A high-performance cathode for the next generation of solid-oxide fuel cells

Fuel cells directly and efficiently convert chemical energy to electrical energy. Of the various fuel cell types, solid-oxide fuel cells (SOFCs) combine the benefits of environmentally benign power generation with fuel flexibility. However, the necessity for high operating temperatures (800-1,000 degrees C) has resulted in high costs and materials compatibility challenges. As a consequence, significant effort has been devoted to the development of intermediate-temperature (500-700 degrees C) SOFCs. A key obstacle to reduced-temperature operation of SOFCs is the poor activity of traditional cathode materials for electrochemical reduction of oxygen in this temperature regime. Here we present Ba(0.5)Sr(0.5)Co(0.8)Fe(0.2)O(3-delta)(BSCF) as a new cathode material for reduced-temperature SOFC operation. BSCF, incorporated into a thin-film doped ceria fuel cell, exhibits high power densities (1,010 mW cm(-2) and 402 mW cm(-2) at 600 degrees C and 500 degrees C, respectively) when operated with humidified hydrogen as the fuel and air as the cathode gas. We further demonstrate that BSCF is ideally suited to 'single-chamber' fuel-cell operation, where anode and cathode reactions take place within the same physical chamber. The high power output of BSCF cathodes results from the high rate of oxygen diffusion through the material. By enabling operation at reduced temperatures, BSCF cathodes may result in widespread practical implementation of SOFCs.     

Solid acids as fuel cell electrolytes

Fuel cells are attractive alternatives to combustion engines for electrical power generation because of their very high efficiencies and low pollution levels. Polymer electrolyte membrane fuel cells are generally considered to be the most viable approach for mobile applications. However, these membranes require humid operating conditions, which limit the temperature of operation to less than 100 degrees C; they are also permeable to methanol and hydrogen, which lowers fuel efficiency. Solid, inorganic, acid compounds (or simply, solid acids) such as CsHSO4 and Rb3H(SeO4)2 have been widely studied because of their high proton conductivities and phase-transition behaviour. For fuel-cell applications they offer the advantages of anhydrous proton transport and high-temperature stability (up to 250 degrees C). Until now, however, solid acids have not been considered viable fuel-cell electrolyte alternatives owing to their solubility in water and extreme ductility at raised temperatures (above approximately 125 degrees C). Here we show that a cell made of a CsHSO4 electrolyte membrane (about 1.5 mm thick) operating at 150-160 degrees C in a H2/O2 configuration exhibits promising electrochemical performances: open circuit voltages of 1.11 V and current densities of 44 mA cm-2 at short circuit. Moreover, the solid-acid properties were not affected by exposure to humid atmospheres. Although these initial results show promise for applications, the use of solid acids in fuel cells will require the development of fabrication techniques to reduce electrolyte thickness, and an assessment of possible sulphur reduction following prolonged exposure to hydrogen.     

A class of non-precious metal composite catalysts for fuel cells

Fuel cells, as devices for direct conversion of the chemical energy of a fuel into electricity by electrochemical reactions, are among the key enabling technologies for the transition to a hydrogen-based economy. Of several different types of fuel cells under development today, polymer electrolyte fuel cells (PEFCs) have been recognized as a potential future power source for zero-emission vehicles. However, to become commercially viable, PEFCs have to overcome the barrier of high catalyst cost caused by the exclusive use of platinum and platinum-based catalysts in the fuel-cell electrodes. Here we demonstrate a new class of low-cost (non-precious metal)/(heteroatomic polymer) nanocomposite catalysts for the PEFC cathode, capable of combining high oxygen-reduction activity with good performance durability. Without any optimization, the cobalt-polypyrrole composite catalyst enables power densities of about 0.15 W cm(-2) in H2-O2 fuel cells and displays no signs of performance degradation for more than 100 hours. The results of this study show that heteroatomic polymers can be used not only to stabilize the non-precious metal in the acidic environment of the PEFC cathode but also to generate active sites for oxygen reduction reaction.     

A thermally self-sustained micro solid-oxide fuel-cell stack with high power density

High energy efficiency and energy density, together with rapid refuelling capability, render fuel cells highly attractive for portable power generation. Accordingly, polymer-electrolyte direct-methanol fuel cells are of increasing interest as possible alternatives to Li ion batteries. However, such fuel cells face several design challenges and cannot operate with hydrocarbon fuels of higher energy density. Solid-oxide fuel cells (SOFCs) enable direct use of higher hydrocarbons, but have not been seriously considered for portable applications because of thermal management difficulties at small scales, slow start-up and poor thermal cyclability. Here we demonstrate a thermally self-sustaining micro-SOFC stack with high power output and rapid start-up by using single chamber operation on propane fuel. The catalytic oxidation reactions supply sufficient thermal energy to maintain the fuel cells at 500-600 degrees C. A power output of approximately 350 mW (at 1.0 V) was obtained from a device with a total cathode area of only 1.42 cm2.     

Disruption of extended defects in solid oxide fuel cell anodes for methane oxidation

Point defects largely govern the electrochemical properties of oxides: at low defect concentrations, conductivity increases with concentration; however, at higher concentrations, defect-defect interactions start to dominate. Thus, in searching for electrochemically active materials for fuel cell anodes, high defect concentration is generally avoided. Here we describe an oxide anode formed from lanthanum-substituted strontium titanate (La-SrTiO3) in which we control the oxygen stoichiometry in order to break down the extended defect intergrowth regions and create phases with considerable disordered oxygen defects. We substitute Ti in these phases with Ga and Mn to induce redox activity and allow more flexible coordination. The material demonstrates impressive fuel cell performance using wet hydrogen at 950 degrees C. It is also important for fuel cell technology to achieve efficient electrode operation with different hydrocarbon fuels, although such fuels are more demanding than pure hydrogen. The best anode materials to date--Ni-YSZ (yttria-stabilized zirconia) cermets--suffer some disadvantages related to low tolerance to sulphur, carbon build-up when using hydrocarbon fuels (though device modifications and lower temperature operation can avoid this) and volume instability on redox cycling. Our anode material is very active for methane oxidation at high temperatures, with open circuit voltages in excess of 1.2 V. The materials design concept that we use here could lead to devices that enable more-efficient energy extraction from fossil fuels and carbon-neutral fuels.     

生物质碳在直接碳固体氧化物燃料电池中的应用

研究活性炭和碳化的梧桐叶、橘子皮为直接碳燃料电池燃料时的物化性能和电化学性能.通过X射线衍射研究燃料中碳的形态结构,采用能谱及拉曼研究燃料中元素质量分数.BET测试燃料的比表面积及孔结构.结果表明,碳化的橘子皮燃料中含有钾元素和较高的无定形碳质量分数,有利于碳的Boudouard反应和电化学反应.碳化橘子皮燃料比表面积为74 m2·g-1,且具有较小的孔隙率和较大的堆积密度,与阳极的接触界面较大,作为燃料时,800℃燃料电池最大功率密度可达572.6 mW·cm-2.即非木质、水质量分数大的橘子皮经过高温碳化后得到的生物质碳,作为直接碳燃料燃料电池燃料时,具有优异的性能.      

高能FAE燃料的选择

该文根据对ＦＡＥ燃料的要求,通过比较不同碳氢燃料的物理化学性能,并考虑其它附加因素,选择了可用作ＦＡＥ燃料的碳氢资料,对所选择燃料进行了模拟弹试验,结果发现,采用新燃料后,单位质量燃料形成的云雾体积比以前所用燃料要高得多,从而扩大了云雾区的覆盖面积,也提高了ＦＡＥ的威力。     

代替甲醇作为直接燃料电池燃料的有机物研究进展

发展直接甲醇燃料电池,要面对不少困难,所以有必要寻找其他有机物代替甲醇作为直接醇类燃料电池的燃料．综述了可代替甲醇作为直接醇类燃料电池燃料的有机物,主要有乙醇和多羟基醇．其中乙醇是人们最感兴趣的有机物,是可再生、环保型能源．乙二醇是多羟基醇类中最简单的醇,具有较高的化学能／电能转换率．     

基于MATLAB/Simulink的氢燃料电池系统建模与仿真

车用氢燃料电池在实际应用中易受外界环境和工况变化的影响,存在电压输出不稳定、大滞后性以及燃料安全性等问题,严重阻碍了燃料电池的商业化应用推广.建立更为准确的燃料电池系统模型能够更有效地进行仿真与优化.采用机理建模和辨识建模相结合的方式建立了氢燃料电池系统模型,依据电堆的实际情况建立了输出电压、输出功率的半经验模型;根据燃料电池系统的工作原理,建立了燃料电池空气供给系统和氢气供给系统的机理模型,并在MATLAB/Simulink环境下进行了仿真分析.结果表明:该模型能有效反映电堆运行的工作压力、电堆温度、阴阳极工作压力差以及氧气过量比等关键参数的静、动态变化,进而绘制不同工况下的输出电压、输出功率随负载电流的关系曲线图,从得到的关系曲线图中,得出不同参数的变化对燃料电池运行的影响结果.     

氢能发电及其应用前景

氢能发电系统由氢源、燃料电池和电力变换器及其控制系统组成。随着氢气制备与安全储运技术以及电能变换与控制技术的不断发展和日趋成熟，氢能发电技术即将获得广泛应用，特别是PEMFC发电系统还具有工作温度低，无烟气排放，伪装性能优良，在国防、人防和民用领域都有极高的应用价值。阐述了氢能发电系统的组成及控制系统结构，介绍了燃料电池工作原理、氢气制备方法、储运方式及金属储氢材料的安全性、电力电子变换技术以及氢能发电技术的研究发现状与应用前景。     

H2S气体浓度及流率对复合质子传导膜燃料电池性能的影响

采用溶胶—凝胶法制备了纳米级Li2SO4+Li2WO4+Al2O3复合质子传导膜,研究了不同H2S气体浓度、流率和操作温度对结构为H2S、（复合MoS2阳极催化剂）/ 复合质子传导膜/（复合NiO阴极催化剂）、空气的燃料电池电化学性能影响。燃料电池的性能与通入阳极侧的H2S浓度和流率有关,H2S浓度和流率增加,提高了阳极侧气体扩散速率和电化学活性组分,使燃料电池的开路电压、输出电流与功率密度提高,电化学性能变好。即使气体中的H2S浓度低达5%时,该气体也可作为电池的燃料并用来发电。操作温度增加,质子传导膜的电传导率和电化学反应速率增加,电池的输出电流与功率密度提高。比较了MoS2与复合MoS2催化剂的性能,复合MoS2催化剂比MoS2催化剂具有更好的性能和化学稳定性。当采用纯H2S作为燃料,通入阳极和阴极侧的H2S和空气的流率分别为35mlmin-1和100mlmin-1,操作温度为650、700和750oC时,燃料电池产生的最大功率密度为12.4、52.9和130 mWcm-2、最大电流密度为45、281和350 mAcm-2。     

Materials for fuel-cell technologies.

Fuel cells convert chemical energy directly into electrical energy with high efficiency and low emission of pollutants. However, before fuel-cell technology can gain a significant share of the electrical power market, important issues have to be addressed. These issues include optimal choice of fuel, and the development of alternative materials in the fuel-cell stack. Present fuel-cell prototypes often use materials selected more than 25 years ago. Commercialization aspects, including cost and durability, have revealed inadequacies in some of these materials. Here we summarize recent progress in the search and development of innovative alternative materials.     

降解苯的微生物燃料电池产电性能研究

 通过构建填料型微生物燃料电池（microbial fuel cell,MFC）,对葡萄糖、苯为单一燃料和葡萄糖+苯混合燃料条件下MFC的产电性能及苯的降解效果进行了研究。试验结果表明,1 000 Ω外电阻条件下,以1 500 mg/L葡萄糖作为单一燃料时,MFC可获得的最高功率密度为228 mW/m2（阳极）,相应的体积功率密度为205 W/m3（按阳极室有效体积计算）; 以1 000 mg/L苯作为单一燃料时,最高功率密度为95 mW/m2（阳极）,体积功率密度为09 W/m3;以1 000 mg/L葡萄糖+600 mg/L苯为混合燃料时,最高功率密度为288 mW/m2 (阳极),相应的体积功率密度为259 W/m3。1 000 mg/L葡萄糖+600 mg/L苯混合燃料情况下,MFC在24 h内可将苯完全降解,产电周期结束时MFC的 COD去除率在95%以上。以1 500 mg/L葡萄糖和1 000 mg/L葡萄糖+600 mg/L苯分别作为燃料时,MFC可获得的库仑〖JP2〗效率分别为157%和23%。结果表明,MFC能够利用苯作为燃料,在实现高效降解的同时可稳定地向外输出电能,这为苯类难降解有机物的高效低耗处理提供了新的研究思路。     

固体氧化物燃料电池的系统结构及其研究进展

固体氧化物燃料电池是将燃料中的化学能直接转化为电能的电化学装置,具有高效率、零污染、超静音等特点.本文从原理入手介绍了固体氧化物燃料电池的系统结构和技术发展.     

直接氧化型葡萄糖燃料电池的研制

研究了新型Ｐｔ／Ｃｏ／Ｃ电催化剂的制备,并以其作为阳极制备直接氧化型葡萄糖燃料电池．实验结果证明,葡萄糖燃料电池具有较高的电动势和较优的电极性能,电极稳定性好,不存在毒化问题,是一种有开发前景的燃料电池．     

Nanostructured Electrode Materials for Fuel Cells and Supercapacitors

1 Results Owing to its electrochemical stability, catalytic activity and high electrical conductivity, ruthenium-based oxides have been realized in electrochemistry as excellent electrode materials with applications ranging from electrocatalysts for industrial electrolysis to high power energy storage. Recent studies have suggested that RuOx may have an active role in electrocatalysts for fuel cells.We have been engaged in the fundamental and practical study of nanostructured RuO2-based electrodes[1-5]....     

2022年清洁能源开发热点回眸

2022年清洁能源技术发展的如火如荼，取得了一系列开创性成就，小分子氧化电解水制氢以及CO2电化学还原等技术为“液态阳光”开辟了新路径，电池领域为实现产业化目标寻求新突破。本文评述了“液态阳光”、薄膜太阳能电池、燃料电池、锂电池及生物质能源技术的困境以及在2022年取得的突破性研究进展，并展望了未来清洁能源的发展方向。     

Modeling and Experimental Study of PEM Fuel Cell Transient Response for Automotive Applications

This paper presents an analysis of the dynamic response of a low pressure proton exchange membrane (PEM) fuel cell stack to step changes in load, which are characteristic of automotive fuel cell system applications. The goal is a better understanding of the electrical and electrochemical processes when accounting for the characteristic cell voltage response during transients. The analysis and experiment are based on a low pressure 5 kW proton exchange membrane fuel cell (PEMFC) stack, which is similar to those used in several of Tsinghua's fuel cell buses. The experimental results provide an effective improvement reference for the power train control scheme of the fuel cell buses in Olympic demonstration in Beijing 2008.     

Nanomaterials for renewable hydrogen production, storage and utilization

An ever growing demand for energy coupled with increasing pollution is forcing us to seek environmentally clean alternative energy resources to substitute fossil fuels. The rapid development of nanomaterials has opened up new avenues for the conversion and utilization of renewable energy. This article reviews nanostructured materials designed for selected applications in renewable energy conversion and utilization. The review is based on the authors’ research, with particular focus on solar hydrogen production, hydrogen storage and hydrogen utilization. The topics include photoelectrochemical (PEC) water splitting and photocatalytic hydrogen production, solid-state hydrogen storage, and proton exchange membrane fuel cells (PEMFCs). It is expected that the rational design of nanomaterials could play an important role in achieving a renewable energy based economy in the coming decades.     

直接甲醇燃料电池双极板冷却通道的热设计

将单个直接甲醇燃料电池的固体骨架看成开口系统,燃料电池稳定运行时的热负荷由阳极反应、阴极反应和甲醇直接氧化反应产生的3部分热量组成,利用热力学原理将其计算.在双极板上设置平行的冷却通道,将电池电化学反应产生的热量及时排出,有利于燃料电池的稳定运行.根据燃料电池中燃料、氧化剂的流向和冷却通道内冷却水流向的不同,冷却水和壁面的换热分别在恒热流密度和恒壁温热边界条件下进行.计算了2种情况下冷却通道壁面的温度和换热系数.结果表明,前者的换热效果要比后者好,但是,后者保证了工作层面具有恒定的温度,更有利于直接甲醇燃料电池的稳定运行.