石墨烯基杂化材料在微生物燃料电池电极中的应用

微生物燃料电池（MFC）是利用生物催化剂将污水有机物中的化学能直接转化为电能的技术,因其功率密度和能量转化效率低,电极制作成本高,限制了其大规模实际应用。因此如何提高电极的催化性能并降低电极制作成本成为MFC的研究重点方向。由于石墨烯基杂化材料具有良好的导电性和催化特性,因此石墨烯基杂化材料成为在MFC电极应用中的热点之一。本文综述了近年来MFC石墨烯基杂化电极材料的最新研究进展,重点讨论了改性石墨烯电极、金属及非金属/石墨烯杂化电极、金属氧化物/石墨烯杂化电极、聚合物/石墨烯杂化电极和石墨烯凝胶电极的设计思路和制备方法及其催化性能,着重分析了石墨烯基阳极和阴极杂化材料对MFC产电性能的影响。最后对石墨烯基杂化材料在MFC应用中存在的问题及研究前景进行了总结和展望。     

Microbial Fuel Cells: The Effects of Configurations,Electrolyte Solutions,and Electrode Materials on Power Generation

This objective of this study is to conduct a systematic investigation of the effects of configurations, electrolyte solutions, and electrode materials on the performance of microbial fuel cells (MFC). A comparison of voltage generation, power density, and acclimation period of electrogenic bacteria was performed for a variety of MFCs. In terms of MFC configuration, membrane-less two-chamber MFCs (ML-2CMFC) had lower internal resistance, shorter acclimation period, and higher voltage generation than the conventional two-chamber MFCs (2CMFC). In terms of anode solutions (as electron donors), the two-chamber MFCs fed with anaerobic treated wastewater (AF-2CMFCs) had the power density 19 times as the two-chamber MFCs fed with acetate (NO₃ ⁻2CMFCs). In terms of cathode solutions (as electron acceptors), AF-2CMFCs with ferricyanide had higher voltage generation than that of ML-2CMFCs with nitrate (NO₃ ⁻ML-2CMFCs). In terms of electrode materials, ML-2CMFCs with granular-activated carbon as the electrode (GAC-ML-2CMFCs) had a power density 2.5 times as ML-2CMFCs with carbon cloth as the electrode. GAC-ML-2CMFCs had the highest columbic efficiency and power output among all the MFCs tested, indicating that the high surface area of GAC facilitate the biofilm formation, accelerate the degradation of organic substrates, and improve power generation.     

Comparative Study of Electrochemical Performance and Microbial Flora in Microbial Fuel Cells by Using Three Kinds of Substrates

This work aimed to investigate the distinct electrochemical performance and microbial flora of microbial fuel cells(MFCs)in relation to different single hazardous fed fuels.Three replicate MFCs were inoculated with the same microbial consortium from a coking wastewater treatment plants wherein ammonium chloride(ammoniiim chlo-ride-fed MFC,N-MFC),phenol(phenol-fed MFC,P-MFC)and potassium sulphide(potassium sulphide-fed MFC,S-MFC)were the sole substrates and main components of real coking wastewater.With initial concentrations of am-monium chloride,phenol and potassium sulphide of 0.75,0.60 and 0.55 g/L,the removal efficiencies reached 95.6%,90.6%and 99.9%,respectively,whereas the peak output power densities totalled 697,324 and 1215 mW/m^2.Micro-bial community analysis showed that the respective addition of substrate substantially altered the microbial community structure of anode biofllm,resulting in changes in relative abundance and emergence of new strains and further affecting the electrochemical properties of MFCs.The chemical oxygen demand(COD)removal efficiency of real coking wastewater,in which,the inoculum was the combined biomass from the three MFCs,reached 82.3%.     

阳极电势对Geobacter sulfurreducens产电性能的影响

以产电模式菌Geobacter sulfurreducens为研究对象接种两瓶型微生物燃料电池(MFC)阳极室, 利用恒电位仪控制阳极电势, 考察了7种电势条件下MFC的启动期、最大功率密度和阳极生物量的变化情况. 研究结果表明, 当阳极电势为-250, -100和50 mV(vs. SCE)时, MFC启动较快, CV曲线和极化曲线表明, 在这3种电势条件下, MFC产电性能增强, 其中阳极电势为-100 mV时, MFC最大功率密度为1.67 W/m³, 比固定外阻条件下启动的MFC最大功率密度提高了5倍. 控制合适的阳极电势可以使阳极生物量提高2.5~3倍.     

Electricity production by a microbial fuel cell fueled by brewery wastewater and the factors in its membrane deterioration

Electricity production from brewery wastewater using dual-chamber microbial fuel cells (MFCs) with a tin-coated copper mesh in the anode was investigated by changing the hydraulic retention time (HRT). The MFCs were fed with wastewater samples from the inlet (inflow, MFC-1) and outlet (outflow, MFC-2) of an anaerobic digester of a brewery wastewater treatment plant. Both chemical oxygen demand removal and current density were improved by decreasing HRT. The best MFC performance was with an HRT of 0.5 d. The maximum power densities of 8.001 and 1.843 μW/cm2 were obtained from reactors MFC-1 and MFC-2, respectively. Microbial diversity at different condi-tions was studied using PCR-DGGE profiling of 16S rRNA fragments of the microorganisms from the biofilm on the anode electrode. The MFC reactor had mainlyGeobacter,Shewanella, andClostridium species, and some bacteria were easily washed out at lower HRTs. The fouling characteristics of the MFC Nafion membrane and the resulting degradation of MFC performance were examined. The ion exchange capacity, conductivity, and diffusivity of the membrane decreased significantly after foul-ing. The morphology of the Nafion membrane and MFC degradation were studied using scanning electron microscopy and attenuated total reflection-Fourier transform infrared spectroscopy.     

Impact of modified electrodes on boosting power density of microbial fuel cell for effective domestic wastewater treatment:A case study of Tehran

Utilizing microbial fuel cells (MFCs) is a promising technology for energy-efficient domestic wastewater treatment, but it still faces practical barriers such as low power generation. In this study, the LaMnO₃ perovskite-type oxide nanoparticles and nickel oxide/carbon nanotube/polyaniline (NCP) nanocomposite (the cathode and anode catalysts, respectively) have been prepared and used to enhance power density of MFC. The prepared La-based perovskite oxide catalysts were characterized by X-ray diffraction (XRD) and scanning electron microscopies (SEM). The electrocatalytic properties of the prepared catalysts were investigated through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) and Tafel plot at ambient temperature. Results show the exchange current densities of LaMnO₃/carbon cloth cathode and NCP nanocomposite/carbon cloth anode were 1.68 and 7 times more compared to carbon cloth cathode, respectively. In comparison to the bare carbon cloth anode, the MFC with the modified electrodes shows 11 times more enhancement in power density output which according to electrochemical results, it can be due to the enhancement of the electron transfer capability. These cathodic and anodic catalysts were examined in batch and semi-continuous modes to provide conditions close to industrial conditions. This study suggests that utilizing these low cost catalysts has promising potential for wastewater treatment in MFC with high power generation and good COD removal efficiency.     

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.     

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.     

A microfluidic microbial fuel cell array that supports long-term multiplexed analyses of electricigens

Microbial fuel cells (MFCs) are green energy technologies that exploit microbial metabolism to generate electricity. The widespread implementation of MFC technologies has been stymied by their high cost and limited power. MFC arrays in which device configurations or microbial consortia can be screened have generated significant interest because of their potential for defining aspects that will improve performance featuring high throughput characteristics. However, current miniature MFCs and MFC array systems do not support long-term studies that mimic field conditions, and hence, have limitations in fully characterizing and understanding MFC performances in varieties of conditions. Here, we describe an MFC array device that incorporates microfluidic technology to enable continuous long-term analysis of MFC performance at high throughput utilizing periodic anolyte/catholyte replenishment. The system showed 360% higher power output and 700% longer operating time when compared to MFC arrays without catholyte replenishment. We further demonstrate the utility of the system by reporting its successful use in screening microbial consortia collected from geographically diverse environments for communities that support enhanced MFC performance. Taken together, this work demonstrates that anolyte/catholyte replenishment can significantly improve the long-term performance of microfabricated MFC arrays, and support the characterization of diverse microbial consortia.     

Nanoporous gold electrode prepared from gold compact disk as the anode for the microbial fuel cell

The electrodes (anode and cathode) have an important role in the efficiency of a microbial fuel cell (MFC), as they can determine the rate of charge transfer in an electrochemical process. In this study, nanoporous gold electrode, prepared from commercially available gold-made compact disk, is utilized as the anode in a two-chamber MFC. The performance of nanoporous gold electrode in the MFC is compared with that of gold film, carbon felt and acid-heat-treated carbon felt electrodes which are usually employed as the anode in the MFCs. Electrochemical surface area of nanoporous gold electrode exhibits a 7.96-fold increase rather than gold film electrode. Scanning electron microscopy analysis also indicates the homogeneous biofilm is formed on the surface of nanoporous gold electrode, while the biofilm formed at the surface of acid-heat-treated carbon felt electrode shows rough structure. Electrochemical studies show although modifications applied on carbon felt electrodes improve its performance, nanoporous gold electrode, due to its structure and better electrochemical properties, acts more efficiently as the MFC’s anode. The maximum power density produced by nanoporous gold anode is 4.71 mW m^?2 at current density of 16.00 mA m^?2, while this value for acid-heat-treated carbon felt anode is 3.551 mW m^?2 at current density of 9.58 mA m^?2.     

Electrochemical treatment of slaughterhouse and dairy wastewater: Toward making a sustainable process

The industrial processing of meat and dairy production uses large amounts of fresh water, therefore, generates a significant volume of wastewaters. The treatment of these effluents has been performed using different technologies from biological to electrochemical advanced oxidation processes. Under the circular economy concept, the lack of available freshwater resources has increased the interest in reusing wastewater from slaughterhouses, and even in the recovering of by-products.This article reviews the application of electrochemical treatments to slaughterhouse and dairy wastewaters. In addition, an overview of added-value products and energy recovery from these industrial wastewaters is also presented with future perspectives.     

Microfuel cells: Modern state and future development (Review)

Literature sources of the last 15 years were analyzed and the results were considered for the studies carried out in one of the directions of hydrogen power engineering of the most current interest: development of portable low-power fuel cells (microfuel cells, MFCs). MFCs with high power density and high efficiency are used as a basis for a new generation of power sources for various stand-alone electronic devices. The latest silicon micro- and nanotechnologies are considered, same as the technologies for obtaining nanostructured catalysts and problems regarding development of MFCs with the power of 0.5–20 W, methods of catalytic layers application in MFCs, choice of fuel, and methods of supplying it into MFCs, and MFC water managemen and temperature control. Special attention was paid to borohydride MFCs, combined (hybrid) systems, and MFCs with a mixed reagent. The results of electrochemical tests of MFC layouts are presented.     

Functional Nanomaterial-Modified Anodes in Microbial Fuel Cells: Advances and Perspectives

Microbial fuel cell (MFC) is a promising approach that could utilize microorganisms to oxidize biodegradable pollutants in wastewater and generate electrical power simultaneously. Introducing advanced anode nanomaterials is generally considered as an effective way to enhance MFC performance by increasing bacterial adhesion and facilitating extracellular electron transfer (EET). This review focuses on the key advances of recent anode modification materials, as well as the current understanding of the microbial EET process occurring at the bacteria-electrode interface. Based on the difference in combination mode of the exoelectrogens and nanomaterials, anode surface modification, hybrid biofilm construction and single-bacterial surface modification strategies are elucidated exhaustively. The inherent mechanisms may help to break through the performance output bottleneck of MFCs by rational design of EET-related nanomaterials, and lead to the widespread application of microbial electrochemical systems.     

Microbial fuel cells using natural pyrrhotite as the cathodic heterogeneous Fenton catalyst towards the degradation of biorefractory organics in landfill leachate

An investigation aimed at checking the integration of cathodic pyrrhotite Fenton's reaction with anodic microbial respiration for the enhancement of MFC performance and treatment of a real landfill leachate was carried out. The MFC equipped with a pyrrhotite-coated graphite-cathode generated the maximum power density of 4.2 W/m³ that was 133% higher than graphite-cathode. Concomitantly, electrochemical impedance spectroscopy (EIS) showed that the polarization resistance of pyrrhotite-cathode (92 Ω) was much lower than the graphite-cathode (1057 Ω), indicating that the cathodic overpotential was significantly lowered, probably due to the occurrence of pyrrhotite Fenton's reaction. The in situ generation of Fenton's reagents (Fe²⁺ and H₂O₂) at the pyrrhotite-cathode was demonstrated by the cyclic voltammetry measurement. Besides, reactive oxygen species produced from the pyrrhotite Fenton's reaction were detected and demonstrated to be vital to the enhancement of MFC power output. Further, the effectiveness of this system was examined by treating an old-aged landfill leachate. 77% of color and 78% of COD were removed from the original leachate, indicating that the pyrrhotite not only acted as a cost-effective cathodic catalyst for MFCs in power generation, but also extended the practical merits of traditional MFCs towards advanced oxidation of biorefractory pollutants.     

微生物燃料电池生物阴极

微生物燃料电池(microbial fuel cells, MFCs)利用微生物处理废水的同时产电,是一种清洁可再生能源技术。近年来新兴起的生物阴极是指阴极室中的功能微生物附着在电极表面形成生物膜,电子由电极传递给微生物并发生相应的生物电化学反应;是微生物燃料电池研究的一个重要方向。本文根据厌氧、好氧操作体系的不同将生物阴极进行分类;归纳总结了微生物组成、电极和分隔材料的研究进展,探讨了生物阴极在去除污染物和生成高附加值产品中的实际应用,并提出了其将来发展的可能方向。     

Design of Clayware Separator-Electrode Assembly for Treatment of Wastewater in Microbial Fuel Cells

Performance of six different microbial fuel cells (MFCs) made from baked clayware, having 450 ml effective anodic chamber volume, was evaluated, with different configurations of separator electrode assemblies, to study the feasibility of bioelectricity generation and high-strength wastewater treatment in a single-chambered mediator-less air-cathode MFC. Superior performance of an air-cathode MFC (ACMFC) with carbon coating on both sides of the separator was observed over an aqueous cathode MFC, resulting in a maximum volumetric power of 4.38 W m^?3 and chemical oxygen demand (COD) removal efficiency of more than 90 % in a batch cycle of 4 days. Hydrophilic polymer polyvinyl alcohol (PVA) was successfully used as a binder. The problem of salt deposition and fouling of cathode could be minimized by using a sock net current collector, replacing the usual stainless steel wire. However, electrolyte loss due to evaporation is a problem that needs to be resolved for better performance of an ACMFC.     

用于生物电化学系统的石墨烯电极新进展

可持续社会的发展需要成本低, 并从废物或废水中提取能源或将能源转化为产品的环境友好技术. 近年兴起的生物电化学系统(BESs)利用微生物催化不同电化学反应, 是将废物或废水中能量转化为电能等多种产品的发展前景广阔的新技术. 当有关反应的吉布斯自由能小于零, 系统输出电能, 此时的BESs即为微生物燃料电池(MFCs); 相反, 若反应的吉布斯自由能为正值, 此时的BESs被称为微生物电解电池(MECs). 随着研究工作的不断深入和拓展, BESs的电极性能已成为制约其应用的瓶颈. 石墨烯以其独特的结构和优异的材料性能在BESs领域, 特别是MFCs中得以应用. 本文参考了最新的文献资料, 综述了石墨烯应用于BESs的发展现状, 包括应用于MFCs的石墨烯电极、掺杂石墨烯电极、担载石墨烯电极, 对其在MECs中可能的应用, 以及未来发展趋势予以展望.     

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.     

Power Generation Capabilities of Microbial Fuel Cells with Different Oxygen Supplies in the Cathodic Chamber

Two microbial fuel cells (MFCs) inoculated with activated sludge of a wastewater treatment plant were constructed. Oxygen was provided by mechanical aeration in the cathodic chamber of one MFC, whereas it was obtained by the photosynthesis of algae in the other. Electrogenic capabilities of both MFCs were compared under the same operational conditions. Results showed that the MFC with mechanical aeration in the cathodic chamber displayed higher power output than the one with photosynthesis of algae. Good linear relationship between power density and chemical oxygen demand (COD) loading rate was obtained only on the MFC with mechanical aeration. Furthermore, the relationships between power density and effluent COD and between Coulombic efficiency and COD loading rate can only be expressed as binary quadratic equations for the MFC with mechanical aeration and not for the one with photosynthesis of algae.     

Effect of Inoculum Types on Bacterial Adhesion and Power Production in Microbial Fuel Cells

Microbial fuel cell (MFC) is an emerging biotechnology to convert the organic substrates in wastewater to electricity by anaerobic electrogenic bacteria. The main challenge for MFC research is to elucidate the fundamental mechanisms of electron generation and transfer and to apply these mechanisms to improve the power production in the engineering operation. This study extensively investigated the effects of three inocula (Geobacter sulfurreducens, soil, and wastewater) on the power production and electrochemical characteristics (i.e., internal resistances, Coulombic Efficiency) of MFCs. The results showed that the extents of bacterial adhesion varied between mixed cultures (soil) and pure cultures (G. sulfurreducens). The voltage output increased 30% when bacterial adhesion was well-developed in the soil inocula. Meanwhile, the inoculum types clearly affected the internal resistance (R _in) and power production of MFCs. Pure culture inoculum (G. sulfurreducens) had the lowest R _in (165 Ω) and the highest Coulombic Efficiency (CE, 25.8%) and Energy Conversion Efficiency (ECE, 7.2%), while the mixed culture inocula (soil) with the high concentration of nonelectrogenic bacteria, exhibited the highest R _in (620 Ω), lowest CE (9.2%) and lowest ECE (2.4%). Additionally, a second-order correlation was established between the anode potential (P _A) and power output while an exponential correlation was established between the difference between anode and cathode potentials (ΔP _C−A) and power output.