Effect of electrolyte pH on the rate of the anodic and cathodic reactions in an air-cathode microbial fuel cell

The measurement of electricity generation from an air-cathode microbial fuel cell (MFC) with a mixed bacteria culture at different pH showed that this MFC could tolerate an initial (feed solution) pH as high as 10. The optimal initial pH was between 8 and 10 with higher current generation compared to lower or higher pH. The bacterial metabolism exhibited a buffer effect and changed the electrolyte pH. The impedance spectra of the anode and cathode of the MFC at the open-circuit potential (OCP) revealed that the anodic microbial process preferred a neutral pH and microbial activities decreased at higher or lower pH; while the cathodic reaction was improved with increasing pH.     

不锈钢网阴极微生物燃料电池的产电性能研究

构建了一个以曝气池污泥为阳极接种微生物、碳毡为阳极、无任何修饰的不锈钢网为阴极的双室微生物燃料电池. 通过输出电压、功率密度以及电化学阻抗等考察了阴极面积对电池产电性能的影响,并对电池的长期运行稳定性进行评价. 研究结果表明,不锈钢网作为微生物燃料电池的阴极性能稳定. 当不锈钢网面积为2 × 2 cm²时,最大输出电压达到0.411 V,功率密度为0.303 W•m^-2,内阻841 Ω,极化内阻80 Ω. 增大阴极面积至2 × 4 cm²,最大输出电压能达到0.499 V,内阻减小至793 Ω. 不锈钢网价格便宜,具有长期运行稳定性,适宜做MFCs的阴极.     

空气阴极生物燃料电池电化学性能

为提高生物燃料电池(MFC)的输出功率, 降低内阻和有机物处理成本, 实验以空气电极为阴极, 泡沫镍(铁)为阳极,葡萄糖模拟废水为基质构建了直接空气阴极单室生物燃料电池, 考察了电池的电化学性能. 结果表明, MFC的开路电压为0.62 V, 内阻为33.8 Ω, 最大输出功率为700 mW·m-2 (4146 mW·m-3污水), 电子回收率20%. 放电曲线、循环伏安测试表明, MFC首次放电比容量和比能量分别为263 mAh·g-1 COD(化学需氧量)和77.3 mWh·g-1 COD, MFC充放电性能及稳定性均较好. 电化学交流阻抗谱(EIS)分析表明, 随放电时间的延长, 电池阻抗增大, 这是导致电池输出电压逐渐降低的原因之一. MFC运行8 h, COD的去除率为56.5%, 且COD的降解符合表观一级反应动力学.     

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%。     

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.     

生物阴极微生物燃料电池不同阴极材料产电特性

以葡萄糖(COD初始浓度为2000 mg/L, COD为化学需氧量)为阳极燃料底物, 考察了碳纤维刷和柱状活性碳颗粒作为生物阴极微生物燃料电池(MFC)阴极材料的产电性能. 研究结果表明, 碳纤维刷MFC的启动时间比碳颗粒MFC的长, 达到稳定状态后的恒负载(300 Ω)电压(0.324 V)比碳颗粒阴极MFC的(0.581 V)低. 极化分析结果表明, 碳纤维刷MFC和碳颗粒MFC的最大功率密度分别为24.7 W/m3(117.2 A/m3)和50.3 W/m3(167.2 A/m3). 电化学交流阻抗谱(EIS)测定结果表明, 由于电极材料对微生物生长和分布状态存在不同的影响, 使得碳纤维刷阴极MFC的极化内阻大于碳颗粒阴极MFC的极化内阻.     

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.     

Biofuel cell anode based on the Gluconobacter oxydans bacteria cells and 2,6-dichlorophenolindophenol as an electron transport mediator

A basic scheme of the use of the Gluconobacter oxydans bacteria cells as a biocatalyst at an anode of a biofuel cell with air-based cathode is raised up. The anode and cathode of the cell are made of graphite; 2,6-dichlorophenolindophenol serves as an electron transport mediator; and glucose is the substrate to be oxidized. The open-circuit voltage is 55 mV, for the bacteria cell, the mediator, and glucose concentrations of 3 mg/ml (raw weight), 34 mM, and 10 mM, respectively. The voltage and current of the biofuel cell loaded with an external resistance of 10 kohm are 5.6 mV and 0.56 mA. The cell’s internal resistance is 88 kohm.     

中温固体氧化物燃料电池Pr1.2Sr0.8NiO4阴极材料的制备、结构和性能

以相应的氧化物粉末和盐为原料,通过甘氨酸-硝酸盐法合成出了中温固体氧化物燃料电池(IT-SOFC)Pr1.2Sr0.8NiO4(PSNO)阴极原料粉体,并制备出了烧结体试样.采用X射线衍射(XRD)分析对所合成粉体的相组成进行了分析,分别采用热膨胀仪和四端子法对PSNO烧结体试样的热膨胀系数和电导率进行了测定,同时对该阴极材料与Sm0.2Ce0.8O1.9(sco)电解质材料的电化学阻抗谱(EIS)进行了测试分析以SCO作电解质,分别以NiO/SCO和PSNO作阳极和阴极材料,制备出固体氧化物燃料单电池,并对其性能进行测试.实验结果表明,通过甘氨酸-硝酸盐法,在1050℃以上煅烧前驱体,可以获得具有K2NiF4结构的PSNO粉体.所制备的PSNO烧结体试样在200-800℃间的热膨胀系数约为12×10-6 K-1,在450℃下的电导率约为155 S· cm-1,在400-800℃,平均电导活化能为0.034 eV.电化学阻抗谱分析结果表明,在700 ℃下PSNO阴极和SCO电解质间的比表面阻抗(ASR)为0.37Ω·cm2,而Ni-SCO/SCO/PSNO单电池的比表面阻抗为0.61Ω·cm2;所制备的SOFC单电池在800℃下的输出功率为288 mW· cm-2,开路电压为0.75 V.本研究的初步结果表明PSNO 材料是一种综合性能较为优良的新型巾温固体氧化物燃料电池阴极材料.     

Effects of microporous layer preparation on the performance of a direct methanol fuel cell

The effects of two different microporous layer (MPL) preparation methods, including a heated-spraying method and a scraping method, on the performance of a direct methanol fuel cell (DMFC) were investigated. The experimental results indicated the cell with the new MPL had a higher mass transfer rate of oxygen and better performance than that of the conventional MPL. Scanning electron microscopy (SEM) images showed that there were more cracks and voids on the surface of the new MPL than that of the conventional MPL. The cathode and anode polarization curves exhibited that the cell with conventional MPL decreased the cell performance due to the difficulty for mass transport. Electrochemical impedance spectra (EIS) analysis further demonstrated that the improved performance of the cell with new MPL was attributed to the enhanced oxygen transport as the result of the reduced mass transfer resistance in the fuel cell system.     

固体氧化物燃料电池电化学阻抗谱差异化研究方法和分解

电化学阻抗谱技术(EIS)在固体氧化物燃料电池(SOFC)中已获得广泛应用。在EIS分析过程中,研究者能够清楚地获得燃料电池内部因纯离子(电子)导电引起的欧姆电阻和因电化学过程、扩散作用引起的极化阻抗的大小,但是对于极化阻抗的构成缺乏进一步解析。本文选用传统的Ni-YSZ阳极支撑电池,通过改变测试温度、阳极运行气氛和阴极运行气氛,设计了一套完整的阻抗差异分析(ADIS)实验。并基于弛豫时间分布法(DRT)和阻抗差异分析法,系统地分析并解释了阻抗谱中各频率段对应阻抗的物理或(电)化学含义,将该类型电池阻抗谱以6个RQ并联电路予以拟合,为之后燃料电池性能稳定性的研究奠定基础。     

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.     

Single SOFC with Supporting Ni-YSZ Anode,Bilayer YSZ/GDC Film Electrolyte,and La<Subscript>2</Subscript>NiO<Subscript>4 + δ</Subscript> Cathode

Characteristics of fuel cells with supporting Ni-YSZ anode, bilayer YSZ/GDC electrolyte with the thickness of 10 μm, and La₂NiO_{4 + δ} cathode are studied. It is shown that when humid (3% water) hydrogen is supplied to the anode and air is supplied to the cathode, the maximum values of cell’s power density are 1.05 and 0.75 W/cm² at 900 and 800°С, respectively. After the introduction of praseodymium oxide and ceria into the cathode and the anode, respectively, the power density is ca. 1 W/cm² at 700°С. It is found that the power density of a cell with impregnated electrodes weakly increases with the increase in temperature to ca. 1.4 W/cm² at 900°С. The analysis of impedance spectra by the distribution of relaxation times shows that such behavior is associated with the gas-diffusion resistance of the SOFC anode. The latter is explained by the low porosity of the anode and the high rate of fuel consumption.     

Development of novel LSM/GDC composite and electrochemical characterization of LSM/GDC based cathode-supported direct carbon fuel cells

(La_0.8Sr_0.2)_0.95MnO_3?δ (LSM)–Gd_0.1Ce_0.9O_2?δ (gadolinium-doped ceria, GDC) composite cathode material was developed and characterized in terms of chemical stability, sintering behaviour, electrical conductivity, mechanical strength and microstructures to assess its feasibility as cathode support applications in cathode-supported fuel cell configurations. The sintering inhibition effect of LSM, in the presence of GDC, was observed and clearly demonstrated. The mechanical characterization of developed composites revealed that fracture behaviour is directly affected by pore size distribution. The Weibull strength distribution showed that for bimodal pore size distribution, two different fracture rates were present. Furthermore, the contiguity of LSM and GDC grains was calculated with image analysis, and correlation of microstructural features with mechanical and electrical properties was established. Subsequently, an LSM/GDC-based cathode-supported direct carbon fuel cell (DCFC) with Ni/ScSZ (scandia-stabilised zirconia) anode was successfully fabricated via slurry coating and co-firing techniques. The microstructures of electrodes and electrolyte layers were observed to confirm the desired morphology after co-sintering, and a single cell was electrochemically characterized in solid oxide fuel cell (SOFC) and DCFC mode with ambient air as oxidant. The higher values of open-circuit voltage indicated that the electrolyte layer prepared by vacuum slurry coating is dense enough. The corresponding peak power densities at 850 °C were 450 and 225 mW cm^?2 in SOFC and DCFC mode, respectively. Electrochemical impedance spectroscopy was carried out to observe electrode polarization and ohmic resistance.     

A biofuel cell with electrochemically switchable and tunable power output

An electroswitchable and tunable biofuel cell based on the biocatalyzed oxidation of glucose is described. The anode consists of a Cu(2+)-poly(acrylic acid) film on which the redox-relay pyrroloquinoline quinone (PQQ) and the flavin adenine dinucleotide (FAD) cofactor are covalently linked. Apo-glucose oxidase is reconstituted on the FAD sites to yield the glucose oxidase (GOx)-functionalized electrode. The cathode consists of a Cu(2+)-poly(acrylic acid) film that provides the functional interface for the covalent linkage of cytochrome c (Cyt c) that is further linked to cytochrome oxidase (COx). Electrochemical reduction of the Cu(2+)-poly(acrylic acid) films (applied potential -0.5 V vs SCE) associated with the anode and cathode yields the conductive Cu(0)-poly(acrylic acid) matrixes that electrically contact the GOx-electrode and the COx/Cyt c-electrode, respectively. The short-circuit current and open-circuit voltage of the biofuel cell correspond to 105 microA (current density ca. 550 microA cm(-2)) and 120 mV, respectively, and the maximum extracted power from the cell is 4.3 microW at an external loading resistance of 1 kOmega. The electrochemical oxidation of the polymer films associated with the electrodes (applied potential 0.5 V) yields the nonconductive Cu(2+)-poly(acrylic acid) films that completely block the biofuel cell operation. By the cyclic electrochemical reduction and oxidation of the polymer films associated with the anode and cathode between the Cu(0)-poly(acrylic acid) and Cu(2+)-poly(acrylic acid) states, the biofuel cell performance is reversibly switched between "ON" and "OFF" states, respectively. The electrochemical reduction of the Cu(2+)-polymer film to the Cu(0)-polymer film is a slow process (ca. 1000 s) because the formation and aggregation of the Cu(0)-clusters requires the migration of Cu(2+) ions in the polymer film and their reduction at conductive sites. The slow reduction of the Cu(2+)-polymer films allows for the controlling of the content of conductive domains in the films and the tuning of the output power of the biofuel cell. The electron-transfer resistances of the cathodic and anodic processes were characterized by impedance spectroscopy. Also, the overall resistances of the biofuel cell generated by the time-dependent electrochemical reduction process were followed by impedance spectroscopy and correlated with the internal resistances of the cell upon its operation.     

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.     

Single-wall carbon nanotube-based proton exchange membrane assembly for hydrogen fuel cells

A membrane electrode assembly (MEA) for hydrogen fuel cells has been fabricated using single-walled carbon nanotubes (SWCNTs) support and platinum catalyst. Films of SWCNTs and commercial platinum (Pt) black were sequentially cast on a carbon fiber electrode (CFE) using a simple electrophoretic deposition procedure. Scanning electron microscopy and Raman spectroscopy showed that the nanotubes and the platinum retained their nanostructure morphology on the carbon fiber surface. Electrochemical impedance spectroscopy (EIS) revealed that the carbon nanotube-based electrodes exhibited an order of magnitude lower charge-transfer reaction resistance (R(ct)) for the hydrogen evolution reaction (HER) than did the commercial carbon black (CB)-based electrodes. The proton exchange membrane (PEM) assembly fabricated using the CFE/SWCNT/Pt electrodes was evaluated using a fuel cell testing unit operating with H(2) and O(2) as input fuels at 25 and 60 degrees C. The maximum power density obtained using CFE/SWCNT/Pt electrodes as both the anode and the cathode was approximately 20% better than that using the CFE/CB/Pt electrodes.     

Synthesis of LiFePO<Subscript>4</Subscript> nanoparticles and electrochemical studies at full-cell level

LiFePO₄ nanoparticles have been successfully obtained by a solid-phase synthesis method using nanoscaled FePO₄ as starting materials. Three-electrode system using as-prepared LiFePO₄ as cathode was assembled to monitor the variation of voltage and impedance in the anode or cathode. The pouch-typed cells with prepared LiFePO₄ were assembled to investigate electrochemical performance at level of full-cell. The results show that the assembled pouch-typed full-cells present higher power density and favorable cycle life.     

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.     

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。