximum current (219 mA/m2) and power (36 mW/m2) densities were obtained for the HUSB line. Power production pattern correlated well with water level fluctuations within the wetlands, whereas the type of primary treatment implemented had a significant impact on the diversity and relative abundance of eubacteria communities colonizing MFC. It is worth noticing the high predominance (13–16% of relative abundance) of one OTU belonging to Geobacter on active MFC of the HUSB line that was absent for the settler line MFC. Hence, MFC show promise for power production in constructed wetlands receiving the effluent of a HUSB reactor.

Graphene-based electrode materials for microbial fuel cells

Microbial fuel cells (MFCs) are environmentally friendly technology capable of converting chemical energy stored in waste-waters directly into electrical energy by using microorganisms as biocatalysts. However, the overall low power density of the MFC and the high cost of its components are two major barriers for its commercialization. Among all the factors, the electrodes (cathode and anode) materials play the significant role in affecting the performance of MFCs. Recently, the performance of MFCs has been improved by using graphene-based electrodes that are more conductive and mechanically stable with larger surface area and higher electrocatalytic activity compared to the conventional carbon materials. This paper provides an overview of recent research progress in graphene-based materials as electrodes for MFCs, which will be the promising candidates for developing MFCs and other bioelectrochemical systems to achieve sustainable water/wastewater treatment and bioenergy production.

Fabrication of Bacteria-imprinted Polymer Coated Electrodes for Microbial Fuel Cells

The feasibility of using microorganisms for electrical power generation has received considerable interest recently, owing to the environmental concerns regarding fossil fuels and carbon emissions. Bacteria have a high growth rate during cultivation, making them promising for use in microbial fuel cells (MFCs). Using cell-imprinted polymers (CIPs) to enhance microbial binding to the anode is a promising approach; furthermore, elucidating both the synthesis techniques and recognition capabilities of cell-imprinted polymers is also a priority concern in biotechnology. In this work, the anode of a microbial fuel cell was prepared using microcontact imprinting of a cast polymer film. Experimental results indicate that the imprinting polymer solution concentration correlates with the adsorption of bacteria to the finished film. The morphologies of the imprinted cavities, and the distribution of Rhodobacter sphaeroide on the Rhodobacter sphaeroide-imprinted polymers (RsIPs) was monitored by scanning electron mi...

Fluidized capacitive bioanode as a novel reactor concept for the microbial fuel cell.

The use of granular electrodes in Microbial Fuel Cells (MFCs) is attractive because granules provide a cost-effective way to create a high electrode surface area, which is essential to achieve high current and power densities. Here, we show a novel reactor design based on capacitive granules: the fluidized capacitive bioanode. Activated carbon (AC) granules are colonized by electrochemically active microorganisms, which extract electrons from acetate and store the electrons in the granule. Electricity is harvested from the AC granules in an external discharge cell. We show a proof-of-principle of the fluidized capacitive system with a total anode volume of 2 L. After a start-up period of 100 days, the current increased from 0.56 A/m(2) with 100 g AC granules, to 0.99 A/m(2) with 150 g AC granules, to 1.3 A/m(2) with 200 g AC granules. Contact between moving AC granules and current collector was confirmed in a control experiment without biofilm. Contribution of an electro-active biofilm to the current density with recirculation of AC granules was limited. SEM images confirmed that a biofilm was present on the AC granules after operation in the fluidized capacitive system. Although current densities reported here need further improvement, the high surface area of the AC granules in combination with external discharge offers new and promising opportunities for scaling up MFCs.