Improving the efficiency of a direct ethanol fuel cell by a periodic load change

We present a simple method to increase the efficiency of a direct ethanol fuel cell by a periodic modulation of the load (pulsed mode). The fuel cell was periodically short circuited with a resistor (1...     

BLEND MEMBRANES FOR DIRECT METHANOL AND PROTON EXCHANGE MEMBRANE FUEL CELLS

Sulphonated polystyrene ethylene butylene polystyrene(SPSEBS)prepared with 35%sulphonation was found to be highly elastic and enlarged up to 300%-400%of its initial length.It absorbed over 110%of water by weight.A major drawback of this membrane is its poor mechanical properties which are not adequate for use as polymer electrolytes in fuel cells.To overcome this,SPSEBS was blended with poly(vinylidene fluoride)(PVDF),a hydrophobic polymer.The blend membranes showed better mechanical properties than the base polymer.The effect of PVDF content on water uptake,ion exchange capacity and proton conductivity of the blend membranes was investigated.This paper presents the results of recent studies applied to develop an optimized in-house membrane electrode assembly(MEA)preparation technique combining catalyst ink spraying and assembly hot pressing.Easy steps were chosen in this preparation technique in order to simplify the method,aiming at cost reduction.The open circuit voltage for the cell with SPSEBS is 0.980 V which is higher compared to that of the cell with Nafion 117(0.790 V).From this study,it is concluded that a polymer electrolyte membrane suitable for proton exchange membrane fuel cell(PEMFC)and direct methanol fuel cell(DMFC)application can be obtained by blending SPSEBS and PVDF in appropriate proportions.The methanol permeability and selectivity showed a strong influence on DMFC performance.     

Carbon to electricity in a solid oxide fuel cell combined with an internal catalytic gasification process

This study explores strategies to develop highly efficient direct carbon fuel cells (DCFCs) by com‐bining a solid‐oxide fuel cell (SOFC) with a catalyst‐aided carbon‐gasification process. This system employs Cu/CeO2 composites as both anodic electrodes and carbon additives in a cell of the type:carbon|Cu‐CeO2/YSZ/Ag|air. The study investigates the impact on in situ carbon‐gasification and DCFC performance characteristics of catalyst addition and variation in the carrier gas used (inert He versus reactive CO2). The results indicate that cell performance is significantly improved by infusing the catalyst into the carbon feedstock and by employing CO2 as the carrier gas. At 800 °C, the maxi‐mum power output is enhanced by approximately 40% and 230% for carbon/CO2 and car‐bon/catalyst/CO2 systems, respectively, compared with that of the carbon/He configuration. The increase observed when employing the catalyst and CO2 as the carrier gas can be primarily at‐tributed to the pronounced effect of the catalyst on carbon‐gasification through the re‐verse‐Boudouard reaction, and the subsequent in situ electro‐oxidation of CO at the anode three‐phase boundary.     

Preparation and characterization of a new polymer electrolyte (PEO:NaClO3) for battery application

A new sodium-ion conducting thin-film polymer electrolyte based on the poly(ethylene oxide) (PEO) system has been prepared by a solution-casting method. Characterization by XRD, IR, and AC conductivity and Wagner's polarization were carried out on these thin-film electrolytes. From the transference number experiment it was found that the charge transport in these electrolytes is mainly due to ions. Conductivity studies show that the conductivity value of the PEO:NaClO₃ complex increases with the increase of salt concentration. An increase in the conductivity and a change in the cell parameters for the electrolyte system were found by the addition of the low molecular weight dimethylformamide or propylene carbonate as plasticizers. The cell parameters of these electrolyte systems were measured from a discharge study of the cell with the application of a load of 100 kΩ at room temperature in the common cell configuration Na|electrolyte|MnO₂. The open circuit voltage ranges from 2.02 V to 2.46 V and the short circuit current ranges from 570 μA to 1030 μA. Electronic Publication     

Carbon matrix effects on the micro-structure and performance of Pt nanowire cathode prepared by decal transfer method

High performance cathode for polymer electrolyte membrane fuel cell was prepared by depositing Pt nanowires in a carbon matrix coated on a substrate, and using decal transfer method to fabricate the membrane electrode assembly. The effects of carbon and ionomer contents on the electrode micro-structure and fuel cell performance are investigated by physical characterization and single cell testing. The Pt nanowires are gradient distributed across the cathode thickness, and more Pt exists near the membrane. Both the carbon and ionomer contents can affect the Pt nanowires distribution and aggregation. In addition, the carbon loading dominates the transport distance of gas and proton, and the ionomer content affects the triple phase boundaries and porosity in the cathode. The optimal structure of Pt nanowire cathode is obtained at0.10 mg cm-2carbon loading and 10 wt% ionomer.     

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.     

Biofuel cell based on horseradish peroxidase immobilized on copper sulfide as anode for decolorization of anthraquinone AV109 dye

The potential application of electrochemically formed copper sulfide as horseradish peroxidase mediator in the enzymatic biofuel cell and anthraquinone AV109 dye as a fuel is investigated. The open circuit voltage of 0.52 V and short circuit current of ～3.6 μA/cm~2 are obtained, with the maximum specific power of ～1 μW/cm~2. The influence of internal resistance of the cell is discussed. Decolorization is investigated under open circuit potentials, and under external load of 3.3 k conditions. In both cases, 40% of decolorization is achieved, but are three times faster under external load conditions. Specific energy during decolorization in such cell is estimated to ～5 m Wh/m~2. The possible mechanism of the power generation during decolorization of AV 109 dye is discussed.     

Synergistic effect between few layer graphene and carbon nanotube supports for palladium catalyzing electrochemical oxidation of alcohols

Few layer graphene (FLG), multi-walled carbon nanotubes (CNTs) and a nanotube-graphene composite (CNT-FLG) were used as supports for palladium nanoparticles. The catalysts, which were characterized by transmission electron microscopy, Raman spectroscopy and X-ray diffraction, were used as anodes in the electrooxidation of ethanol, ethylene glycol and glycerol in half cells and in passive direct ethanol fuel cells. Upon Pd deposition, a stronger interaction was found to occur between the metal and the nanotube-graphene composite and the particle size was significantly smaller in this material (6.3 nm), comparing with nanotubes and graphene alone (8 and 8.4 nm, respectively). Cyclic voltammetry experiments conducted with Pd/CNT, Pd/FLG and Pd/CNT-FLG in 10 wt% ethanol and 2 M KOH solution, showed high specific currents of 1.48, 2.29 and 2.51 mA μg-1 Pd , respectively. Moreover, the results obtained for ethylene glycol and glycerol oxidation highlighted the excellent electrocatalytic activity of Pd/CNT-FLG in terms of peak current density (up to 3.70 mA μg-1 Pd for ethylene glycol and 1.84 mA μg-1 Pd for glycerol, respectively). Accordingly, Pd/CNT-FLG can be considered as the best performing one among the electrocatalysts ever reported for ethylene glycol oxidation, especially considering the low metal loading used in this work. Direct ethanol fuel cells at room temperature were studied by obtaining power density curves and undertaking galvanostatic experiments. The power density outputs using Pd/CNT, Pd/FLG and Pd/CNT-FLG were 12.1, 16.3 and 18.4 mW cm2 , respectively. A remarkable activity for ethanol electrooxidation was shown by Pd/CNT-FLG anode catalyst. In a constant current experiment, the direct ethanol fuel cell containing Pd/CNT-FLG could continuously deliver 20 mA cm2 for 9.5 h during the conversion of ethanol into acetate of 30%, and the energy released from the cell was about 574 J.     

碱性介质中多孔纳米结构镍/钯-镍电极上甲醇电氧化反应(英文)

A nanostructured Ni/Pd-Ni catalyst with high activity for methanol oxidation in alkaline solution was prepared by electrodeposition followed by galvanic replacement, that is, electrodeposition of Ni-Zn on a Ni coating with subsequent replacement of the Zn by Pd at the open circuit potential in a Pd-containing alkaline solution. The surface morphology and composition of the coatings were examined by energy dispersive X-ray spectroscopy and scanning electron microscopy. The Ni/Pd-Ni coatings were porous and were composed of discrete Pd nanoparticles of about 58 nm. The electrocatalytic activity of the Ni/Pd-Ni electrodes for the oxidation of methanol was examined by cyclic voltammetry and electrochemical impedance spectroscopy. The onset potentials for methanol oxidation on Ni/Pd-Ni were 0.077 V and 0.884 V, which were lower than those for flat Pd and smooth Ni electrodes, respectively. The anodic peak current densities of these electrodes were 4.33 and 8.34 times higher than those of flat Pd (58.4 mA/cm2 vs 13.47 mA/cm2) and smooth Ni (58.4 mA/cm2 vs 7 mA/cm2). The nanostructured Ni/Pd-Ni electrode is a promising catalyst for methanol oxidation in alkaline media for fuel cell application.     

Microwaves spark emission spectroscopy for the analysis of cations:A simple form of atomic emission spectroscopy

A novel method for the cation analysis was investigated.The analysis is based on the sparking of the salts of metals in a microwave oven after placing in a graphite cell.The graphite cell absorbs microwaves and produces high temperature which converts the salt into light emitting species.The colour of light was found to dependent on the nature of cation,however,the intensity of the emitted light was found to be depending upon the form and shape of the graphite assembly in addition to the concentration of the salt.This communication presents explanation for all these observations and for the systematic and quantitative analysis using microwave spark emission technique.     

以丁烷为燃料的便携直接火焰固体氧化物燃料电池堆的研究(英文)

以丁烷液化气为燃料,以固体氧化物燃料电池为电源,可以进行全天候的充电,是未来理想的充电模式。研究了以丁烷为燃料的可以便携的直接火焰燃料电池堆。该电池结构和电性能分别用扫描电子显微镜SEM和电化学工作站进行了表征。该电池堆由3片以Ni/YSZ为阳极支撑形的单电池构成。该电池堆操作开路电压为2.1 V,最大输出功率为0.24 W,可带动小风扇连续运行超过4 h。运行4 h后电池阳极没有积炭发生,说明该电池可以连续运行多个小时,可用作便携充电电源。     

质子交换膜燃料电池阳极抗CO催化剂的研究进展

质子交换膜燃料电池采用重整气或甲醇为燃料时 ,阳极催化剂的CO中毒问题是影响其性能的主要原因 .使用抗CO催化剂是解决该问题的根本方法 .文中对质子交换膜燃料电池的CO问题进行了简介 ,比较详细地介绍了目前抗CO催化剂研究的发展现状 ,包括各种催化剂的活性、制法及抗CO机理 .Mo、W是很有希望改进阳极催化剂抗CO能力的材料 ,多组分催化剂是比较有希望的方向 .     

Two-Layer Fuel Cell Electrolyte Structure by Sol-Gel Processing

Thin layers of yttria-stabilized zirconia (YSZ) at 11 mol% Y₂O₃ doping level was deposited on a sintered disk of Y₂O₃ doped ceria electrolyte by spin-coating from an alkoxide solution. Dense sintered films were obtained by heat-treatment at 600°C. Open circuit voltage (OCV) was measured across the disk in a fuel cell mode with hydrogen fuel on the ceria side and pure oxygen on the YSZ side. Marked improvement of OCV was obtained on the two-layer electrolyte structure with the sol-gel YSZ film.     

固体氧化物燃料电池LSCM-CeO_2/Ni-ScSZ复合阳极制备及性能表征

采用双层流延法制备Ni-ScSZ阳极支撑层-ScSZ电解质复合膜.在烧结的Ni-ScSZ阳极支撑层表面丝网印刷一层LSCM-CeO2阳极催化层,得到LSCM-CeO2/Ni-ScSZ功能梯度层阳极.研究表明,LSCM/CeO2比为1:3(bymass)的功能梯度层阳极Ni-ScSZ13具有较佳的性能.单电池在850℃以H2和乙醇蒸气作燃料的最大功率密度分别为710和669mW/cm2,而LSCM/CeO2为1:0(bymass)的功能梯度层Ni-ScSZ10作阳极的单电池,最大功率密度分别为521和486m W/cm2.两种阳极单电池,分别在700℃于乙醇蒸气中作长时间运行实验,X-射线能量散射分析表明Ni-ScSZ13阳极比Ni-ScSZ10阳极具有较好的抗碳沉积性能.     

新型碳纤维负载直接乙醇燃料电池Pt-SnO_2阳极催化剂的性能研究

采用静电纺丝技术制备了碳纤维基纳米Pt-SnO2阳极催化剂(Pt/Sn原子比为3)。通过X射线衍射(XRD)、红外光谱(FT-IR)、扫描电子显微镜(SEM)等技术对该催化剂进行了表征,并采用循环伏安法对其在乙醇燃料电池中的阳极催化活性进行了评价。结果表明,纳米Pt-SnO2催化剂均匀地分散在碳纤维骨架上;随着烧结温度的升高,碳纤维载体的致密度越高、导电性能越好。电催化性能测试表明,烧结温度为800℃时催化剂的峰电流密度最大,达到0.11 A/cm2,抗中毒能力也最强。单电池的发电性能表明,在一定的乙醇浓度下,1.0 mL/min进样流速具有最优的发电效率。     

固体氧化物燃料电池Cu-LSCM-CeO2/LSCM-YSZ/Ni-ScSZ复合阳极制备及性能

采用流延法制得LSCM-YSZ阳极支撑层/Ni-ScSZ阳极活性层/ScSZ电解质层复合膜,在LSCM-YSZ支撑层上印刷一层Cu-LSCM-CeO₂阳极催化层,即Cu-LSCM-CeO₂/LSCM-YSZ/Ni-ScSZ功能梯度层阳极. 研究表明,Cu/LSCM/CeO₂质量配比为2:7:1功能梯度阳极（LSCM-YSZ2010）有较好的性能,单电池以氢气和乙醇为燃料（750 ^oC）最大功率密度分别为511和390 mW?cm^-2,单电池稳定性实验表明,LSCM-YSZ2010阳极单电池以乙醇为燃料750 ^oC长时间运行218 h,性能稳定. X-射线能量散射分析表明该阳极具有较好的抗碳沉积性能.     

Anode Catalytic Dependency Behavior on Ionomer Content in Direct CO Polymer Electrolyte Membrane Fuel Cell

In this work, the effect of Nafion ionomer content on the structure and catalytic performance of direct CO polymer electrolyte membrane fuel cell(CO-PEMFC) by using Rh-N-C single-atom catalyst as the anode catalyst layers was studied. The ionic plaque and roughness of the anode catalyst layers increase with the increase of Nafion ionomer content. Furthermore, the contact angle measurement results show that the hydrophilicity of the anode catalyst layers also increases with the increase of Nafion ionomer content. However, when the Nafion ionomer content is too low, the binding between microporous layers, catalyst layers and membrane cannot meet the requirement for either electric conductivity or mass transfer. While Nafion ionomer content increased above 30%, the content of water in anode is difficult to control. Therefore, it was found that AN 30(30% Nafion ionomer content of anode) is the best level to effectively extend the three-phase boundary and improve CO-PEMFCs performance.     

Improvement in performance of a direct ethanol fuel cell: Effect of sulfuric acid and Ni-mesh

A direct ethanol fuel cell (DEFC) is developed with low catalyst loading at anode and cathode compared to that reported in the literature. Pt/Ru (40%:20% by wt.)/C and Pt-black were used as anode and cathode catalyst with loadings in the range of 0.5–1.2 mg/cm². The temperatures of anode and cathode were varied from 34 °C to 110 °C, and the pressure was maintained at 1 bar. Although low catalyst loading was used, the cell performance is enhanced by 40–50% with the use of low concentration of sulfuric acid in ethanol and Ni-mesh as current collector at the anode. The power density 15 mW/cm² at 32 mA/cm² of current density is obtained from the single cell with 0.5 mg/cm² loading of Pt–Ru/C at anode (90 °C) and Pt-black at cathode (110 °C). The performance of DEFC increases with the increase in ethanol and sulfuric acid concentrations, electrocatalyst loadings up to 1 mg cm⁻² at anode and cathode. However, the performance of DEFC decreases with further increase in electrocatalyst loading.     

乙醇在Ni-ZnO-ZrO2-YSZ阳极SOFC上的发电性能

为考察乙醇用于固体氧化物燃料电池的可行性,用柠檬酸溶胶 凝胶制备阳极催化材料Ni-ZnO-ZrO₂,利用机械混合法制备Ni-ZnO-ZrO₂-YSZ(Y₂O₃稳定的ZrO₂)阳极。用涂覆法,在YSZ电解质上,制备了Ni-ZnO-ZrO₂-YSZ/YSZ/LSM（La_0.85Sr_0.15MnO₃）与Ni-YSZ/YSZ/LSM的单体电池。在不同蒸发器操作温度、电池操作温度和乙醇蒸气流量下,以乙醇为燃料进行发电实验,对两种阳极的电池发电性能进行比较。实验结束后,用SEM检测了两种电池阳极的表面。结果表明,Ni-ZnO-ZrO₂-YSZ阳极SOFC的电池输出性能明显高于Ni-YSZ阳极,且Ni-ZnO-ZrO₂-YSZ阳极具有较好的抗积炭能力。     

以活性炭为燃料的固体氧化物燃料电池(英文)

采用注浆成型法制备了管状电解质支撑的固体氧化物燃料电池(SOFC),电解质材料为YSZ,阳极和阴极材料都采用银.将活性炭不加任何气体直接用作电池的燃料.电池的有效面积为2.5cm2,在800℃时给出最大功率为16mW,其开路电压随温度的变化与理论结果一致.此电池在30mA的恒电流下连续稳定运行了37h,通过电化学反应消耗了加入电池中碳燃料的42%(w),证明了电池的工作是可以自维持的.与使用石墨燃料的SOFC相比,此电池的运行稳定性得到了明显的提高,因为活性炭比石墨具有大得多的微孔率和表面积.电池运行37h后很快衰减,燃料烧结和燃料量减少造成碳表面积减小可能是衰减的主要原因.电化学阻抗谱测试结果表明电池的极化电阻在电池的总损耗中占主导.通过对电池反应机理进行分析,认为发生在阳极/电解质界面的CO电化学氧化反应和发生在碳燃料表面的Boudouard反应构成的循环维持了电池的运行,因此通过添加促进上述两个反应的催化剂,可提高电池的性能.