Performances Of Microbial Fuel Cells Research Articles

Construction of double tube granular sludge microbial fuel cell and its characteristics and mechanism of azo dye degradation.

Microbial fuel cells (MFCs) can obtain electrical energy from extensive organic matter and complete wastewater treatment at the same time. The principal purpose of the research is to find a solution to the biodegradation of X-3B in a double tube MFC with graphite fiber brush as the anode and carbon cloth as the cathode. The anaerobic, aerobic, and electrochemical processes in the MFC were investigated. The effects of dye concentration and circuit connectivity on the performances of MFCs were explored. The degradation efficiency of X-3B in the anode region (85.56%) was higher than that in the cathode region (14.16%) within 24h under the optimal voltage of 0.43V, indicating a synergistic effect between electrode reaction and biodegradation. The power density increased from 12.12 mW/m3 to 60.45 mW/m3 with the addition of X-3B from 50 to 200mg/L, because of the reduced ohmic and polarization resistance. Intermediate productions such as aniline were manufactured with the conjugated double bond of X-3B broken, and the intermediates were degraded into small molecular products like phenol during further degradation processes. Moreover, dye concentration and circuit connection had significant effects on the relative abundance of the microbial community at phylum and genus levels. In general, MFC is a good approach to energy generation and azo dye treatment at the same time.

Electrochemical and microbiological insights into the use of 1,4-diazabicyclo[2.2.2]octane-functionalized anion exchange membrane in microbial fuel cell: A benchmarking study with Nafion

In this work, two polymeric membrane separators (a proton exchange membrane (PEM), Nafion, and an anion-exchange membrane (AEM), 1,4-diazabicyclo[2.2.2]octane (DABCO)-functionalized PSEBS) deployed in microbial fuel cells (MFCs) are comparatively assessed. The performances of MFCs according to membrane type were evaluated by biological and electrochemical techniques, employing metagenomics, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). It was found that the anodic biofilms of MFCs, irrespective of the type of membrane, were dominated by Geobacter sulfurreducens (37 and 50% for AEM-MFC and PEM-MFC, respectively), a well-known electrochemically active species. Furthermore, the AEM-MFC reflected a significantly lower internal resistance (145 Ω) compared to PEM-MFC (339 Ω) and produced higher maximal current densities and energy yields at all substrate (acetate) concentrations, as follows: 400 vs. 285 mA m−2 (5 mM acetate); 360 vs. 320 mA m−2 (10 mM acetate), 305 vs. 235 mA m−2 (15 mM acetate) and 238 vs.132 kJ m−2 gCOD (5 mM acetate), 161 vs. 128 kJ m−2 gCOD (10 mM acetate), 114 vs. 59 kJ m−2 gCOD (15 mM acetate) respectively. The CV measurements implied diffusion limitations in the MFCs, which were supported by EIS. In addition, the PEM and AEM characterizations revealed that in both cases, the ion exchange capacity, ionic conductivity and oxygen mass transport features were altered considerably over the 39 days during which the MFCs operated.

Deciphering electron-shuttling characteristics of epinephrine and dopamine for bioenergy extraction using microbial fuel cells

This first-attempt study provided novel electrochemical exploration via microbial fuel cells (MFCs), suggesting why catecholamine hormone-neurotransmitters epinephrine (EP) and dopamine (DA) could effectively trigger acute stress responses for humans. According to bioelectrochemical engineering, EP and DA are ortho-diphydroxyl (o-diOH) substituent(s)-bearing electron shuttles (ESs) that could effectively mediate electron-transfer capabilities for bioenergy extraction. This study quantitatively compared redox-mediating characteristics of EP and DA with other antioxidants and ESs, suggesting possible mechanisms of bioenergy-driven responses to organisms. Although some electrochemical activities of EP and DA were characterized in medical literature, this work clarified that EP and DA were also electrochemically favorable ESs for efficient bioenergy extraction. Compared to vitamin B2 (VB), vitamin C (VC) and gallic acid (GA), quantitative evaluation upon bioenergy-stimulating capabilities of EP and DA were clearly revealed via MFC modules. Apparently, both EP and DA as ESs significantly exhibited stable and reversible redox potential peaks in cyclic voltammetry. Evidently, power density performances of MFCs supplemented with EP and DA considerably increased ca. 127–385%, suggesting that DA and EP would be the most appropriate ESs to effectively stimulate electron-mediating capabilities in multicellular organisms. It was also suspected that highly efficient power-stimulating capabilities of DA and EP could be strongly associated with their electrochemically-steered disease-curative and life-threatening capabilities to humans.

N-doped carbon nanofibers as catalyst layer at cathode in single chamber Microbial Fuel Cells

Overall performances of Single Chamber Microbial Fuel Cells (SCMFCs) with air-cathode are extremely improved by optimizing a cathodic catalyst not containing metals. To reach this goal, the main target is based on design nitrogen doped carbon-based nanofibers (N-CNFs) as catalyst layer at the cathode. The fine-tuning of the electrochemical properties of CNFs plays a key role to grant the direct oxygen reduction reaction (ORR). A pyrolysis treatment, conducted under inert atmosphere at 900 °C, is carried out to obtain a self-induced nitrogen doping in the carbon nanofibers during carbonization step, ensuring a proper value of electrical conductivity. The resulting N-CNFs, thanks to their content of nitrogen defects together with their high surface area, result to be a promising catalyst layer for the ORR. Physical, chemical and morphological properties of nanofibers are investigated, demonstrating the presence of N-doped graphitic sheets in the nanofiber mats. In particular, the key role of graphitic and pyridinic nitrogen related to the improvement of electrochemical behaviour of N-CNFs, is explained. All these features enhance the overall performance of SCMFCs. Indeed, SCMFCs with N-CNFs catalyst cathode reach a maximum power output comparable to that obtained by Pt based cathodes. The impressive result is strictly due to the important features of N-CNFs.

Boosted activity of graphene encapsulated CoFe alloys by blending with activated carbon for oxygen reduction reaction

The slow oxygen reduction reaction (ORR) hampers the efficiency of microbial fuel cells (MFCs) to a large extent, which usually requires catalysts to facilitate the electron transfer. The major challenge of the existed non-precious metals in place of the noble metal catalysts (Pt, Pd, Au et al.) for ORR is their low efficiency, which urgently needs special route to tackle this issue. Herein, we report a simple and convenient technique using prussian blue analogues as precursor to directly synthesize the N-doped graphene encapsulated CoFe alloy which is present in “Core-Shell” structure via calcination of Co2Fe(CN)6 in inert condition. The encapsulation of metal alloy within graphene shell immensely promotes the electron transfer from the encapsulated metals to the graphene surface. It efficiently optimizes the electronic structure of the as-synthesized catalyst and thereby triggers high ORR activity. The surrounding activated carbon (AC) contributes to the large pore structure and further offers a commodious route for the oxygen to gain electron. Therefore, the total resistance of air cathodes is significantly reduced from 17.300 Ω to 9.551 Ω and the electrochemical activity is greatly improved. The power performances of MFCs indicate that CoFe/C-10% presents the highest maximum power density (MPD) of 1616 mW m−2, which is 5 times larger than that of the bare AC. It is well concluded that the graphene encapsulated CoFe alloy can be recognized as potential ORR catalyst for MFCs.

3D printed porous carbon anode for enhanced power generation in microbial fuel cell

3D porous carbon structures, fabricated via 3D printing technique, were first utilized as the anode materials for microbial fuel cells (MFCs). The intrinsic biocompatibility of 3D printed carbon anodes, together with the open porous structures, greatly enhanced the metabolic activities of microorganisms. The secondary 3D roughness generated from carbon formation functioned as an ideal support for microbial growth, which further increased the surface area of anodes as well. All these factors together determined the exclusive electrochemical performances of MFCs for enhanced power generation and scaling up application. Through carefully tuning the carbonization processes, a multiscale 3D porous carbon structure was achieved for bacterial growth and mass transfer, leading to the highest maximum output voltage, open circuit potential (OCP) and power density for a 300µm porosity (453.4 ± 6.5mV, 1256 ± 69.9mV and 233.5 ± 11.6mWm−2, respectively). Such performance is superior to that of carbon cloth anode and carbon fiber brush anode under the same condition.

Enhanced Bioelectrocatalysis of Shewanella oneidensis MR-1 by a Naphthoquinone Redox Polymer

Shewanella oneidensis MR-1 is the model organism used in microbial fuel cells (MFCs). A great deal of research has focused on this bacterium to improve extracellular electron transfer (EET) and subsequently the power output in MFCs. Here, we report on the enhanced bioelectrocatalysis of S. oneidensis MR-1 by using a naphthoquinone redox polymer (NQ-LPEI) on a modified carbon felt electrode. A maximum anodic current of 3.70 ± 0.40 A m–2 is obtained in a three-electrode setup, a value 15 times higher than that obtained for an anode that did not contain the NQ-LPEI redox polymer (0.24 ± 0.05 A m–2). Additionally, a maximum power output of 0.53 ± 0.02 W m–2 was obtained in single-chamber MFCs where the NQ-LPEI modified anode was utilized. The power output was significantly higher than that obtained for MFCs with unmodified anodes (0.19 ± 0.05 W m–2). These findings suggest that NQ-LPEI could be used with known electrogenic microorganisms to further improve the performances of MFCs.

Comprehensive evaluation of two different inoculums in MFC with a new tin‐coated copper mesh anode electrode for producing electricity from a cottonseed oil industry effluent

We evaluated a new electrode material for its capacity to generate electricity by using a cottonseed effluent in two microbial fuel cells (MFCs). Tin‐coated copper (Sn‐coating Cu) mesh and platinum‐coated titanium were used as anode and cathode electrode materials, respectively. For a startup period that allowed slow‐growing electro‐active bacteria to form biofilms on the anode electrode, inoculums were supplied from anaerobic digester sludge (ADS) and estuary sediment (ES). The ADS‐inoculated MFC successfully achieved maximum power density of 160 mW/m2, whereas ES‐inoculated MFC had a maximum power density of 59 mW/m2. Maximum columbic efficiencies for ADS and ES were 12.8% and 5.6% and the corresponding COD removal efficiencies were 66.6% and 53.6%, respectively. A PCR‐DGGE analysis showed that the anode surface in ADS‐inoculated MFC has more groups of bacteria than that in ES‐inoculated MFC. The kinetic performances of MFCs evaluated by using the Nernst–Monod equation showed that maximum current density (Jmax) increased to around 1.62 A/m2 in the ADS‐inoculated MFC and 1.06 A/m2 in the ES‐inoculated MFC. © 2015 American Institute of Chemical Engineers Environ Prog, 35: 110–116, 2016

Microbial Fuel Cells in Waste Treatment: Recent Advances

The increasing awareness that there are limits to the availability of nonrenewable resources, as well as that there are limits to the biosphere’s ability to absorb wastes, are at the basis of the growing interest about Microbial Fuel Cells (MFCs) technology, with particular regards to their application to wastes treatment. MFCs, in fact, couple the direct electric power production to the degradation of organic compounds, liquid and solid wastes included. From municipal wastewater, to landfill leachate and solid waste, the application of MFCs to waste treatment achieved important results both in COD removal and power output. Unlike traditional Fuel Cells (FC), MFCs don't require chemical catalysts neither high working temperatures. Moreover, there is no net production of CO2. In the course of 20 years, the performances of MFC increased significantly and scaled prototypes were realized. The constant progresses achieved make a wide-scale application of MFC to waste treatment more reliable.

Influence of substrate on electricity generation of Shewanella loihica PV-4 in microbial fuel cells.

BackgroundThe substrate, serving as carbon and energy source, is one of the major factors affecting the performance of microbial fuel cells (MFCs). We utilized BIOLOG system to rapidly screen substrates for electricigens, and further evaluated influence of these substrates on electricity generation of Shewanella loihica PV-4 in MFCs.ResultsThree of most favorable substrates (lactate acid, formic acid and cyclodextrin) with OD590/750 of 0.952, 0.880 and 0.849 as well as three of most unfavorable substrates (galactose, arabinose and glucose) with OD590/750 of 0.248, 0.137 and 0.119 were selected by BIOLOG system under aerobic conditions. The chronoamperometry results showed that MFCs fed with these substrates exhibited different current behaviors. Cyclic voltammograms results showed that arabinose, galactose and glucose promoted electron transfer from outer membrane c-Cyts of cells to the electrode surface. Lactic acid, formic acid and cyclodextrin produced lower quantity of electric charge of 10.13 C, 9.83 C and 10.10 C, the corresponding OD600 value was 0.180, 0.286 and 0.152 in BES; while galactose, arabinose and glucose generated higher quantity of electric charge of 12.34 C, 13.42 C and 17.45 C, and increased OD600 values were 0.338, 0.558 and 0.409 in BES. SEMs results showed that plenty of plump and stretched cells as well as appendages were observed when lactic acid, formic acid, and cyclodextrin were utilized as substrates, while sparse cells in short shape were obtained when galactose, arabinose and glucose were used as substrates.ConclusionsThese results suggest that substrate not only has important role in electrochemical performances of MFCs but also in biological properties of electricigens. Lactic acid, formic acid, and cyclodextrin beneficial for cell growth under aerobic conditions are unfavourable for planktonic cell growth and current generation under anaerobic conditions, while consumptions of galactose, arabinose and glucose adverse to cell growth under aerobic conditions are favourable for planktonic cell growth and current generation under anaerobic conditions due to the increase of cell numbers with more outer membrane c-Cyts transferring electrons between the electrode surface and cells.

The influence of microbial synergistic and antagonistic effects on the performance of refinery wastewater microbial fuel cells

This study provides a preliminary investigation of the synergistic and antagonistic effects of different microbial strains and their influence on electricity generation and wastewater treatment performances in microbial fuel cells (MFCs). Microbial metabolic characteristics of petroleum hydrocarbon pollutants are studied simultaneously to provide further insight into how microbial synergistic and antagonistic effects influence MFCs. We observed a synergistic effect between Paenibacillus sp. and Deinococcus sp. and an antagonistic effect between Microbacterium sp. and Paenibacillus sp. and Deinococcus sp. The microbial synergistic and antagonistic effects significantly influenced MFC performance directly. The best MFC performance was observed with Paenibacillus sp. + Deinococcus sp. due to their synergistic effect, where the power density output reached 102.93 mW m−3, and the oil removal rate was 85.56 ± 1.10%. However, the performances of MFCs inoculated with Microbacterium sp. were considerably poorer because of its antagonistic effect on the other microbial strains, where the lowest power density output was 24.93 mW m−3, and the oil removal rate was 65.88 ± 1.10%. The degradation characteristics of petroleum hydrocarbons differ between microbial strains; thus, the relative results can provide further insight into how microbial synergistic and antagonistic effects influence MFCs.

A comparison of bioelectricity in microbial fuel cells with aerobic and anaerobic anodes

Microbial fuel cells (MFCs) can, besides running on wastewater, also derive energy directly from certain aquatic plants. However, few studies have focussed on electricity generation using aerobic anodes. This study presents a comparison of the MFC performances of an anaerobic-anode MFC (ana-MFC) and an aerobic-anode MFC (aa-MFC), and shows their individual conditions for optimal operation. Results show that the maximum power density of 7.07±0.45 mW/m2 for the ana-MFC occurred at 500 Ω, whereas the aa-MFC had a maximum power density of 2.34±0.16 mW/m2 at 2200 Ω. The ana-MFC generally achieved high electricity generation, and the aa-MFC achieved relatively high electricity generation when fed with a diluted substrate. In the ana-MFC, the optimal substrate for electricity generation was glucose (fermentable substrate); however, glucose and acetic acid (non-fermentable substrate) were both suitable substrates for the aa-MFC. The optimal gas retention times of the ana-MFC and the aa-MFC were 9 and 120 s, respectively. This retention time is an important limiting factor of electricity generation for the ana-MFC. The aa-MFCs fed with different substrates exhibited non-significant differences between bacterial communities. We observed the relative diversities of bacterial communities in the ana-MFC fed with various substrates. The results of denaturing gradient gel electrophoresis analysis suggest that Ochrobactrum intermedium, Delftia acidovorans, and Citrobacter freundii may be potential electrogenic bacteria. To our knowledge, this is the first study comparing the MFC performances of anaerobic and aerobic anodes.

A review of cellulosic microbial fuel cells: Performance and challenges

Cellulosic biomass, in the form of lignocellulosic materials, is a renewable and readily accessible source of organic substrate for microbial fuel cells (MFCs). The performances of cellulosic MFCs were compared on a common basis and with respect to the properties of the different cellulosic substrate each utilized. Moreover, the different experimental design approaches employed to overcome performance limitations of cellulosic MFCs were evaluated. Comparison of the mean peak currents and mean peak power densities revealed that MFCs run on cellulose were electrically outperformed by those run on starch but not those run on chitin. It was further observed that coulombic efficiency, the measure of effective substrate utilization for current generation, was greatest for soluble polysaccharide substrates, whether starch or cellulose. For insoluble polysaccharide substrates, coulombic efficiency decreased as the degree of polymerization increased. These and other conclusions indicate that both substrate accessibility and effective substrate utilization are important factors for electrical performance of cellulosic MFCs. The evaluation exposes the need for more thorough and systematic design and analysis of MFC experiments employing cellulose and other polysaccharides as substrates.

Electrochemical surface modification of carbon mesh anode to improve the performance of air-cathode microbial fuel cells

A convenient and promising alternative to surface modification of carbon mesh anode was fulfilled by electrochemical oxidation in the electrolyte of nitric acid or ammonium nitrate at ambient temperature. It was confirmed that such an anode modification method was low cost and effective not only in improving the efficiency of power generation in microbial fuel cells (MFCs) for synthetic wastewater treatment, but also helping to reduce the period for MFCs start-up. The MFCs with anode modification in electrolyte of nitric acid performed the best, achieving a Coulombic efficiency enhancement of 71 %. As characterized, the electrochemical modification resulted in the decrease of the anode potential and internal resistance but the increase of current response and nitrogen-containing and oxygen-containing functional groups on the carbon surface, which might contribute to the enhancement on the performances of MFCs.

Electricity generation using eight amino acids by air–cathode microbial fuel cells

Eight kinds of amino acids including L-Serine (Ser), L-Asparagine (Asn), L-Asparticacid (Asp), L-Glutamicacid (Glu), DL-Alanine (Ala), L-lysine (Lys), L-Histidine (His) and L-Arginine (Arg) are tested as substrates of single-chambered air–cathode microbial fuel cells (MFCs) with domestic wastewater as inoculation. Their total organic carbon (TOC) concentrations in solution are standardized as 720mgL−1. Ser produces the highest power density of 768mWm−2 and Ala produces the lowest of 556mWm−2. The Coulombic efficiencies (CEs) vary from 13±3% (obtained with Arg) to 30±1% (obtained with Ala). The removal efficiencies of total nitrogen (TN) are from 55±5% (Asn) to 94±4% (Asp), which may be associated with CEs. Maximum voltage outputs and TOC concentrations of the substrates appear to satisfy the empirical Monod-type equation when the external resistance is 150Ω. The performances of MFCs are considered to relate to the molecular weights and structures of eight amino acids.

Electrical energy generation from a large number of microbial fuel cells operating at maximum power point electrical load

Microbial fuel cells (MFCs) convert organic matter into electrical power. For most applications, the electrical-load seen from the MFC can advantageously be controlled by a DC/DC inductive converter. Implementation of a so-called maximum power point tracking (MPPT) control permits to set the operating point of the MFC to optimize power harvesting whatever the actual load. This paper studies the electrical performances of MFCs under maximum power point (MPP) load conditions. Ten similar single-chamber 1.3L MFCs are constructed and simultaneously tested. For an identical amount of injected organic matter (1g of acetate), the “perturbation and observation” (P&O) algorithm achieves a best electrical energy production of 985J electrical power, corresponding to 8.6% global energy conversion efficiency (ECE). A novel algorithm that regulates MFC voltage to one-third its open-circuit voltage is introduced and compared to the state of the art P&O algorithm. It enables a best conversion efficiency of 7.7% and promises low-cost effective implementation in silicon DC/DC converters.

Anode modification by electrochemical oxidation: A new practical method to improve the performance of microbial fuel cells

Electrochemical oxidation as a convenient and effective method was established for anode modification to improve the performance of microbial fuel cells (MFCs). The anode modification was realized by one-step electrochemical treatment in one of the three electrolytes (nitric acid, ammonium nitrate, ammonium persulfate) at ambient temperature. The performances of MFCs before and after anode modification were compared, confirming that all these anode modifications posed positive effects. The maximum power density of the MFC with the anode modified by nitric acid was 792 mW/m 2, which was 43% larger than the unmodified control (552 mW/m 2). Furthermore, the Coulombic efficiency (CE) significantly promoted about 71% from 14% (the unmodified MFC) to 24%. It revealed that the electrochemical oxidation resulted in the change of the anode properties, such as surface morphology, internal resistance and anode potential, and thus benefited to the microbial attachment and electron transfer on the anode surface, which might contribute to the performance improvement of the MFCs.