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.     

Nanomaterials Facilitating Conversion Efficiency Strategies for Microbial CO2 Reduction

Microbial electro- and photoelectrochemical CO₂ reduction represents an opportunity to tackle the environmental demand for sustainable fuel production. Nanomaterials critically impact the electricity- and solar-driven microbial CO₂ reduction processes. This minireview comprehensively summarizes the recent developments in the configuration and design of nanomaterials for enhancement of the bacterial adhesion and extracellular electron transfer (EET) processes, based on the modification technologies of improving chemical stability, electrochemical conductivity, biocompatibility, and surface area. Furthermore, the investigation of incorporating non-photosynthetic microorganisms using advanced light-harvesting nanostructured photoelectrodes for solar-to-chemical conversion, as well as the current understanding of EET mechanisms occurring at photosynthetic semiconductor nanomaterials-bacteria biohybrid interface is detailed. The crucial factors influencing the performance of microbial CO₂ reduction systems and future perspectives are discussed to provide guidance for the realization of their large-scale application.     

阳极改性对微生物燃料电池处理秸秆水解物性能影响

以玉米秸秆稀酸水解液为阳极底物,用污水处理厂活性污泥为产电微生物菌源构建双室微生物燃料电池(MFC),采用三种不同方法改性阳极碳毡,并对其MFC产电性能进行研究。结果表明,以未改性碳毡(CC)、HNO_3酸解CC(HNO_3/CC)、壳聚糖改性CC(chitosan/CC)、PDADMAC/α-Fe_2O_3层层自组装改性碳毡(PDADMAC/α-Fe_2O_3/CC)的MFC的最大产电量分别为248、315、452和522 mV,最大功率密度分别为54.6、92.7、203.8和248.1 mW/m~2,COD的去除率分别为82.21%、81.46%、82.53%和86.44%。循环伏安曲线显示,PDADMAC/α-Fe_2O_3层层自组装改性的阳极碳毡具有较高的氧化还原电位。电化学阻抗谱图表明,PDADMAC/α-Fe_2O_3层层自组装改性碳毡的极化内阻最小,为7Ω。几种改性材料为阳极的MFC性能依次为PDADMAC/α-Fe_2O_3/CC壳聚糖/CCHNO_3/CC空白CC。     

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.     

氧化还原导电水凝胶制备及其在微生物燃料电池的应用

微生物细胞与微生物燃料电池阳极之间的电子传递效率是影响产电性能的关键因素.借助阳极修饰可以促进电子转移速率,提高电池的性能.本文合成了一种以聚4-乙烯基吡啶为骨架,中性红单体为氧化还原活性中心、具有良好导电性和生物兼容性的氧化还原水凝胶材料.其中通过共价键合固定氧化还原中介体,避免了对外界环境的二次污染.以该材料修饰碳纸作为阳极组装电池,实验表明经过修饰的生物阳极驯化周期缩短,阳极电势更接近NADH/NAD的平衡电位.该电池的功率密度较未修饰的电极的电池有明显的提高.     

Bioenergetics and extracellular electron transfer in microbial fuel cells and microbial corrosion

Bioenergetics can be used to analyze the theoretical voltage output of a microbial fuel cell (MFC) and the thermodynamic driving force in microbiologically influenced corrosion (MIC). MFCs involve both inward and outward extracellular electron transfer (EET), whereas only inward EET is behind EET–MIC caused by an electroactive biofilm's harvest of energy from a metal. EET is often rate-limiting, and it is an important process in microbial energy metabolism. EET is critical to the understanding of MFCs and EET–MIC bioelectrochemical processes. Many advances have been made in the past decade on EET by MFC and MIC researchers. Gene manipulations have been used to improve EET in MFCs, leading to enhanced energy output. They have also been used to elucidate the EET processes for better understanding of EET–MIC, which aids in MIC analysis and decision-making of biocide treatment and its efficacy assessment. Researchers are starting to integrate EET knowledge from both fields.     

Applicability of Alginate Film Entrapped Yeast for Microbial Fuel Cell

New strategies are proposed for modification of the anode of a Microbial Fuel Cell (MFC). Immobilization of yeast cells as electrogenic microorganism in MFC was reported using alginate. Yeast cells entrapment within alginate matrices was done through films deposited at the surface of a carbon felt electrode and the resulting anodes were characterized by chronoamperometry. Yeast entrapped within alginate films on carbon felt oxidized glucose and generates a current by direct and mediated electrons transfer from yeast cells to the carbon electrode. The result substantiated that immobilization of yeast for MFC could be a promising method to product green electricity.

     

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.     

化学修饰炭黑在微生物燃料电池中的生物产电行为

研究发现微生物燃料电池从启动到稳定运行的过程中往往存在一种现象,就是在高电流密度下,微生物燃料电池的输出电压会出现逆转,从而限制了微生物燃料电池的规模化应用,以及它在污废水处理、脱盐等方面的功能.
　　前期研究发现,微生物燃料电池的性能逆转现象与阳极材料的电容性能有关.电极材料的电容越大,越有利于微生物燃料电池的产电性能稳定,换言之,阳极材料电容不足导致产电性能逆转.但是超级电容活性炭的制作工艺繁琐,成本高,且导电性弱,不能满足微生物燃料电池的应用需求.炭黑的导电能力强、化学稳定性高、成本低,但作为微生物燃料电池的阳极则产生产电性能逆转现象.
　　化学修饰(如酸、碱活化或者添加具有赝电容性质的金属氧化物等)可以提高材料的电容性能.低温条件(80 oC)下,对低电容材料—炭黑进行HNO3和KOH的化学活化处理,并在此基础上,进一步用5%Fe3O4修饰,采用辊压工艺,以质量分数为60%的聚四氟乙烯乳液为粘结剂,制作微生物燃料电池的阳极,与空气阴极构建单室微生物燃料电池系统.采用傅里叶变换红外光谱(FTIR)、比表面积测试、材料表面pH和X射线能量分析光谱(EDX)等手段表征炭黑活化前后的物理、化学性质;接触角润湿性测试表征活化前后电极表面的亲疏水性.电化学循环伏安法测试活化前后,电极的电子存储能力.
　　与蒸馏水的pH相比较,材料表面pH分析表明炭黑材料经化学活化处理后,其表面pH无明显变化; FTIR和EDX测试表明化学活化处理使得炭黑表面引入含O(N)官能团;吸附-脱附曲线分析表明化学活化后,炭黑的比表面积减小,微孔与介孔的体积比增加;接触角测试表明炭黑阳极活化处理后,电极表面亲水性增加;循环伏安测试证实,化学活化后的炭黑阳极电容得到0.1–0.8 F/cm2的增长.结合燃料电池的产电性能测试,发现只有当炭黑阳极电容不小于1.1 F/cm2时,微生物燃料电池的产电逆转现象才会消失.炭黑阳极的化学活化方法为微生物燃料电池的性能稳定提供了一种简便、低成本的方法.     

Facile Fabrication of Graphene‐Containing Foam as a High‐Performance Anode for Microbial Fuel Cells

Facile fabrication of novel three‐dimensional anode materials to increase the bacterial loading capacity and improve substrate transport in microbial fuel cells (MFCs) is of great interest and importance. Herein, a novel graphene‐containing foam (GCF) was fabricated easily by freeze‐drying and pyrolysis of a graphene oxide–agarose gel. Owing to the involvement of graphene and stainless‐steel mesh in the GCF, the GCF shows high electrical conductivity, enabling the GCF to be a conductive electrode for MFC applications. With the aid of agarose, the GCF electrode possesses a supermacroporous structure with pore sizes ranging from 100–200 μm and a high surface area, which greatly increase the bacterial loading capacity. Cell viability measurements indicate that the GCF possesses excellent biocompatibility. The MFC, equipped with a 0.4 mm‐thick GCF anode, shows a maximum area power density of 786 mW m^?2, which is 4.1 times that of a MFC equipped with a commercial carbon cloth anode. The simple fabrication route in combination with the outstanding electrochemical performance of the GCF indicates a promising anode for MFC applications.     

High‐efficiency Nitric Acid‐PPy/AQDS Coupling Treated Bioanodes Based Microbial Fuel Cell

The properties of anode material are crucial for high performances in microbial fuel cells (MFCs). Herein, we report a biocompatible, conductive, and electron transfer efficient cooperative processing anode, which is fabricated by electrodepositing polypyrrole/anthraquinone‐2, 6‐disulphonic disodium salt (PPy/AQDS) onto nitric acid‐soaked carbon felt. Results showed that the cooperative processing anode outperformed the pristine one in biomass, electrical conductivity, and exchange current density with better performance between 2.4 and 3.3 times. The maximum power density (1060.3 mW m⁻²) of the MFC equipped with the properties hybridized anode delivered a 2.2‐fold increase over that of the control and thus has great potential to be used as an anode for high‐power MFC. Further investigation revealed that the contributions of biocompatibility (BCB), electrical conductivity (EC), and electron transfer efficiency (ETE) to the performance of carbon felt anodes appeared as cumulative effect rather than summing effect. We propose combined treatment of BCB with EC and ETE to form a properties‐hybridized anode based on thoroughly analyzing the feasibility and effectiveness, and discussed future efforts to be made for realizing more extraordinary high‐performance cooperative processing anodes. This work may also provide a novel approach for the development of other types of anode for high‐performance MFC through combined treating the BCB with EC and ETE simultaneously.     

A μL-scale micromachined microbial fuel cell having high power density

We report a MEMS (Micro-Electro-Mechanical Systems)-based microbial fuel cell (MFC) that produces a high power density. The MFC features 4.5-μL anode/cathode chambers defined by 20-μm-thick photo-definable polydimethylsiloxane (PDMS) films. The MFC uses a Geobacter-enriched mixed bacterial culture, anode-respiring bacteria (ARB) that produces a conductive biofilm matrix. The MEMS MFC generated a maximum current density of 16,000 μA cm(-3) (33 μA cm(-2)) and power density of 2300 μW cm(-3) (4.7 μW cm(-2)), both of which are substantially greater than achieved by previous MEMS MFCs. The coulombic efficiency of the MEMS MFC was at least 31%, by far the highest value among reported MEMS MFCs. The performance improvements came from using highly efficient ARB, minimizing the impact of oxygen intrusion to the anode chamber, having a large specific surface area that led to low internal resistance.     

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.     

Graphene Oxide/Carbon Nanotube Composite Hydrogels—Versatile Materials for Microbial Fuel Cell Applications

Carbonaceous nanocomposite hydrogels are prepared with an aid of a suspension polymerization method and are used as anodes in microbial fuel cells (MFCs). (Poly N‐Isopropylacrylamide) (PNIPAM) hydrogels filled with electrically conductive carbonaceous nanomaterials exhibit significantly higher MFC efficiencies than the unfilled hydrogel. The observed morphological images clearly show the homogeneous dispersion of carbon nanotubes (CNTs) and graphene oxide (GO) in the PNIPAM matrix. The complex formation of CNTs and GO with NIPAM is evidenced from the structural characterizations. The effectual MFC performances are influenced by combining the materials of interest (GO and CNTs) and are attributed to the high surface area, number of active sites, and improved electron‐transfer processes. The obtained higher MFC efficiencies associated with an excellent durability of the prepared hydrogels open up new possibilities for MFC anode applications.

     

生物电化学系统降解多环芳烃萘及微生物群落研究

采用单室空气阴极微生物燃料电池(MFC)反应器构型, 以不同浓度萘为基底物质, 考察MFC的产电性能、 萘降解率、 化学需氧量(COD)和总有机碳含量(TOC)降解率及MFC阴阳极微生物活性和多样性. 结果表明, 循环伏安曲线受不同浓度萘的影响变化较为明显, 随着萘浓度的增大, 最大功率密度呈下降趋势, 且萘对MFC的阴极电极电势影响较大; 当萘的浓度为15 mg/L时, MFC最大功率密度可达(645.841±28.08) mW/m ²; 对萘的降解率高达100%, 且MFC对COD和TOC的降解率随着萘浓度的提高而增大, 但是增大的速率逐渐减小. 对MFC阳极微生物膜进行高通量测序发现, Geobacter是优势菌属, 相对丰度达81%, 阴极主要以Aquamicrobium为主.     

Amide-Functionalized Porous Carbonaceous Anode Materials for Lithium-Ion Batteries

Porous carbonaceous anode materials have received considerable attention as an alternative anode material, however, there is a critical bottleneck as it suffers from a large irreversible specific capacity loss over several initial cycles owing to undesired surface reactions. In order to suppress undesired surface reactions of porous carbonaceous anode material, here, we suggest a simple and convenient two-step surface modification approach that allows the embedding of an amide functional group on the surface of a porous carbonaceous anode, which effectively improves the surface stability. In this approach, the porous carbonaceous anode material is firstly activated by means of strong acid treatment comprising a combination of H₂SO₄ and HNO₃, and it is subjected to further modification by means of an amide coupling reaction. Our additional systematic analyses confirm that the acid functional group effectively transforms into the amide functional group. The resulting amide-functionalized porous carbon exhibits an improved electrochemical performance: the initial discharge specific capacity is greatly reduced to less than 2,620 mA h g⁻¹ and charge specific capacity is well still remained, indicating stabling cycling performance of the cell.     

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.     

高锰酸钾作阴极的微生物燃料电池

构建了一个以醋酸钠水溶液为阳极原料、高锰酸钾为阴极氧化剂的双室微生物燃料电池, 考察了阴极溶液浓度、阴极流动状态、外电阻和pH值等因素对电池性能的影响, 监测了电池外电压和两极电极电势的变化过程, 并分析了阴极极化的原因和限制微生物燃料电池(MFC)的关键因素. 研究结果显示: (1) MnO2在碳纸表面的沉积是阴极极化的主要原因, 而溶液流动可以明显降低极化程度; 将高锰酸钾溶解在缓冲溶液中可以进一步降低阴极H+浓差极化; (2) 根据极化曲线可以推断, 影响电池输出功率的决定性因素应是微生物代谢反应速度和微生物与电极之间的电子传递速率; (3) 随外电阻的变化, 电池输出功率出现极大值824 mW/m2, 相应外电阻为300 Ω左右, 这与通过I-V关系曲线推导得到的电池内阻(284±18) Ω相吻合; (4) pH值和高锰酸钾浓度对电池阴极电极电势的影响符合Nernst方程.     

微生物燃料电池中生物膜成长对电池电化学性能的影响

以大肠杆菌为接种体,葡萄糖为基质,在1 000 Ω恒外阻下生成电活性生物膜,研究了生物膜的形成对电池电化学行为的影响。应用循环伏安、阻抗测试、极化分析、输出功率和阳极电势来考察其电化学表现。研究结果表明,随着生物膜完全成熟,阳极极化电阻减小66.5%,阳极电势逐渐降低,最大输出功率密度增加260%。     

影响MFC产电能力及污水净化的非生物因素研究

以厌氧污泥接种模拟生活污水, 构建双室无介体型微生物燃料电池(MFC). 以输出功率密度、库仑效率和COD_Cr(化学需氧量)去除率为评价指标, 采用正交设计考察4种非生物因素(即阴、阳极材料、底物和电子受体)对MFC产电及污水净化的影响. 在此基础上进一步探讨阴极离子浓度对电能输出的影响. 结果表明: 对MFC产能及污水净化的影响因素顺序为: 电子受体＞阳极＞阴极＞底物, 最优组合为碳毡-乳酸钠-不锈钢板-铁氰化钾＋溶解氧|向阴极液中投加NaCl可使产电能力显著增强, 最佳投加量为150 mmol•L^－1. 同时, 阴极室定期添加铁氰化钾可维持电流稳定. 试验中, 葡萄糖型、乳酸钠型以及混合型底物模拟污水的COD_Cr均得到有效去除, 平均去除率达85.2%, 显示了研究的MFC具有很强的产电和污水净化能力.