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Electrodes are important components of bioelectrochemical systems (BESs), such as the microbial fuel cells (MFCs). The low-cost cathodes of titanium–nickel (Ti/Ni) and graphite felt-nickel (GF/Ni) are important to be evaluated as cathodes for MFCs. In this study, Ni particles are deposited onto the Ti and GF surface using a simple and low-cost electrodeposition technique. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to analyse the cathode surfaces. The electrodeposition of Ni onto GF appears more uniform without significant agglomeration compared with that onto Ti. This uniform deposition is perhaps the reason for a higher maximum power density ( P max ), lower internal resistance ( R in ) and higher Columbic efficiency ( CE ) for MFC with GF/Ni cathode (113.4 ± 0.6 mW/m 2 , 1264.4 Ω and 29.6%, respectively) than those measured with Ti/Ni cathode (110.7 ± 8.0 mW/m 2 , 3375.8 Ω and 23.7%, respectively). However, the performance of these cathodes remains lower compared with the GF/Pt cathode (140.0 mW/m 2 , 845.7 Ω and 42.0%, respectively). Based on the preparation technique, material cost and performance, both Ti/Ni and GF/Ni cathodes can be considered as alternative to Pt catalyst for MFC application. [ABSTRACT FROM AUTHOR]

Ceramic membranes (CMs) with different pore sizes (0.14 μm CM1, 150 kDa CM2 and 5 kDa CM3) were tested as separators in two-chamber microbial fuel cells (MFCs). The performance and ionic gradient concentration of MFCs using CMs were compared with that of cation exchange membrane (CEM), Nafion 117. MFC with CMs exhibited a higher performance than that of CEM under batch operation. The highest power density of 1790 ± 60 mW/m 2 , columbic efficiency (CE) of 41 ± 10% and internal resistance of 102 ± 13 Ω were obtained for MFC with CM3 under batch mode operation. The highest power density, columbic efficiency and internal resistance of MFC with CEM were found to be 1225 ± 20 mW/m 2 , 21 ± 1% and 400 ± 10 Ω, respectively. The highest performance of MFC with CM3 was expected due to a higher porosity of CM3 (13.8%) compared with that of CM1 (11.0%) and CM2 (11.05%). MFCs operated with catholyte containing salt solution, phosphate buffer basal medium without carbon source and yeast extract (PBBM-SA), generated lower current than with phosphate buffer (PB) as catholyte. This difference was more significant in the MFCs with the CEM Nafion 117 than with ceramic membranes. The non-selective porous ceramic membranes improved the diffusion of protons in the presence of other high concentration cations and resulted in MFC with higher performance. Hence, the porous ceramic membrane is a potential candidate separator for the development of commercial scale MFCs. [ABSTRACT FROM AUTHOR]

In this study, a single layer graphene oxide is successfully synthesized and used as a nano-filler in a self-fabricated sulfonated polyether ether ketone (SPEEK) to make a composite proton exchange membrane, graphene oxide/SPEEK (GO-SPEEK). The properties of GO-SPEEK, Nafion ® 117 and SPEEK are then compared to ascertain their selectivity to proton transport compared to both water and oxygen. GO-SPEEK was found to have the highest selectivity with a water uptake of 85.4%, proton conductivity of 1.48 × 10 −3 S cm −1 and oxygen diffusion coefficient of 1.154 × 10 −6 cm 2 s −1 . During tests in Microbial Fuel Cells (MFCs), the MFC system with Nafion ® 117 membrane produces the highest maximum power density (1013 mW m −2 ) followed by the MFCs with GO-SPEEK (902 mW m -2 ) and SPEEK (812 mW m −2 ) membranes. On the other hand, the MFC with GO-SPEEK membrane produces the highest coulombic efficiency (16.88%). The high efficiency and comparable maximum power density which is produced by the MFC with GO-SPEEK membrane, shows that GO-SPEEK membrane is a promising alternative membrane to replace the expensive Nafion ® 117 as a separator in the MFC. [ABSTRACT FROM AUTHOR]

BACKGROUND Sulfonated poly (ether ether ketone) ( SPEEK) membranes and their modifications are viewed as arguably the most promising in microbial fuel cell (MFC) applications due to their non-fluorinated base, superior chemical stability, and lower costs compared with Nafion membranes. In this work, SPEEK membranes with different degrees of sulfonation ( DSs) (60% to 76%) and blended with charged surface modifying macromolecule (cSMM) were used as electrolytes in an MFC for simultaneous electricity generation and wastewater treatment. RESULTS Performance evaluation of newly fabricated membranes was carried out and was compared with that of Nafion 117. The MFC with SPEEK76/cSMM generated about 16.5% higher maximum power density (172.1 mW m−2) than that with Nafion 117 (143.7 mW m−2). In addition, the SPEEK76/ cSMM exhibited the highest coulombic efficiency (CE) of 17.6%, which was 21.6% higher than that of Nafion 117 (13.8%). Chemical oxygen demand ( COD) removal of all characterized membranes was above 80% in our particular MFC. CONCLUSION MFC is a suitable method for simultaneous wastewater treatment and electricity generation. SPEEK76/ cSMM is a promising membrane to be applied in MFC. © 2014 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Abstract: Oxygen Reduction Reactions (ORR) are one of the main factors of major potential loss in low temperature fuel cells, such as microbial fuel cells and proton exchange membrane fuel cells. Various studies in the past decade have focused on determining a method to reduce the over potential of ORR and to replace the conventional costly Pt catalyst in both types of fuel cells. This review outlines important classes of abiotic catalysts and biocatalysts as electrochemical oxygen reduction reaction catalysts in microbial fuel cells. It was shown that manganese oxide and metal macrocycle compounds are good candidates for Pt catalyst replacements due to their high catalytic activity. Moreover, nitrogen doped nanocarbon material and electroconductive polymers are proven to have electrocatalytic activity, but further optimization is required if they are to replace Pt catalysts. A more interesting alternative is the use of bacteria as a biocatalyst in biocathodes, where the ORR is facilitated by bacterial metabolism within the biofilm formed on the cathode. More fundamental work is needed to understand the factors affecting the performance of the biocathode in order to improve the performance of the microbial fuel cells. [Copyright &y& Elsevier]

SUMMARY Polyaniline (Pani), vanadium oxide (V2O5), and Pani/V2O5 nanocomposite were fabricated and applied as a cathode catalyst in Microbial Fuel Cell (MFC) as an alternative to Pt (Platinum), which is a commonly used expensive cathode catalyst. The cathode catalysts were characterized using Cyclic Voltammetry and Linear Sweep Voltammetry to determine their oxygen reduction activity; furthermore, their structures were observed by X-ray Diffraction, X-ray Photoelectron Spectroscopy, Brunauer-Emmett-Teller, and Field-Emission Scanning Electron Microscopy. The results showed that Pani/V2O5 produced a power density of 79.26 mW/m2, which is higher than V2O5 by 65.31 mW/m2 and Pani by 42.4 mW/m2. Furthermore, the Coulombic Efficiency of the system using Pani/V2O5 (16%) was higher than V2O5 and Pani by 9.2 and 5.5%, respectively. Pani-V2O5 also produced approximately 10% more power than Pt, the best and most common cathode catalyst. It declares that Pani-V2O5 can be a suitable alternative for application in a MFC system. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: The microbial fuel cell (MFC) is a very promising technology for generating electrical energy from anaerobic fermentation of organic and inorganic matter in wastewater using microorganisms as biocatalysts while simultaneously treating the wastewater. However, the overall low performance of the MFC compared to other more established fuel cell technologies and the high cost of its components compared to the low value of the wastewater it treated, are the two major barriers to commercialization. In recent years, MFC’s performance has been improved by using among other things, cheaper nano-composite materials such as nano-structured carbon in the electrodes that are more conductive and mechanically stabile with larger surface area and higher electrochemical catalytic activity compared to the conventional Pt on carbon. However, the nano-structured carbon electrodes have also been reported to have some serious drawbacks such as toxicity to the microbial consortium in the biofilm attached on its surface, which reduces performance of the MFC. This paper tries to highlight the broad-spectrum of different nano-composite materials that have been used as electrode material in the MFC in recent years. [Copyright &y& Elsevier]

Abstract: The urgent need to address the twin problems of the modern world, energy insecurity caused by fossil fuel depletion and climate change caused by global warming from carbon dioxide emission and the greenhouse effect has led to among other things the emergence of fuel cell technology as a green energy technology that could generate cleaner and highly efficient energy. Microbial fuel cell (MFC), an emerging dual function, bioenergy conversion device, that not only treats wastewater but also generates electricity, has caught much attention of both fuel cell and bioenergy researchers. Until today, the commercialization of MFC has been restricted mainly due to its high cost and low power density. Many challenges still remain to be conquered, in order to improve the performance and commercialization of MFC. It is generally known that ion exchange membrane in MFC is one of the main factors that could significantly affect the cost and performance of MFC. This review provides an overview of several important membrane characteristics, which include membrane internal resistance, membrane biofouling, pH splitting, oxygen diffusion, and substrate loss across the membrane. The negative impact of these characteristics on MFC performance, are discussed. Moreover, this review concerns the types of membrane that have been applied in MFC systems, such as cation exchange membranes, anion exchange membranes, membraneless technology, polymer/composite membranes, and porous membranes. The future trend of membrane development for MFC applications is also discussed. [Copyright &y& Elsevier]

Abstract: Anode materials are important in the power generation of microbial fuel cell. In this study, polyaniline was used as a conducting polymer anode in two chambers MFC. XPS and SEM were used for the characterization of functional groups of anode materials and the morphology. The power generation of microbial fuel cell was elevated by the modification of anode by nitric acid, ethylenediamine, and diethanolamine. The time that MFC reaches its maximum power generation was shortened by modification. Moreover the SEM photos prove that, it causes better attachment of microorganisms as biocatalysts on electrode surface. The best performance of among the MFCs with different anode electrodes, was the system working by polyaniline modified by ethylenediamine as that generated power of 136.2 mW/m2 with a 21.3% Coulombic efficiency. [Copyright &y& Elsevier]

A novel nano-bio composite polypyrrole (PPy)/kappa-carrageenan(KC) was fabricated and characterized for application as a cathode catalyst in a microbial fuel cell (MFC). High resolution SEM and TEM verified the bud-like shape and uniform distribution of the PPy in the KC matrix. X-ray diffraction (XRD) has approved the amorphous structure of the PPy/KC as well. The PPy/KC nano-bio composites were then studied as an electrode material, due to their oxygen reduction reaction (ORR) ability as the cathode catalyst in the MFC and the results were compared with platinum (Pt) as the most common cathode catalyst. The produced power density of the PPy/KC was 72.1 mW/m 2 while it was 46.8 mW/m 2 and 28.8 mW/m 2 for KC and PPy individually. The efficiency of the PPy/KC electrode system is slightly lower than a Pt electrode (79.9 mW/m 2 ) but due to the high cost of Pt electrodes, the PPy/KC electrode system has potential to be an alternative electrode system for MFCs. [ABSTRACT FROM AUTHOR]

Highlights: [•] Serial and parallel circuits of single MFC units increased overall performance. [•] The maximum generated voltage of MFC stack was 2.042V. [•] Lowest internal resistance was achieved via parallel connection of three substrates in 20gl−1. [•] Maximum generated power and current by stack were 109.45mWm−2and 98.14mAm−2, respectively. [Copyright &y& Elsevier]

Abstract: Microbial fuel cells (MFCs) hold great promise as an alternative for direct biochemical energy extraction from both biomass and wastewater. However, the commercialization and scaling-up of MFCs is not completely feasible, due to the high price of platinum (Pt) as a cathode catalyst. In this paper, we studied the use of a carbon nanotube (CNT) composite catalyst, to reduce the amount of Pt (without decline of efficiency) for moving towards the commercialization of MFCs. CNT/Pt composite electrodes would increase MFC power output by 8.7–32.2%; with respect to the pristine Pt as a catalyst for the cathode at a chemical oxygen demand (COD) substrate of 100mg/l and 2000mg/l, respectively. Moreover, the amount of Pt in the CNT/Pt electrode could be reduced by up to 25% of the amount necessary for a conventional Pt/carbon electrode. [Copyright &y& Elsevier]

Abstract: In this study, self-made carbon nanofiber (CNF)/Nafion and activated carbon nanofiber (ACNF)/Nafion nanocomposite membranes are fabricated and tested in a microbial fuel cell. The data are compared with Nafion 117 as a common membrane in MFCs and Nafion 112. The electrospinning method was used for the production of CNFs. This method is chosen because it is simple, highly cost effective, and the most prolific method of all that could be used to produce CNF. Nanocomposite membranes are used because they had higher production power and coulombic efficiency (CE) than Nafion 117 and Nafion 112 in MFC systems. The results reveal that the system is operated by the ACNF/Nafion membrane produce the highest voltage of 57.64mWm−2, while Nafion 112 produces the lowest power density (13.99mWm−2). [Copyright &y& Elsevier]