Influence of Cathode Modification by Chitosan and Fe^(3+)on the Electrochemical Performance of Marine Sediment Microbial Fuel Cell

The electrochemical performances of cathode play a key role in the marine sediment microbial fuel cells(MSMFCs)as a long lasting power source to drive instruments,especially when the dissolved oxygen concentration is very low in seawater.A CTS-Fe^(3+)modified cathode is prepared here by grafting chitosan(CTS)on a carbon fiber surface and then chelating Fe^(3+)through the coordination process.The electrochemical performance in seawater and the output power of the assembled MSMFCs are both studied.The results show that the exchange current densities of CTS and the CTS-Fe^(3+)group are 5.5 and 6.2 times higher than that of the blank group,respectively.The potential of the CTS-Fe^(3+)modified cathode increases by 138 mV.The output power of the fuel cell(613.0 mW m^(-2))assembled with CTS-Fe^(3+)is 54 times larger than that of the blank group(11.4 mW m^(-2))and the current output corresponding with the maximum power output also increases by 56 times.Due to the valence conversion between Fe^(3+)and Fe^(2+)on the modified cathode,the kinetic activity of the dissolved oxygen reduction is accelerated and the depolarization capability of the cathode is enhanced,resulting higher cell power.On the basis of this study,the new cathode materials will be encouraged to design with the complex of iron ion in natural seawater as the catalysis for oxygen reduction to improve the cell power in deep sea.

Humic Acid and Iron Chelation Modified Anode Improves the Electrochemical Performance of Marine Sediment Microbial Fuel Cell

Marine sediment microbial fuel cell(MSMFCs)can be utilized as a long lasting power source to drive small instruments to work for long time on ocean floor and its higher power has a significant meaning for practical application.Anode modification can greatly improve the performance of MSMFCs.Herein,humic acid(HA)and humic acid-iron ion complex(HA-Fe)were used to modify the anode for constructing a better MSMFCs.The results indicated that HA-Fe modified anode,better than HA modification,significantly improved the MSMFCs cell power output.The maximum power density of HA-Fe modified MSMFCs is 165.3 mW m−2,which are 6.5-folds of blank MSMFCs.The number of microorganisms on anode,redox activity,and relative kinetic activity were 1.8-,6.1-,and 13.1-folds of blank MSMFCs,respectively.The MSMFCs improvement would be attributed to the electron transfer media of HA and the valence conversion of Fe ions.A synergistic interaction between the naturally occurring HA and Fe ions on the anodic surface in marine sediments would make the modified anodes have‘renewable’characteristics,which is beneficial for the MSMFCs to maintain its long-term higher power.

Pyrolyzed Iron Phthalocyanine-Modified Multi-Walled Carbon Nanotubes as Composite Anode in Marine Sediment Microbial Fuel Cells and Its Electrochemical Performance

Improving the performance of anode is a crucial step for increasing output power of marine sediment microbial fuel cells(MSMFCs)to drive marine monitor to work for a long term on the ocean floor.A pyrolyzed iron phthalocyanine modified multi-walled carbon nanotubes composite(FePc/MWCNTs)has been utilized as a novel nodified anode in the MSMFC.Its structure of the composite modified anode and electrochemical performance have been investigated respectively in the paper.There is a substantial improvement in electron-transfer efficiency from the bacteria biofilm to the modified anode via the pyrolyzed FePc/MWCNTs composite based on their cyclic voltammetry(CV)and Tafel curves.The electron transfer kinetic activity of the FePc/MWCNTs-modified anode is 1.86 times higher than of the unmodified anode.The maximum power density of the modified MSMFC was 572.3±14 m W m^-2,which is 2.6 times larger than the unmodified one(218.3±11 m W m^-2).The anodic structure and cell scale would be greatly minimized to obtain the same output power by the modified MSMFC,so that it will make the MSMFC to be easily deployed on the remote ocean floor.Therefore,it would have a great significance for us to design a novel and renewable long term power source.Finally,a novel molecular synergetic mechanism is proposed to elucidate its excellent electrochemical performance.

Performance of low temperature Microbial Fuel Cells(MFCs)catalyzed by mixed bacterial consortia

Microbial Fuel Cells（MFCs） are a promising technology for treating wastewater in a sustainable manner. In potential applications, low temperatures substantially reduce MFC performance. To better understand the effect of temperature and particularly how bioanodes respond to changes in temperature, we investigated the current generation of mixed-culture and pure-culture MFCs at two low temperatures, 10°C and 5°C. The results implied that the mixed-culture MFC sustainably performed better than the pure-culture（Shewanella） MFC at 10°C, but the electrogenic activity of anodic bacteria was substantially reduced at the lower temperature of 5°C. At 10°C, the maximum output voltage generated with the mixed-culture was 540–560 m V, which was 10%–15% higher than that of Shewanella MFCs. The maximum power density reached 465.3 ± 5.8 m W/m^2 for the mixed-culture at10°C, while only 68.7 ± 3.7 m W/m^2 was achieved with the pure-culture. It was shown that the anodic biofilm of the mixed-culture MFC had a lower overpotential and resistance than the pure-culture MFC. Phylogenetic analysis disclosed the prevalence of Geobacter and Pseudomonas rather than Shewanella in the mixed-culture anodic biofilm, which mitigated the increase of resistance or overpotential at low temperatures.

Sulfonated polyaniline/vanadate composite as anode material and its electrochemical property in microbial fuel cells on ocean floor

A unique sulfonated polyaniline/vanadate composite was synthesized and utilized as a composite anode in microbial fuel cells on ocean floor (BMFCs). X-ray diffraction (XRD) and thermogravimetric analysis (TGA) were employed to characterize its chemical composition and morphology. Wettability of the composite anodes decreases due to the addition of polytetrafluoroethylene (PTFE). The electrochemical behavior of the composite anodes was investigated by means of linear sweep voltammetry and Tafel plot measurements. Compared with the plain graphite anode,the composite anode significantly improves the power density,5.5-fold higher,reaching 187.1 mW/m2 and gives a 27-fold higher exchange current density and a higher kinetic activity. A novel synergistic mechanism between sulfonated polyaniline and vanadate is proposed to explain the excellent electrochemical performance. This composite thus has great potential to be used as an anode material for a high-power BMFC.

One-pot pyrolysis route to Fe−N-Doped carbon nanosheets with outstanding electrochemical performance as cathode materials for microbial fuel cell

The naturally lackadaisical kinetics of oxygen reduction reaction(ORR)in the cathode is one of the important factors that restrict the development of air-cathode microbial fuel cells(MFCs).In this work,the iron-nitrogen-carbon hierarchically nanostructured materials had been successfully fabricated by pyrolyzing glucose,iron chloride,and dicyandiamide with the aim of solving the issue.The obtained catalyst with an ultrathin nanostructure demonstrated an idiosyncratic electrocatalytic activity caused by the high content introduction of nitrogen and iron atoms,large surface area,which will offer sufficient active sites for improving the charge/mass transfer and reducing the diffusion resistance.Furthermore,with the increase of N dopant in the catalyst,better ORR catalytic activity could be achieved.Illustrating the N doping was beneficial to the ORR process.The high content of N,BET surface area caused by the N increasing could be responsible for the superior performance according to results of X-Ray photoelectron spectroscopy(XPS),Raman and Brunner-Emmet-Teller(BET)analysis.The ORR on the Fe-N3/C material follows 4e−pathway,and MFCs equipped with Fe-N3/C catalyst achieved a maximum power density(MPD)of 912 mW/m2,which was 1.1 times of the MPD generated by the commercial Pt/C(830 mW/m2).This research not only provided a feasible way for the fabrication of Pt-free catalyst towards oxygen reduction but also proposed potential cathode catalysts for the development of MFCs.

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%.

Electricity generation and brewery wastewater treatment from sequential anode-cathode microbial fuel cell

A sequential anode-cathode double-chamber microbial fuel cell （MFC）, in which the effluent of anode chamber was used as a continuous feed for an aerated cathode chamber, was constructed in this experiment to investigate the performance of brewery wastewater treatment in conjugation with electricity generation. Carbon fiber was used as anode and plain carbon felt with biofilm as cathode. When hydraulic retention time （HRT） was 14.7 h, a relatively high chemical oxygen demand （COD） removal efficiency of 91.7%-95.7% was achieved under long-term stable operation. The MFC displayed an open circuit voltage of 0.434 V and a maximum power density of 830 mW/m^3 at an external resistance of 300 0. To estimate the electrochemical performance of the MFC, electrochemical measurements were carried out and showed that polarization resistance of anode was the major limiting factor in the MFC. Since a high COD removal efficiency was achieved, we conclude that the sequential anode-cathode MFC constructed with bio-cathode in this experiment could provide a new approach for brewery wastewater treatment.

Suppression of Methane Gas Emissions and Analysis of the Electrode Microbial Community in a Sediment-Based Bio-Electrochemical System

The effects of bioelectrochemical systems (BESs) for the suppression of methane gas emissions from sediment were examined using a laboratory-scale reactor system. Methane gas emissions from acetate were suppressed by approximately 36% from control based on the installation of a BES in which carbon-graphite electrodes were buried in sediment and arbitrarily set at certain oxidative potentials (+300 mV vs Ag/AgCl) using a potentiostat. Meanwhile, methane gas emissions increased in the BES reactor where the electrode potential was set at -200 mV. Results obtained from pyrotag sequencing analysis of the microbial community on the surface of the buried electrodes targeting 16S rRNA genes demonstrated that the genusGeobacterhad drastically propagated in a sample from the reactor where the electrodes were buried. Quantitative analysis of 16S rRNA genes of archaea also revealed that the archaeal population had decreased to approximately 1/6 of its original level on the electrode of the BES set at +300 mV. This implied that the oxidation-reduction potential (ORP) in the sediment was raised to the inhibition level for methanogenesis in the vicinity of the buried electrode. Analysis of electron flux in the experiment revealed that electrons intrinsically used for methanogenesis were recovered via current generation in the sediment where a potential of +300 mV was set for the electrode, although most electrons donated from acetate were captured by oxygen respiration and other electron-accepting reactions. These results imply that BES technology is suitable for use as a tool for controlling re-dox-dependent reactions in natural environments, and that it also brought about changes in the microbial population structure and methanogenic activity in sediment.

真菌电化学修复除草剂污染土壤:降解动力学探索

【目的】微生物燃料电池(microbial fuel cell,MFC)在去除污染物的同时产出电能,是一种颇有前景的生态修复手段。构建真菌强化MFC装置,比较电动力(EK)、真菌、MFC修复除草剂污染土壤效果及优缺点,探索MFC在有机污染物修复中的应用潜力。【方法】设计了一种添加真菌进行生物强化的MFC,并用EK、真菌、MFC三种方法修复两种除草剂污染的灭菌土壤。经筛选和驯化的疣孢漆斑菌和踝节菌菌株用于后两种方法,研究真菌强化对MFC去除除草剂的影响。测量土壤pH、电导率、除草剂去除率,MFC产电性能,用气相色谱-质谱鉴定两种除草剂的降解产物。【结果】EK修复中,添加模拟电解液、碳纤维条、加电10 V的处理组7 d后氯氟吡啶酯(F)和高效氟吡甲禾灵(H)去除率分别为71%和38%。真菌、MFC处理F的最大去除率达到100%。对比踝节菌,疣孢漆斑菌对两种除草剂的降解性能更好,疣孢漆斑菌、踝节菌单菌构建的MFC对H的去除率分别为62.5%和24.1%。F降解产物为氟氯吡啶酸,H降解产物为乙酸大茴香酯,推测了降解路径和降解动力学。三种方法降解F以及EK降解H均符合动力学一级反应,而真菌和MFC降解H符合二级反应。【结论】对比EK、真菌修复,MFC修复效果更好,该方法可以较快地修复土壤又无需额外供电,是一种经济有效的自持式修复策略。

海泥孔隙率对海底微生物燃料电池电化学性能影响及有机质扩散分析

海底沉积物微生物燃料电池(MSMFC)在长期运行过程中,海泥孔隙率影响阳极表面水平方向有机质扩散,进而影响阳极电化学性能和电池功率输出.通过人工调节孔隙率在实验室模拟并研究孔隙率对MSMFC的影响,建立孔隙率与MSMFC产电量和水平扩散系数之间定量关系式.结果表明:随着孔隙率升高,阳极动力学活性先降低后升高,最高动力学活性是最低动力学活性的3.85倍;电池最大输出功率密度在孔隙率为45.2%时,达到最大值206.8 mW/m^(2).随着孔隙率的增大,有机质水平扩散系数升高,并与MSMFC产电量存在线性关系.当孔隙率为45.2%时,扩散系数为0.48 m^(2)/s,MSMFC产电量达到804.04 J.该研究结果将为MSMFC在不同海域布放选址、阳极结构设计及电池长期产电运行提供技术支撑.

二氧化锰晶型对MSMFCs阴极电化学性能的影响

海水环境中较低的阴极催化活性严重限制海泥电池(MSMFCs)长期输出功率。碳毡阴极经二氧化锰(MnO_(2))改性可显著提高海泥电池阴极溶氧还原动力学和电化学性能,进而提升电池输出功率。利用水热法合成4种晶型(α、β、γ和δ)MnO_(2)用于海泥电池阴极改性,研究了4种晶型MnO_(2)对海泥电池阴极电化学性能的影响并进行了机理分析。结果表明,与空白对照组相比,4种晶型MnO_(2)均可显著提高阴极抗极化性能、电容性能、交换电流密度和最大输出功率;其中,β-MnO_(2)由于具有高浓度的Mn3+和氧空位,大幅提高了阴极氧还原活性和电化学性能,使比电容最高达846.08 F/m^(2),功率密度最高达700.2 mW/m^(2)。该结果有利于促进设计低溶氧海水条件下海泥电池阴极,进而开发高功率海底原位电源。

改性电极MFC修复除草剂污染土壤初探

微生物燃料电池(MFC)在去除污染物的同时产出电能,是一种颇有前景的生态修复手段。本研究选取研究较少的氟氯吡啶酯和高效氟吡甲禾灵为目标污染物,并通过四步法对石墨毡电极进行改性,构建MFC装置,探索MFC在有机污染物修复中的应用潜力。实验证明,改性电极构建的MFC实验前期发电性能优于未改性电极MFC。相较于氟氯吡啶酯,高效氟吡甲禾灵MFC电导率波动幅度较小,修复温和。修复后期,土壤脱氢酶活性均高于第2天初始值。

4032铝合金活塞在中高温氨水环境中的腐蚀行为研究

近年来,氨(NH_(3))作为内燃机燃料得到广泛关注。氨燃烧会产生大量的水,然而未完全燃烧的氨在有水存在的中高温环境中对发动机活塞部件可能会产生腐蚀。以4032铝合金活塞材料为研究对象,研究其在恒温200℃下25%(质量分数)氨水溶液中的腐蚀行为,着重探讨了在不同时间尺度下铝合金的腐蚀失重、腐蚀产物形态、腐蚀电化学性质。结果表明,4032铝合金在中高温氨水环境中的腐蚀速率随浸泡时间的延长呈先增强后减弱的变化趋势,腐蚀产物主要以Al(OH)_(3)为主。随着浸泡时间的延长,4032铝合金的腐蚀电位Ecorr和极化电阻Rp均逐渐增大,腐蚀电流密度Jcorr逐渐减小,并进一步解析了其腐蚀机理。

碳量子点修饰电极对生物挂膜及硝氮还原特性研究

研究了不同制备条件下的碳量子点(CQDs)修饰碳毡电极对微生物挂膜及硝酸盐氮(NO_(3)^(-)-N)催化还原性能的影响。通过扫描电镜(SEM)和电化学测试方法对其进行测试,结果表明,CQDs质量浓度为14.4 g/L、碳化时间为24 h时,风干干燥方法制备的CQDs修饰电极具有较大的比表面积和良好的挂膜能力;循环伏安曲线分析结果表明,NO_(3)^(-)离子还原峰位于-0.785~-0.663 V之间,峰值电位和峰值电流较大,NO_(3)^(-)-N的还原性能更强,同时交流阻抗谱也体现了该工况下较小的电荷转移内阻,均为10~18Ω之间。因此,使用CQDs修饰可以提升MFC生物阴极的挂膜能力及NO_(3)^(-)-N的催化还原性能。

重整气组分对HT-PEMFC性能影响研究

高温聚合物电解质膜燃料电池(HT-PEMFC)通常以含N_(2)、CO、CO_(2)等非氢组分的重整氢气作为燃料,而非氢组分的存在使得电池性能大幅下降、稳定性变差。通过极化分析、电化学阻抗谱等手段研究了不同组分与浓度的N_(2)、CO对HT-PEMFC性能的影响。结果表明,N_(2)单独存在时的稀释效应增加了物质传输阻抗,而CO单独存在时会毒化电催化剂,增加氢氧化反应(HOR)电荷转移阻抗。在惰性稀释组分和毒化组分共同存在时,膜电极性能损失高于它们单独存在时的加和。该现象源于在较高的H2传质阻力条件下,H_(2)与CO的竞争吸附反应导致的毒化加剧。本研究为HT-PEMFC膜电极的设计优化奠定了基础,并为电堆高效可靠性运行提供指导。

人工湿地-微生物燃料电池系统对十二烷基苯磺酸钠的微生物响应特征

直链烷基苯磺酸盐(LAS)是日化领域应用最为广泛的阴离子表面活性剂,烷基苯磺酸盐及其降解中间产物已经成为环境中常见的代表性有机污染物。本研究以十二烷基苯磺酸钠(SDBS)为目标LAS,通过小试试验探究了人工湿地-微生物燃料电池耦合系统(CW-MFC)对SDBS的处理效果及系统对SDBS的微生物响应特征。结果表明:当进水SDBS浓度为25 mg·L^(-1)时,CWMFC对SDBS的去除率和去除负荷分别为44.3%和6.74 g·m^(-3)·d^(-1);SDBS的加入对CW-MFC系统中微生物群落的组成与活性产生了较大的干扰,微生物需要一定的时间适应并发展SDBS降解能力,而电化学活性菌(EAB)对SDBS的抗性比其他微生物物种更强;SDBS促进了火山岩填料和阳极表面(厌氧环境)的微生物群落丰富度和多样性,而对植物根系和阴极表面(好氧环境)的微生物群落多样性产生了抑制;CW-MFC中火山岩填料表面、阴极表面和阳极表面的优势菌门分别为Proteobacteria、Bacteroidota和Desulfobacteroidota;SDBS将CW-MFC中阳极区EAB(Proteobacteria、Bacteroidota、Firmicutes、Acidobacteriota等)的相对丰度显著提高56.7%,从而提高了CW-MFC的最大输出功率密度并显著降低了系统内阻;CW-MFC中有7个SDBS降解相关菌属,Geobacter可参与β/ω氧化过程,Aeromonas、Acinetobacter和Desulfovibrio可参与脱磺酸过程,Hydrogenophaga、Zoogloea和Dechloromonas可参与苯环裂解过程,其中,Geobacter和Desulfovibrio为厌氧菌属,其余为好氧菌属,此外,火山岩填料表面SDBS降解相关菌属相对丰度最高,占比为61.61%。研究表明,SDBS改变了CW-MFC内部微生物群落的空间分布规律,促进了EAB和SDBS降解相关菌属的富集生长,并改善了CW-MFC的电化学性能。总之,利用CW-MFC系统处理阴离子表面活性剂是可行的。

基于EIS的质子交换膜燃料电池输出性能优化

质子交换膜燃料电池(proton exchange membrane fuel cell, PEMFC)输出性能的影响是多方面的,极化曲线仅能反映燃料电池稳态外输出特性,不能充分反映具体影响因素及规律,因此需研究其内部物理参数的动态变化。通过建立电堆内阻和交流阻抗特性模型,利用电化学交流阻抗谱(electrochemical impedance spectroscopy, EIS)分析不同温度和湿度下燃料电池的内阻动态特性。结果表明,在333~353 K温度范围内,随着温度的增加,燃料电池的内阻减小;当温度不变时,相对湿度的增加能减小电堆内阻,燃料电池输出性能增强。最后,基于15 kW燃料电池测试平台进行性能试验,验证了燃料电池动态特性分析的正确性,为进一步优化PEMFC输出性能提供理论支持。

人工湿地微生物燃料电池构型对低温氨氮去除性能的影响

针对人工湿地在冬季低温条件下氨氮去除率下降的问题,提出构建人工湿地-微生物燃料电池(CW-MFC)的方法来提高人工湿地低温条件下的氨氮去除性能,并考察了CW-MFC构型对低温下氨氮去除性能的影响。120 d的室外连续运行结果表明,在平均气温9.8℃运行60 d,CW-MFC比传统湿地的氨氮去除率提高9.9%。在CW-MFC中添加玻璃纤维作为分隔材料并采用双阳极结构,氨氮平均去除率可以达到81.8%。在CW-MFC产电期间,CW-MFC的容积脱氮效率与输出电压存在较好的相关关系。

中低温固体氧化物燃料电池Ce_(0.9)Gd_(0.1)O_(2-δ)纤维骨架复合阴极的构建与电化学性能研究

为了降低固体氧化物燃料电池(Solid Oxide of Fuel Cell, SOFC)的操作温度,需要将SOFC的阴极催化活性提高,为此,设计和构建了一种SOFC的Ce_(0.9)Gd_(0.1)O_(2-δ)(GDC)纤维骨架复合阴极,最终获得了较低的阴极阻抗。采用溶胶—凝胶法结合静电纺丝制备GDC纤维前驱体,在950℃下煅烧得到一维纳米纤维棒,再与GDC电解质在1450℃下共烧得到孔隙率为70 vol.%孔隙率的纤维骨架。分别采用浸渍LSCF离子溶液和LSCF粉体悬浮液制备出纤维骨架复合阴极,并与传统的LSCF-GDC粉体阴极进行微观结构和电化学性能对比,结果表明制备的纤维骨架复合阴极具有较多的三相界面处,两种骨架阴极的极化阻抗均小于传统阴极极化阻抗。采用弛豫时间分布法分析三种对称电池的极化阻抗,明确了在GDC纤维骨架上浸渍LSCF离子溶液明显提高阴极性能的原因。构造的纤维骨架复合阴极可以克服传统阴极与电解质界面结合活性较差或因晶粒长大导致的阴极三相界面变少的问题,且在550℃~750℃的各个测试温度点,其极化阻抗值均低于传统阴极极化阻抗值约一个数量级,在650℃极化电阻仅为0.050Ω·cm^(2),小于传统复合阴极650℃下的极化阻抗0.280Ω·cm^(2)。因此本研究所获得的阴极是一种可在中低温下使用的SOFC高催化活性纤维骨架复合阴极。