Increasing power generation of microbial fuel cells with a nano-CeO2 modified anode

Nano-CeO₂ was used to modify the carbon felt anode in microbial fuel cell (MFC). The MFC with the modified anode obtained the higher closed circuit voltage resulting from the lower anode potential, the higher maximum power density (2.94 W m^?2), and the lower internal resistance (77.1 Ω). Cyclic voltammetry (CV) results implied that the bioelectrochemical activity of exoelectrogens was promoted by nano-CeO₂. Electrochemical impedance spectroscopy (EIS) results revealed that the anodic charge transfer resistance of the MFC decreased with modified anode. This study demonstrates that the nano-CeO₂ can be an effective anodic catalyst for enhancing the power generation of MFC.     

Treatment of carbon fiber brush anodes for improving power generation in air-cathode microbial fuel cells

Carbon brush electrodes have been used to provide high surface areas for bacterial growth and high power densities in microbial fuel cells (MFCs). A high-temperature ammonia gas treatment has been used to enhance power generation, but less energy-intensive methods are needed for treating these electrodes in practice. Three different treatment methods are examined here for enhancing power generation of carbon fiber brushes: acid soaking (CF-A), heating (CF-H), and a combination of both processes (CF-AH). The combined heat and acid treatment improve power production to 1370 mW m⁻², which is 34% larger than the untreated control (CF-C, 1020 mW m⁻²). This power density is 25% higher than using only acid treatment (1100 mW m⁻²) and 7% higher than that using only heat treatment (1280 mW m⁻²). XPS analysis of the treated and untreated anode materials indicates that power increases are related to higher N1s/C1s ratios and a lower C-O composition. These findings demonstrate efficient and simple methods for improving power generation using graphite fiber brushes, and provide insight into reasons for improving performance that may help to further increase power through other graphite fiber modifications.     

Electricity generation from sediment microbial fuel cells with algae-assisted cathodes

One major limiting factor for sediment microbial fuel cells (SMFC) is the low oxygen reduction rate in the cathode. The use of the photosynthetic process of the algae is an effective strategy to increase the oxygen availability to the cathode. In this study, SMFCs were constructed by introducing the algae (Chlorella vulgaris) to the cathode, in order to generate oxygen in situ. Cyclic voltammetry and dissolved oxygen analysis confirmed that C. vulgaris in the cathode can increase the dissolved oxygen concentration and the oxygen reduction rate. We showed that power generation of SMFC with algae-assisted cathode was 21 mW m⁻² and was further increased to 38 mW m⁻² with additional carbon nanotube coating in the cathode, which was 2.4 fold higher than that of the SMFC with bare cathode. This relatively simple method increases the oxygen reduction rate at a low cost and can be applied to improve the performance of SMFCs.     

Macaroon-like FeCo2O4 modified activated carbon anode for enhancing power generation in direct glucose fuel cell

Macaroon-like FeCo₂O₄ nanomaterial was prepared and used as electrocatalyst in direct glucose alkaline fuel cell (DGAFC), which exhibited high catalytic activity towards glucose oxidation reaction. Maximum power density of 35.91 W m⁻² was achieved in the DGAFC equipped with a FeCo₂O₄ modified activated carbon (AC) anode, which was almost 151% higher than the control. Physical and electrochemical characterizations were performed to provide further understanding of the origin of its high activity. Our results show that the introduction of FeCo₂O₄ into the AC anode remarkably increase the exchange current density and reduce the charge transfer resistance. It is supposed that there is a synergistic effect between Fe (III) and Co (III), which accelerates electron transfer from glucose to external circuits. This study will promote the development of cost effective and environmentally benign catalysts for electrochemical energy applications.     

Analysis of chitin particle size on maximum power generation, power longevity, and Coulombic efficiency in solid-substrate microbial fuel cells

Microbial fuel cells (MFCs) produce bioelectricity from a wide variety of organic and inorganic substrates. Chitin can be used as a slowly degrading substrate in MFCs and thus as a long-term fuel to sustain power by these devices in remote locations. However, little is known about the effects of particle size on power density and length of the power cycle (longevity). We therefore examined power generation from chitin particles sieved to produce three average particle sizes (0.28, 0.46 and 0.78 mm). The longevity increased from 9 to 33 days with an increase in the particle diameter from 0.28 to 0.78 mm. Coulombic efficiency also increased with particle size from 18% to 56%. The maximum power density was lower for the largest (0.78 mm) particles (176 mW m⁻²), with higher power densities for the 0.28 mm (272 mW m⁻²) and 0.46 mm (252 mW m⁻²) particle sizes. The measured lifetimes of these particles scaled with particle diameter to the 1.3 power. Application of a fractal dissolution model indicates chitin particles had a three-dimensional fractal dimension between 2 and 2.3. These results demonstrate particles can be used as a sustainable fuel in MFCs, but that particle sizes will need to be controlled to achieve desired power levels.     

Power generation using carbon mesh cathodes with different diffusion layers in microbial fuel cells

An inexpensive carbon material, carbon mesh, was examined to replace the more expensive carbon cloth usually used to make cathodes in air-cathode microbial fuel cells (MFCs). Three different diffusion layers were tested using carbon mesh: poly(dimethylsiloxane) (PDMS), polytetrafluoroethylene (PTFE), and Goretex cloth. Carbon mesh with a mixture of PDMS and carbon black as a diffusion layer produced a maximum power density of 1355 ± 62 mW m⁻² (normalized to the projected cathode area), which was similar to that obtained with a carbon cloth cathode (1390 ± 72 mW m⁻²). Carbon mesh with a PTFE diffusion layer produced only a slightly lower (6.6%) maximum power density (1303 ± 48 mW m⁻²). The Coulombic efficiencies were a function of current density, with the highest value for the carbon mesh and PDMS (79%) larger than that for carbon cloth (63%). The cost of the carbon mesh cathode with PDMS/Carbon or PTFE (excluding catalyst and binder costs) is only 2.5% of the cost of the carbon cloth cathode. These results show that low cost carbon materials such as carbon mesh can be used as the cathode in an MFC without reducing the performance compared to more expensive carbon cloth.     

Analysis of microbial diversity of inocula used in a five-face parallelepiped and standard microbial fuel cells

This work had a double purpose: (i) to study the effect of sulphate-reducing (SR-In) and enriched (E-In) inocula on the characteristics of one-chamber standard microbial fuel cell (MFC-S) and parallelepiped cell and (ii) to analyze the bacterial communities in cells operated with either SR-In or E-In. The MFC-S of 150 mL consisted of one-chamber plexiglass cell with electrodes separated 7.8 cm. The MFC-P consisted of a parallelepiped built in plexiglass with a liquid volume of 270 mL. Five faces of this cell were fitted with ‘sandwich’ cathode–membrane–anode assemblages (CMA). The values of internal resistance (R_int) were 4602 and 687 Ω, for the MFC-S loaded with SR-In and E-In, respectively. The values of R_int were 400 and 84, and 292 and 80 Ω for the faces connected in series and parallel and the MFC-P loaded with SR-In and E-In, respectively. Parallel connection of cell faces also significantly improved the electrochemical characteristics of the P cell (higher powers). In general, use of E-In in both types of MFC lead to improved power densities compared to SR-In. Molecular biology analysis of microbial communities showed that the E-In was less diverse than SR-In (in terms of phyla). An electrochemically active bacterium Geovibrio ferrireducens belonging to phylum Deferribacteres was found in the E-In. Predominance of Deferribacteres was observed in the E-In. Members of this phylum were not found in the SR-In.     

Integration of direct carbon and hydrogen fuel cells for highly efficient power generation from hydrocarbon fuels

In view of impending depletion of hydrocarbon fuel resources and their negative environmental impact, it is imperative to significantly increase the energy conversion efficiency of hydrocarbon-based power generation systems. The combination of a hydrocarbon decomposition reactor with a direct carbon and hydrogen fuel cells (FC) as a means for a significant increase in chemical-to-electrical energy conversion efficiency is discussed in this paper. The data on development and operation of a thermocatalytic hydrocarbon decomposition reactor and its coupling with a proton exchange membrane FC are presented. The analysis of the integrated power generating system including a hydrocarbon decomposition reactor, direct carbon and hydrogen FC using natural gas and propane as fuels is conducted. It was estimated that overall chemical-to-electrical energy conversion efficiency of the integrated system varied in the range of 49.4–82.5%, depending on the type of fuel and FC used, and CO₂ emission per kW_elh produced is less than half of that from conventional power generation sources.     

微生物燃料电池产电性能试验研究

以双室微生物燃料电池为研究对象,考察了电极间距、电极面积比和阳极室填充活性炭颗粒,阳极室填充液浓度、pH值、流通速度对微生物燃料电池输出电压和功率密度的影响,通过分析建立最优双室微生物燃料电池模型。研究结果表明,微生物燃料电池的最大输出电压为544.3 mV,最大功率密度为341.38 mW/m2,在微生物燃料电池运行1 500 min后,利用极化曲线法测定电池的内阻为375Ω。     

Enhanced bioelectricity generation and cathodic oxygen reduction of air breathing microbial fuel cells based on MoS2 decorated carbon nanotube

Increasing efforts have been devoted to enhancing the cathode activity towards oxygen reduction and improve power generation of air breathing microbial fuel cells. Exploring non-precious metal and highly active cathodic catalyst plays a key role in improving cathode performance. Our work aims to investigate the electrocatalyst behavior and power output of the single-chamber MFC equipped with carbon nanotubes hybridized molybdenum disulfide nanocomposites (CNT/MoS₂) cathode. MoS₂ nanosheets embedded into the CNTs network structure is synthesized by a facile hydrothermal method. The CNT/MoS₂-MFC achieves a maximum power density of 53.0 mW m⁻², which is much higher than those MFCs with pure CNTs (21.4 mW m⁻²) or solely MoS₂ (14.4 mW m⁻²) cathode. The oxygen reduction reaction (ORR) test also demonstrates a promoted electrocatalytic activity of synthesized material, which may be attributed to the special interlaced structure and abundant oxygen chemisorption sites of CNT/MoS₂. Such CNTs-based noble-metal-free catalyst presents a new approach to the application of MFCs cathode materials.     

Insights into discrepancy in power generation among glucose and malate grown Rubrivivax benzoatilyticus JA2 microbial fuel cells

In this study, Rubrivivax benzoatilyticus JA2^T (=ATCC BAA-35^T = JCM 13220^T = MTCC 7087^T), an anoxygenic photosynthetic bacterium, was subjected to altered conditions and observed for changes in power outcome in the two chambered microbial fuel cells (MFCs), the basis of which was established using metabolomic studies. This is an extension to our previous studies, which showed that, under photo heterotrophic conditions, glucose in the form of a solitary carbon resource in minimal media, caused the strain JA2 to exhibit altered growth rates, progressive loss of pigmentation and reduced cell size (3–4 μm), compared to malate grown cells (6–7 μm). When R. benzoatilyticus JA2 cells were grown in malate bio-anodes, they presented higher potentials (289.22 ± 4.6 mV or 436.22 OCV per mg dry weight) compared to glucose bioanodes (163 ± 5.5 mv or 188.98 OCV per mg dry weight). Insights from the metabolomic footprints and fingerprints have revealed differential regulation of key components in the central metabolic pathway such as fumarate, citrate and succinate, which are significantly increased in malate grown bio anodes. Strain JA2 cells when grown with malate as substrate are densely grown on the electrodes and exhibited reduced size, when observed under SEM, which contrasts with control cells grown on malate broth. The artificial selection pressure of the MFC and the different metabolic pathways followed by these bacteria are the reasons for such discrepancy in the power production by the strain JA2. These adaptations may indicate survival advantage during the electron transfer and growth in bio anodes. The study throws light on what types of effluents would be more suitable as substrates for R. benzoatilyticus JA2 microbial fuel cells.     

Economic optimization of stacked microbial fuel cells to maximize power generation and treatment of wastewater with minimal operating costs

This study proposes an optimization-based strategy to select the best electrical stacking configuration of microbial fuel cells to achieve the highest power output and chemical oxygen demand removal under the lowest operating costs. Three similar wastewater-fed continuous flow microbial fuel cells are electrically connected in four different modes and concentrations of fuel substrate and buffer in anolyte, as main operating cost items, are optimized using two-level factorial design with the dual objective of maximizing power density and minimizing operating costs. In series connection the lowest ratio of operating costs to maximum power $0.048.mW⁻¹.d⁻¹ is achieved that is comparable to the ratio of $0.046.mW⁻¹.d⁻¹ for an individual unit as control. Optimization reduces operating costs 61% with only 37% reduction in maximum power compared to maximum attainable power. At the optimized concentrations, the lowest operating costs to chemical oxygen demand removal ratio $2.01.COD⁻¹ is observed in series connection. This suggests that the cheapest way to stack microbial fuel cells to gain the highest power output and chemical oxygen demand removal is serial electrical connection.     

Kinetics and performance evaluation of microbial fuel cell supplied with dairy wastewater with simultaneous power generation

Due to the growing demand for energy in the present-day world, it is obligatory to look for alternative sources of renewable energy. The derivation of power from microbial fuel cells (MFCs) has developed at the vanguard of the alternative source of renewable energy through the concomitant treatment of wastewater. Hence, the process development of MFC is obligatory for creating a sustainable source of renewable energy through the treatment of wastewater. To that end, an attempt was taken in the present study for sustainable power generation from single chamber microbial fuel cell (SCMFC) using Pseudomonas aeruginosa-MTCC-7814. The experiments were carried out in a batch process for 15 days with real dairy wastewater (RDW) having initial chemical oxygen demand (COD) of 8000 mg/L. The open-circuit voltage (OCV) found after 72 h of batch operation was 658 mV, which was maximum within the batch operation. The columbic efficiency (CE) of the batch process was found to be 46.59%. The maximum specific growth rate (μ_max) of Pseudomonas aeruginosa-MTCC-7814 was found to be 0.432 day^?1 during batch operation. However, saturation constant (Ks) and inhibition coefficient (K_i) were calculated as 608.74 mg/L, and 6582 mg/L, respectively. The maximum current density (I_max) and saturation constant (K_c) predicted from batch kinetics study were 132 mA/m² and 321 mg/L, respectively, which has resemblance with the data obtained from experiments. The maximum current density and power density from experiments were found to be 161 mA/m² and 34.82 mW/m², respectively. Results showed that a higher power density and current density values were obtained from the present study as compared to the earlier reports that utilized wastewater as the substrate for the MFC. Thus, the study suggests that Pseudomonas aeruginosa, (MTCC-7814) can be used as a promising biocatalyst in MFC for sustainable power generation through the utilization of wastewater treatment.     

Influence of biomass addition on electricity harvesting from solid phase microbial fuel cells

In this study, two types of biomass (Acorus calamus leaves and wheat straw) were added to a matrix of sediment and soil inside the anode of solid phase microbial fuel cells (SMFCs) in order to increase their output power. SMFC containing 3% leaves in their sediment had a maximum power density of 195 mW m⁻² in contrast to 4.6 mW m⁻² of that SMFC without leaves. Similarly, SMFC containing 1% wheat straw in their soil environment had a maximum power density of 167 mW m⁻². It suggests that the addition of biomass in appropriate proportions increases contact opportunities between the matrix, the anode and the added biomass, increases organic matter content, and enhances cellulase activity, thus serving as an important method for enhancing output power in SMFCs.     

Power generation and organics removal from wastewater using activated carbon nanofiber (ACNF) microbial fuel cells (MFCs)

Carbon-based materials are the most commonly used electrode material for anodes in microbial fuel cell (MFC), but are often limited by their surface areas available for biofilm growth and subsequent electron transfer process. This study investigated the use of activated carbon nanofibers (ACNF) as the anode material to enhance bacterial biofilm growth, and improve MFC performance. Qualitative and quantitative biofilm adhesion analysis indicated that ACNF exhibited better performance over the other commonly used carbon anodes (granular activated carbon (GAC), carbon cloth (CC)). Batch-scale MFC tests showed that MFCs with ACNF and GAC as anodes achieved power densities of 3.50 ± 0.46 W/m³ and 3.09 ± 0.33 W/m³ respectively, while MFCs with CC had a lower power density of 1.10 ± 0.21 W/m³ In addition, the MFCs with ACNF achieved higher contaminant removal efficiency (85 ± 4%) than those of GAC (75 ± 5%) and CC (70 ± 2%). This study demonstrated the distinct advantages of ACNF in terms of biofilm growth and electron transport. ACNF has a potential for higher power generation of MFCs to treat wastewaters.     

Integration of direct carbon fuel cells with concentrated solar power

In this paper, we will report on a study on the thermodynamic feasibility of a concept that realizes the cracking of methane with a concentrated solar power (CSP) reactor and electricity production with a direct carbon fuel cell (DCFC) and its possible contribution to a clean energy supply for Europe in the long-term future. The natural gas (methane) is decomposed in an endothermic reaction into hydrogen and carbon. The separated carbon is fed to a direct carbon fuel cell (DCFC) and converted with high efficiency to electric power. A model of the proposed concept is carried out in the flow sheet program Cycle-Tempo and the results of the simulations and the corresponding analysis are presented in this paper. Finally the location factors influencing the implementation of this concept in the north of Africa are evaluated.     

Performance of two different types of anodes in membrane electrode assembly microbial fuel cells for power generation from domestic wastewater

Graphite fiber brush electrodes provide high surface areas for exoelectrogenic bacteria in microbial fuel cells (MFCs), but the cylindrical brush format limits more compact reactor designs. To enable MFC designs with closer electrode spacing, brush anodes were pressed up against a separator (placed between the electrodes) to reduce the volume occupied by the brush. Higher maximum voltages were produced using domestic wastewater (COD = 390 ± 89 mg L⁻¹) with brush anodes (360 ± 63 mV, 1000 Ω) than woven carbon mesh anodes (200 ± 81 mV) with one or two separators. Maximum power densities were similar for brush anode reactors with one or two separators after 30 days (220 ± 1.2 and 240 ± 22 mW m⁻²), but with one separator the brush anode MFC power decreased to 130 ± 55 mW m⁻² after 114 days. Power densities in MFCs with mesh anodes were very low (<45 mW m⁻²). Brush anodes MFCs had higher COD removals (80 ± 3%) than carbon mesh MFCs (58 ± 7%), but similar Coulombic efficiencies (8.6 ± 2.9% brush; 7.8 ± 7.1% mesh). These results show that compact (hemispherical) brush anodes can produce higher power and more effective domestic wastewater treatment than flat mesh anodes in MFCs.     

Na_2SO_4·10H_2O复合相变储能体系的热力学测试

制备了一种Na2SO4.10H2O共晶相变蓄冷材料,其相变温度在8℃左右,可作为空调蓄冷材料。本文主要研究了复合相变体系的热化学性质和材料的相变特性。本研究测定出材料的相变潜热为114.37kJ/kg,固体平均比热容为4.68kJ/(kg.K),液体平均比热容为16.18kJ/(kg.K)。材料的主要成分为Na2SO4.10H2O,NaCl,NH4Cl,羧甲基纤维素(CMC)等,其主要特点是原料来源丰富,潜热和显热蓄冷量较大。     

Hybrid power generation system of solar energy and fuel cells

This paper introduces the methods of integration of solar energy and low‐temperature solid oxide fuel cells. On the one hand, we design the system that integrates the solar photovoltaic cells and fuel cells. On the other hand, solar energy is concentrated to heat up the fuel cell and supply the working temperature at hundreds Celsius degrees by Fresnel lens. Then the fuel conversion efficiency is increased because of gain from the solar energy. Moreover, integration of solar thermal energy power system with the fuel is a good method for resolving the instability of solar energy. CHP (combined heat and power) is another aspect to enhance the design hybrid system overall efficiency. Finally, we present a novel device but built on different scientific principle. It can convert solar energy and chemical energy of fuel to electric energy simultaneously within the same device to integrated solar cell and fuel cell from the device level. Copyright © 2016 John Wiley & Sons, Ltd.     

微生物燃料电池MnO_2及活性炭混合催化剂的制备及其性能研究

利用机械混合及化学复合两种混合方式制备出用于微生物燃料电池(MFC)阴极的Mn O_2与活性炭导电材料的混合催化剂,混合质量比分别为1∶3,1∶1和3∶1。将以各催化剂制作的碳布阴极置于空气阴极MFC中运行,利用线性扫描伏安法测试碳布阴极的性能。研究表明,两种混合催化剂均在混合质量比为1∶1时具有最佳性能;化学复合催化剂MFC的最大功率密度达到336 m W/m~2,是单纯使用Mn O_2粉末时的2.51倍,优于机械混合的催化剂。