Decorating anode with bamboo-like nitrogen-doped carbon nanotubes for microbial fuel cells

Anode electrodes play a key role in generating electricity from microbial fuel cells (MFCs) because they directly affect microbial activities. This communication reports the preparation of nitrogen-doped carbon nanotubes with a bamboo-like nanostructure (Bamboo-NCNTs) by catalytic pyrolysis of ethylene diamine and application of the Bamboo-NCNTs as anode-modifying materials in MFCs. The Bamboo-NCNTs significantly improved performance of an MFC in current production and power output, and reduced internal resistance of the anode compared with conventional CNTs-modified and unmodified anodes. The improved performance could be attributed to the increased active sites induced by multiple joint structures and enhanced biocompatibility originated from nitrogen dopant.     

Enhanced power production of microbial fuel cells by reducing the oxygen and nitrogen functional groups of carbon cloth anode

The physicochemical properties of anode material are important for the electron transfer of anode bacteria and electricity generation of microbial fuel cells (MFCs). In this work, carbon cloth anode was pretreated with isopropanol, hydrogen peroxide (H₂O₂) and sodium hypochlorite (NaOCl) in order to reduce the anode functional groups. The influence of functional groups on the electrochemical properties of carbon cloth anode and power generation of MFCs was investigated. The anode pretreatments removed the surface sizing layer of carbon cloth and substantially reduced the contents of C‐O and pyridinic/pyrrolic N groups on the anode. Electrochemical impedance spectroscopy and cyclic voltammetry analyses of the biofilm‐matured anodes revealed an enhanced electrochemical electron transfer property because of the anode pretreatments. As compared with the untreated control (612 ± 6 mW m^?2), the maximum power density of an acetate‐fed single‐chamber MFC was increased by 26% (773 ± 5 mW m^?2) with the isopropanol treated anode. Additional treatment with H₂O₂ and NaOCl further increased the maximum power output to 844 ± 5 mW m^?2 and 831 ± 4 mWm^?2. A nearly inverse liner relationship was observed between the contents of C‐O and pyridinic/pyrrolic N groups on anodes and the anodic exchange current density and the power output of MFCs, indicating an adverse effect of these functional groups on the electricity production of anodes. Results from this study will further our understanding on the microbial interaction with carbon‐based electrodes and provide an important guidance for the modification of anode materials for MFCs in future studies. Copyright © 2016 John Wiley & Sons, Ltd.     

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.     

Melamine modified carbon felts anode with enhanced electrogenesis capacity toward microbial fuel cells

Surface electropositivity and low internal resistance are important factors to improve the anode performance in microbial fuel cells(MFCs). Nitrogen doping is an effective way for the modification of traditional carbon materials. In this work, heat treatment and melamine were used to modify carbon felts to enhance electrogenesis capacity of MFCs. The modified carbon felts were characterized using X-ray photoelectron spectroscopy(XPS), scanning electron microscope(SEM), atomic force microscopy(AFM)and malvern zeta potentiometer. Results show that the maximum power densities under heat treatment increase from 276.1 to 423.4 m W/m~2(700 °C) and 461.5 m W/m~2(1200 °C) and further increase to472.5 m W/m~2(700 °C) and 515.4 m W/m~2(1200 °C) with the co-carbonization modification of melamine.The heat treatment reduces the material resistivity, improves the zeta potential which is beneficial to microbial adsorption and electron transfer. The addition of melamine leads to the higher content of surface pyridinic and quaternary nitrogen and higher zeta potential. It is related to higher MFCs performance. Generally, the melamine modification at high temperature increases the feasibility of carbon felt as MFCs' s anode materials.     

Facile Synthesis of Hierarchical Hollow CoP@C Composites with Superior Performance for Sodium and Potassium Storage

Hierarchical hollow CoP and carbon composites were obtained through a facile synthetic method, where carbonization and phosphorization of the precursor were completed within one single step. The composites are composed of hollow CoP@C spheres, which are further made up of CoP nanoparticles with a thin outer carbon layer. Electrochemical performances of the prepared CoP@C composites as anodes for sodium and potassium storage were evaluated and compared. In situ TEM, in situ synchrotron XRD, and DFT calculations were conducted to study the structural evolution and the interaction between Na/K and CoP during cycling processes. Benefiting from the synergistic effect of conductive carbon layer and hierarchical hollow structure, the as‐prepared CoP@C composites demonstrate superior sodium and potassium storage capability as anode materials for rechargeable batteries.     

微生物阳极燃料电池极性反转现象研究

本文在构建出微生物阳极燃料电池系统的基础上,研究了微生物燃料电池极性反转现象. 实验表明,由活性污泥混合菌源接种的微生物阳极在电极表面形成电化学生物膜,但平行构建的微生物阳极燃料电池系统在内阻、输出电压和放电时长等方面存在着不同程度差异. 在串联微生物燃料电池组中,放电操作会导致性能较差的微生物单电池首先出现极性反转. 电极电势测量表明,较高的放电电流使微生物阳极电势迅速正移,导致电池系统出现极性反转. 在室温范围内,温度升高可使MFC承受较高的放电电流,不易发生极化. 燃料物质缺乏时,MFC易发生极性反转,但过高的电流仍能使燃料物质充分的MFC出现极性反转. MFC极性反转会对微生物阳极性能造成影响. 极性反转时间较短(<5 min),对微生物阳极影响不大,但延长极性反转时间,会导致微生物阳极性能下降.     

碳电极上电沉积的Ni-MgO纳米复合物催化甲醇和乙醇电氧化反应

在细小MgO增强颗粒的存在下,采用电沉积法在碳阳极上经瓦特镍制得Ni–MgO纳米复合物,考察了它在碱性介质中电催化氧化甲醇和乙醇反应性能,并与碳涂覆的纯Ni催化剂(Ni/C)性能进行了比较。运用能量散射谱、X射线衍射和扫描电镜分别表征了沉积的纳米复合物的化学组成、相结构和表面形貌,并采用循环伏安法(CV)、计时电流法和电化学阻抗谱(EIS)等电化学技术考察了所制电催化剂阳极的催化活性。结果表明, Ni/C催化剂在电氧化反应中表现出很低的催化活性和稳定性,而MgO的引入显著增加了Ni催化剂在醇氧化反应中的催化活性和抗中毒性能。 EIS和CV结果证实Ni–MgO/C纳米复合物电极具有比Ni/C更低的电荷转移阻力和更高的抗中毒性能。     

Drop impact characteristics and structure effects of hydrophobic surfaces with micro- and/or nanoscaled structures

We report the drop impact characteristics on four hydrophobic surfaces with different well-scale structures (smooth, nano, micro, and hierarchical micro/nano) and the effects of those structures on the behavior of water drops during impact. The specimens were fabricated using silicon wet etching, black silicon formation, or the combination of these methods. On the surfaces, the microstructures form obstacles to drop spreading and retracting, the nanostructures give extreme water-repellency, and the hierarchical micro/nanostructures facilitate drop fragmentation. The maximum spreading factor (D*(max)) differed among the structures. On the basis of published models of D*(max), we interpret the results of our experiment and suggest reasonable explanations for these differences. Especially, the micro/nanostructures caused instability of the interface between liquid and air at Weber number We > ~80 and impacting drops fragmented at We > ~150.     

生物阴极微生物燃料电池

传统微生物燃料电池(microbial fuel cells,MFCs)主要由生物阳极与非生物阴极组成,属于半生物燃料电池,存在化学药剂再生困难、需要铂等贵金属催化及成本高等缺陷。生物阴极则利用微生物参与阴极反应克服了这些缺陷。微生物参与MFCs阴极反应,最初在海底沉积物MFCs中被发现。为了提高空气-生物阴极的产电效率,人们进行了以铁、锰等过渡金属氧化物修饰电极材料的研究。在厌/缺氧环境中,生物阴极可将硝酸盐和硫酸盐等作为最终电子受体。对生物阴极研究的深入为MFCs工业化应用开辟了道路,此外,本文在文献综述的基础上提出了铁锰联合修饰生物阴极材料的可能性。     

Advances in Graphene/Graphene Composite Based Microbial Fuel/Electrolysis Cells

The modifications of electrodes using graphene and graphene composites in microbial fuel cells (MFCs) and microbial electrolysis cells (MECs) have been widely applied for enhancing the electrochemical catalytic activity and performance of MFCs and MECs. Graphene as one of advanced materials has shown outstanding features for promoting practical applications of MFCs. This review summarizes the modification methods and characterization methods of graphene and related graphene composites on electrode surfaces in MFCs and MECs. The performance improvements of MFCs and MECs by various graphene related composites have been reviewed, which will provide an efficient guide for selecting suitable graphene material to modify electrodes in MFCs and MECs for improving their performance.     

Improved performances of E. coli-catalyzed microbial fuel cells with composite graphite/PTFE anodes

The composite graphite/PTFE electrodes with a variety of PTFE contents were tested as anodes in microbial fuel cell (MFC) based on the biocatalysis of bacteria Escherichia coli (E. coli). It is shown that the PTFE content in the composite electrodes can significantly influence the efficiency of current generation of the MFCs. The composite electrodes with optimized PTFE contents, e.g., 24% to 36% (w/w), are well-suited to serve as anode of E. coli-catalyzed MFCs. In the absence of exogenous electron mediators, E. coli-catalyzed MFC with the composite anode containing 30% PTFE and a conventional air cathode exhibited a power density of 760 mW m⁻², which is even much higher than those reported in the literature so far for E. coli MFCs using efficient electron mediators. These results show significant prospects for developing low cost and effective anode of MFCs.     

Scalable Synthesis of Interconnected Porous Silicon/Carbon Composites by the Rochow Reaction as High‐Performance Anodes of Lithium Ion Batteries

Despite the promising application of porous Si‐based anodes in future Li ion batteries, the large‐scale synthesis of these materials is still a great challenge. A scalable synthesis of porous Si materials is presented by the Rochow reaction, which is commonly used to produce organosilane monomers for synthesizing organosilane products in chemical industry. Commercial Si microparticles reacted with gas CH₃Cl over various Cu‐based catalyst particles to substantially create macropores within the unreacted Si accompanying with carbon deposition to generate porous Si/C composites. Taking advantage of the interconnected porous structure and conductive carbon‐coated layer after simple post treatment, these composites as anodes exhibit high reversible capacity and long cycle life. It is expected that by integrating the organosilane synthesis process and controlling reaction conditions, the manufacture of porous Si‐based anodes on an industrial scale is highly possible.     

Conductive artificial biofilm dramatically enhances bioelectricity production in Shewanella-inoculated microbial fuel cells

A new strategy of electrogen immobilization was developed to construct a conductive artificial biofilm (CAB) on an anode of a microbial fuel cell (MFC). The MFCs equipped with an optimized CAB exhibited an eleven fold increase in power output compared with natural biofilms.     

Effects of different Pt-M (M = Fe,Co, Ni) alloy as cathodic catalyst on the performance of two-chambered microbial fuel cells

For the purpose of reducing the cost and improving the performance of cathodes in microbial fuel cells (MFCs), we prepared Pt/C and Pt-M/C (M = Ni, Co, Fe) electrodes, and characterized them by SEM, XRD and CV. The modified electrodes were used as the cathodes in double-chambered MFCs fed with synthetic medium and molasses sewage respectively. We have found that Pt-M/C catalysts had a better catalytic activity for oxygen reduction than Pt/C in the following order: Pt-Fe/C > Pt-Co/C > Pt-Ni/C > Pt/C. The maximum power density of the MFCs with Pt-M/C cathode was improved by 18–31% compared with the MFC with Pt/C cathode because of the decrease of activation loss in the cathode. This study shows that Pt-M/C catalysts can improve power generation of MFCs without affecting the COD removal and it is proposed that Pt-Fe functions best among the three Pt-M alloys as an efficient and cost-effective catalyst 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.     

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.     

A novel approach for preparation of conductive hybrid elastomeric nano‐composites

Since the discovery of carbon nanotubes (CNTs) and intrinsically conductive polymers, such as polyaniline (PANI) some research has focused on the development of novel hybrid materials by combining CNT and PANI to achieve their complementary properties. Electrically conductive elastomer nano‐composites containing CNT and PANI are described in the present investigation. The synthesis procedure includes in‐situ inverse emulsion polymerization of aniline doped with dodecylbenzene sulfonic acid in the presence of CNT and dissolved styrene‐isoprene‐styrene (SIS) block copolymer, followed by a precipitation–filtration step. The synthesis step is carried out under ultrasonication. The resulting uniform SIS/CNT/PANI dispersions are stable for long time durations. The incorporation of CNT/PANI in the SIS elastomeric matrix improves thermal, mechanical and electrical properties of the nano‐composites. The formation of continuous three‐dimensional CNT/PANI network, assumed to be responsible for enhancement of the resulting nano‐composite properties, is observed by HRSEM. A relatively low percolation threshold of 0.4 wt.% CNT was determined. The Young's modulus of the SIS/CNT/PANI significantly increases in the presence of CNT. High electrical conductivity levels were obtained in the ternary component systems. Copyright © 2013 John Wiley & Sons, Ltd.     

Thermal conductive PS/graphite composites

Polystyrene (PS) was compounded with graphite that possesses high thermal conductivity and layer structures, and the PS/graphite thermal conductive nano‐composites were prepared. Thermal conductivity of PS improved remarkably in the presence of the graphite, and a much higher thermal conductivity of 1.95 W/m K can be achieved for the composite with 34 vol% of colloidal graphite. The Maxwell‐Eucken model and the Agari model were used to evaluate the thermal conductivity of the composites. For the purpose of improving the interfacial compatibility of PS/graphite, realizing the exfoliation and nano‐dispersion of graphite in the PS matrix, three intercalation methods, including rolling intercalation, solvent intercalation, and pan milling intercalation, were applied to prepare the composites, and the morphologies, thermal conductivities, and mechanical properties of the composites were investigated. It should be noted that the one prepared by pan milling intercalation not only had excellent thermal conductivity but also much higher mechanical properties, resulting from a high degree of layer exfoliation of the graphite, the formation of the chain structure agglomerates of the graphite, and the creation of more conductive paths under the strong shear stress of pan milling. Copyright © 2008 John Wiley & Sons, Ltd.     

Effect of nano/micro‐mixed ceramic fillers on the dielectric and thermal properties of epoxy polymer composites

Nano/micro ceramic‐filled epoxy composite materials have been processed with various percentage additions of SiO₂, Al₂O₃ ceramic fillers as reinforcements selected from the nano and micro origin sources. Different types of filler combinations, viz. only nano, only micro, nano/micro, and micro/micro particles, were designed to investigate their influence on the thermal expansion, thermal conductivity, and dielectric properties of epoxy polymers. Thermal expansion studies were conducted using thermomechanical analysis that revealed a two‐step expansion pattern consecutively before and after vitreous transition temperatures. The presence of micro fillers have shown vitreous transition temperature in the range 70–80°C compared with that of nano structured composites in which the same was observed as ~90°C. Similarly, the bulk thermal conductivity is found to increase with increasing percentage of micron‐size Al₂O₃. It was established that the addition of micro fillers lead to epoxy composite materials that exhibited lower thermal expansion and higher thermal conductivity compared with nano fillers. Moreover, nano fillers have a significantly decisive role in having low bulk dielectric permittivity. In this study, epoxy composites with a thermal expansion coefficient of 2.5 × 10^?5/K, thermal conductivity of 1.18 W/m · K and dielectric permittivity in the range 4–5 at 1 kHz have been obtained. The study confirms that although the micro fillers seem to exhibit good thermal conductivity and low expansion coefficient, the nano‐size ceramic fillers are candidate as cofillers for low dielectric permittivity. However, a suitable proportion of nano/micro‐mixed fillers is necessary for achieving epoxy composites with promising thermal conductivity, controlled coefficient of thermal expansion and dielectric permittivity. Copyright © 2013 John Wiley & Sons, Ltd.     

微生物燃料电池

微生物燃料电池 (Microbial Fuel Cells,MFCs) 是一种利用微生物作为催化剂,将燃料中的化学能直接转化为电能的装置。本文首先简要介绍了MFCs 的发展简史和基本原理,针对MFCs 产电性能低的现状,分别从产电微生物、电池结构、质子交换膜(PEM)、电极以及电解液等方面着重综述了近几年有关提高MFCs 产电性能的研究进展。最后介绍了关于MFCs 的另一些有趣的研究方向：植物MFCs,生物阴极MFCs,以及污水脱氮和有毒废水处理。