Characterization of Fe/N-doped graphene as air-cathode catalyst in microbial fuel cells

This work proposed a simple and efficient approach for synthesis of durable and efficient non-precious metal oxygen reduction reaction(ORR) electro-catalysts in MFCs. The rod-like carbon nanotubes(CNTs)were formed on the Fe–N/SLG sheets after a carbonization process. The maximum power density of1210 ± 23 m W·m~(-2) obtained with Fe–N/SLG catalyst in an MFC was 10.7% higher than that of Pt/C catalyst(1080 ± 20 mW ·m~(-2)) under the same condition. The results of RDE test show that the ORR electron transfer number of Fe–N/SLG was 3.91 ± 0.02, which suggested that ORR catalysis proceeds through a four-electron pathway. The whole time of the synthesis of electro-catalysts is about 10 h, making the research take a solid step in the MFC expansion due to its low-cost, high efficiency and favorable electrochemical performance. Besides, we compared the electrochemical properties of catalysts using SLG, high conductivity graphene(HCG, a kind of multilayer graphene) and high activity graphene(HAG, a kind of GO) under the same conditions, providing a solution for optimal selection of cathode catalyst in MFCs.The morphology, crystalline structure, elemental composition and ORR activity of these three kinds of Fe–N/C catalysts were characterized. Their ORR activities were compared with commercial Pt/C catalyst.It demonstrates that this kind of Fe–N/SLG can be a type of promising highly efficient catalyst and could enhance ORR performance of MFCs.     

Effect of electrolyte pH on the rate of the anodic and cathodic reactions in an air-cathode microbial fuel cell

The measurement of electricity generation from an air-cathode microbial fuel cell (MFC) with a mixed bacteria culture at different pH showed that this MFC could tolerate an initial (feed solution) pH as high as 10. The optimal initial pH was between 8 and 10 with higher current generation compared to lower or higher pH. The bacterial metabolism exhibited a buffer effect and changed the electrolyte pH. The impedance spectra of the anode and cathode of the MFC at the open-circuit potential (OCP) revealed that the anodic microbial process preferred a neutral pH and microbial activities decreased at higher or lower pH; while the cathodic reaction was improved with increasing pH.     

Nanostructured polyaniline-coated anode for improving microbial fuel cell power output

An approach for improving the power generation of a dual-chamber microbial fuel cell by using a nanostructured polyaniline (PANI)-modified glassy carbon anode was investigated. Modification of the glassy carbon anode was achieved by the electrochemical polymerisation of aniline in 1 M H₂SO₄ solution. The MFC reactor showed power densities of 0.082 mW cm^?2 and 0.031 mW cm^?2 for the nano- and microstructured PANI anode, respectively. The results from electron microscopy scanning confirmed formation of the nanostructured PANI film on the anode surface and the results from electrochemical experiments confirmed that the electrochemical activity of the anode was significantly enhanced after modification by nanostructured PANI. Electrochemical impedance spectroscopic results proved that the charge transfer would be facilitated after anode modification with nanostructured PANI.     

Membrane fluidity sensoring microbial fuel cell

A study has been performed to examine the effect of temperature and ethanolic stresses on the coulombic efficiency of a microbial fuel cell. The conventional-type fuel cell containing Gram-negative bacteria, Proteus vulgaris, was investigated as a model system. From current output measurements, it was found that the coulombic yields were altered by environmental stresses such as temperature shock or ethanol treatment to the bacteria. While high-temperature or ethanolic shock led to a remarkable decrement in coulombic output, the low-temperature shock induced a slight increase in microbial fuel cell efficiency. These results indicate that the membrane fluidity is affected considerably by environmental stress, which in turn affects the electron transfer process through the bacterial cell membrane to and from the electrode. This interpretation was confirmed by the cyclic voltammetric study of a mediator on an electrode surface modified with the lipids extracted from the membrane of P. vulgaris under the given stress. Markedly different electrochemical behaviors were observed depending on the environmental stress. A reciprocal relationship between coulomb output and the ratio of saturation/unsaturation of fatty acids has been observed. This is the first report, to our knowledge, that the structural adaptation of membrane fatty acids in response to the environmental shock can regulate the coulombic efficiency of a microbial fuel cell.     

Supercapacitive operational mode in microbial fuel cell

Supercapacitive microbial fuel cells (SC-MFCs) are an emerging and promising field that has captured the attention of scientists in the past few years. This hybridization consists in the integration of supercapacitive features in the MFC electrodes to boost the performance output. The MFC anaerobic and aerobic enviroments induce self-polarization of the electrodes. The electrodes can be discharged galvanostatically and then self-recharged by the biotic/abiotic environments. During the discharge, two main phenomena named electrostatic and faradaic take place but the separation and quantification of the two contributes seems to be challenging. Galvanostatic discharges of SC-MFC produce at least one order of magnitude higher current/power compared with continuous operations, making it promising for pulsed type applications.     

Self-powered ultrasensitive nanowire photodetector driven by a hybridized microbial fuel cell

An integrated system consisting of a carbon fiber-ZnO hybrid nanowire (NW) multicolor photodetector is driven by a microbial fuel cell (see picture; PMMA = poly(methyl methacrylate), E = electrode). The self-powered photodetector can detect at light levels of as little as nW?cm(-2) intensity with a responsivity of more than 300?A?W(-1).     

Recent advancements in real-world microbial fuel cell applications

This short review focuses on the recent developments of the Microbial Fuel Cell (MFC) technology, its scale-up and implementation in real world applications. Microbial Fuel Cells produce (bio)energy from waste streams, which can reduce environmental pollution, but also decrease the cost of the treatment. Although the technology is still considered “new”, it has a long history since its discovery, but it is only now that recent developments have allowed its implementation in real world settings, as a precursor to commercialisation.     

Electricity generation by an enriched phototrophic consortium in a microbial fuel cell

Microbial fuel cell (MFC) technology is a novel electricity generation process catalyzed by microorganisms. Much progress is made in the design and construction of MFCs, however the diversity of the electrochemically active microorganisms and the electricity generation mechanisms remain a black box. As sun is a predominantly unused energy resource, here we present a highly enriched phototrophic consortium that can produce electricity in an “H” typed MFC at a high power density (2650 mW m⁻², normalized to membrane area) in light, which was eightfold of that produced by non-enriched consortium in the same reactor. Light–dark shift experiments showed that light contributed to the electricity generation. A microbial excreted mediator assisted the electron transfer to the electrode. During the experiment, the accumulation of the mediator over time enhanced the electron transfer rate. The excitation–emission matrix fluorescence spectroscopy results indicated indole group containing compound representing the dominant mediator component.     

Enhance cathodic capacitance to eliminate power overshoot in microbial fuel cells

Journal of Solid State Electrochemistry - Power overshoot that presents in the power curves of microbial fuel cells (MFCs) is one of the main reasons for the deterioration of MFC performance over...     

Electricity production of a microbial fuel cell stack integrated into a sink drain pipe

In this study, five two-chambered microbial fuel cells (MFCs) were hydraulically connected in series to constitute a MFC stack, which was integrated into a sink drain pipe for kitchen wastewater treatment. Performances of the MFC stack operating with artificial and real wastewater were studied. Considering the practical application, the voltage response to different flow rates and temperatures of the substrate was also investigated. It was found that the MFC stack could achieve a reasonable performance, with an average open circuit voltage of 3.44 ± 0.02 V, a peak power of 45.74 ± 1.39 mW (i.e. 809.27 mW/m²) and a coulombic efficiency of 78.2 ± 3.6 %. The MFC performance was disturbed by the flushing process, but could recover after a few minutes. The results also suggest that the MFC stack can operate after flushing by the substrate at 50 °C, above which irreversible performance deterioration was observed. The proposed MFC stack is expected to serve as a potential power source for lighting and low-power devices, especially in off-grid rural areas.     

Optimization for the improvement of power in equal volume of single chamber microbial fuel cell using dairy wastewater

Microbial fuel cells (MFCs) are a type of sustainable technology that may treat wastewater and generate power at the same time. Therefore, researchers are being challenged to design a technically feasible bio electrochemical system that generates environmentally friendly and renewable electricity from waste water. The current research examined at how MFC may be used to generate electricity while treating real dairy wastewater (RDW) with Pseudomonas aeruginosa-MTCC-7814. The experiments were carried out in fed-batch mode for 15 days in two 300 ml single chamber microbial fuel cells (SCMFCs) that were connected in series. During a fed batch investigation, three process parameters such as inoculum percentage, temperature, and pH were optimized. Inoculum percentage, temperature, and pH were found to be optimal at 5%, 37 °C, and 7.4, respectively and the highest open-circuit voltage was found to be 1025 mV. The COD removal efficiency and columbic efficiency (CE) were found to be 95.84% and 37.13% respectively. The optimized fed batch process yielded the maximum current density and power density of 313 mA/m² and 105 mW/m², respectively. Thus, this work successfully demonstrates that connecting single chamber microbial fuel cells (SCMFCs) in series is a viable technique for generating sustainable power utilizing Pseudomonas aeruginosa-MTCC-7814 from dairy wastewater.     

Simultaneous processes of electricity generation and p-nitrophenol degradation in a microbial fuel cell

This study initially demonstrates that the electricity generated by a microbial fuel cell (MFC) can be used to in situ generate H₂O₂ at a carbon felt cathode. In the presence of scrap iron, H₂O₂ further reacts with Fe²⁺ to produce hydroxyl radicals. Attributed to the oxidation of H₂O₂ and hydroxyl radicals, and the oxidation–reduction of scrap iron, p-nitrophenol was significantly removed in the cathode chamber of the MFC. The p-nitrophenol was completely degraded after 12 h, and about 85% of TOC was removed after 96 h. Simultaneously, a maximum power density (143 mW m^?2) was generated by the MFC. It is concluded that a MFC not only can generate electricity and degrade biodegradable compounds, but also remove bio-refractory pollutants.     

Improved performance of anode with iron/sulfur-modified graphite in microbial fuel cell

The paper reports the operation of a new-design microbial fuel cell using compost leachate as a substrate, oxygen/electrodeposited MnO_x cathode and a new-anode concept with graphite modified by an iron/sulfur solid chemical catalyst which almost eliminates the starting delay time and gives very high current and power densities, I ~ 25 A m^− 3 at P_max ~ 12 W m^− 3 or I ~ 3.8 A m^− 2 at P_max ~ 1.8 W m^− 2.     

Enhanced electricity production from microbial fuel cells with plasma-modified carbon paper anode

Microbial fuel cells (MFC) provide a new opportunity for simultaneous electricity generation and waste treatment. An improvement in the anode capacity of MFCs is essential for their scale-up and commercialization. In this work we demonstrate, for the first time, that plasma-based ion implantation could be used as an effective approach to modify carbon paper as an anode for MFC to improve its electricity-generating capacity. After the N(+) ion implantation, a decreased charge-transfer resistance is achieved, which is attributed to the increased C-N bonds after N(+) ion implantation. In addition, the surface roughness and hydrophobicity are also changed, which favor microbial adhesion on the anode surface. The cyclic voltammetry results show that both the electrochemical activity and the electron transfer are enhanced remarkably, leading to better MFC performance compared to the control. Such a plasma surface modification technique provides an effective way to modify the electrode for enhancing MFC performance for power generation.     

Preparation,characterization, and optimization of a porous polyaniline-copper anode microbial fuel cell

Journal of Solid State Electrochemistry - In this paper, we report on the development and optimization of a copper anode material coated with a thin polyaniline layer for use in a microbial fuel...     

Recent advances in osmotic microbial fuel cell technology: A review

Integration of Forward Osmosis (FO) and Microbial Fuel Cell (MFC) technology is called Osmotic Microbial Fuel Cell (OMFC). It has several advantages, including improved performance in electricity generation and drinking water recovery compared to MFC. Making OMFC efficient for treatment and resource recovery, basic concepts of MFC and FO must be properly understood and implemented. Various researchers have focused on its components, degradation of wastewater, electron and proton transport mechanism, designs, the role of draw solution, etc. Recent publications have also shown growth in FO membrane composition and OMFC design. Utilizations of an efficient draw solution for better compatibility of anodic bacteria along with its recovery are also a big challenge. The aim of this review paper is to compile all the scattered information on the above aspects and present it in a more logical way in one place for the easy understanding of researchers. The paper also focuses on encouraging OMFC technology for commercial use by developing cost-effective FO membranes and electrodes, improving bacterial metabolic activity for energy production, and enhancing draw solution and cost-effective draw solution recovery methods. Therefore, OMFC technology seems the ultimate solution for wastewater treatment, electricity generation, and freshwater recovery in the coming future.     

Power generation using an activated carbon and metal mesh cathode in a microbial fuel cell

An inexpensive activated carbon (AC) air cathode was developed as an alternative to a platinum-catalyzed electrode for oxygen reduction in a microbial fuel cell (MFC). AC was cold-pressed with a polytetrafluoroethylene (PTFE) binder to form the cathode around a Ni mesh current collector. This cathode construction avoided the need for carbon cloth or a metal catalyst, and produced a cathode with high activity for oxygen reduction at typical MFC current densities. Tests with the AC cathode produced a maximum power density of 1220 mW/m² (normalized to cathode projected surface area; 36 W/m³ based on liquid volume) compared to 1060 mW/m² obtained by Pt catalyzed carbon cloth cathode. The Coulombic efficiency ranged from 15% to 55%. These findings show that AC is a cost-effective material for achieving useful rates of oxygen reduction in air cathode MFCs.