平板式固体氧化物燃料电池多物理场耦合建模

固体氧化物燃料电池(Solid oxide fuel cell,SOFC)在高温下工作,影响电池性能和结构完整性的因素众多,如何能够综合考虑这些因素并准确地预测和优化电池结构与工作性能是亟待解决的问题。使用COMSOL软件建立了单个平板式固体氧化物燃料电池多场耦合有限元三维模型,考虑电化学反应、物质浓度、流体流动、传热和固体力学多物理因素共同作用下,探明了电池在工作阶段的气体摩尔分数、电流密度、温度和热应力的分布规律。结果表明,氢气和氧气的摩尔分数随着气体流动的方向逐渐降低;在电池空气入口处,电解质电流密度较大;电池温度分布不均匀并产生了较大的热应力。本文建立的SOFC多场耦合模型可为后续SOFC的研究提供分析方法和理论支持。     

中温固体氧化物燃料电池的基本性质测量

介绍了固体氧化物燃料电池的工作原理,测量了中温薄膜固体氧化物燃料电池的开路电压、放电曲线及功率曲线,并分析了电池内阻随电流密度的变化.     

直接甲醇燃料电池反应和组分传递的模型计算

本文建立了直接甲醇燃料电池的二维、单相数学模型来研究电池内各种场的分布情况.模型中考虑了与电化学反应相伴随的、与流体动力学相关的反应与物料传递的耦合过程以及甲醇串流对阴极反应的影响;对阳极和阴极催化层传质过程引入了团聚块模型进行修正.计算了电池内的反应组分浓度分布和局部电流分布以及催化层沿长度方向的局部过电势分布,分析丁催化层内反应的非均匀性.在此基础上考察了对电池流场板结构的改进方案:减小集流板肋条宽度以及在肋条过窄时引入金属泡沫代替电池流场板和扩散层对电池性能的影响,通过对比计算表明两种改进均可以使得催化层反应均匀化,使电池输出性能得到提高,后者效果更佳.     

直接甲醇燃料电池两相非等温模型

本文建立了直接甲醇燃料电池的两相、非等温模型.采用多孔介质中的经典多相流动模型来计算电池内与电化学反应相耦合的传质、传热问题;模型中考虑了水的汽化凝结过程和甲醇窜流对电池性能的影响.计算结果表明电池内温度分布不均匀,温度最高点出现在阴极催化层;阳极甲醇浓度分布不均匀是造成阳极催化层内局部反应速率不均匀分布的主要原因,而阴极催化层局部反应速率主要依赖于阴极过电势的分布;大的流场板开口比条件下电池整体均匀性较好,性能得到提高.     

全钒液流电池新型交错蛇型流道研究

本文在传统全钒液流电池交叉型流道和蛇型流道的基础上提出了新型交错蛇型流道。基于全钒液流电池三维瞬态模型模拟结果,总结了新型交错蛇型流道与传统蛇型流道和交叉型流道对电解液渗入量、电解液在电极中分布的均匀性以及泵损失等参数的影响规律。研究结果表明,交错蛇型流道的设计在确保电解液全部渗入和一次性渗入渗出电极的同时也在电极中具有较大的当地速度和反应离子浓度,这些优势使交错蛇型流道的电池性能优于传统交叉型和传统蛇型流道电池。     

考虑空间电荷层效应的氧离子导体电解质内载流子传输特性

晶界或异质界面诱发的空间电荷层(space charge layer,SCL)效应,被认为是氧离子导体电解质内界面附近区域载流子传输特性显著区别于体相区域的关键原因之一.现有研究多采用Poisson-Boltzmann(PB)方程预测SCL效应的影响规律,但其基于载流子电化学平衡假设,无法用于载流子存在宏观运动的工况,极大限制了相关传输机理研究.本文耦合Poisson方程和载流子质量守恒方程,建立了适用于载流子具有宏观运动时氧离子导体内载流子传输过程的模型,推导了控制SCL效应的关键无量纲参数.聚焦固体氧化物燃料电池中常用的AO2-M2O3氧离子导体电解质,对比研究了传统PB方程和本文建立的Poisson-载流子质量守恒耦合方程的预测结果可靠性.进一步采用耦合模型深入分析了考虑SCL效应时氧离子导体内部氧空位传输机理,发现导体界面电流密度增大导致SCL电阻先减小后增大.增大无量纲Debye长度(表征空间电荷层厚度与导体厚度的比值)可显著增大SCL电阻.当驱动氧空位移动的过电势与热势数量级相当时,增大无量纲电势(表征过电势与热势的比值)导致SCL电阻增大;当过电势远小于热势时,改变无量纲电势对氧空位传输过程几乎无影响.本文研究结论可为通过合理设计晶界或异质界面以改善氧离子导体内载流子传输能力及最终提高相关电化学器件性能提供理论依据.     

封面故事

正以金属锂为负极的Li-O_2电池是下一代锂电池的发展方向,其正极催化材料是降低充放电过电势、促进产物Li_2O_2沉积和分解的重要保障。本期封面反映的是由浙江大学材料学院能源材料课题组制备的基于碳布生长的ZnO阵列,为第八届浙江省高校暨浙江大学材料微结     

结合碳捕集的SOFC-sCO2布雷顿循环集成系统性能分析

固体氧化物燃料电池是将化学能转化成电能的全固态能量转换装置,被认为是极具前景的绿色发电系统。本研究提出了结合碳捕集的固体氧化物燃料电池-超临界二氧化碳布雷顿循环集成系统,通过阳极尾气富氧燃烧实现低能耗碳捕集,并利用s CO₂再压缩布雷顿循环回收燃烧室余热提高系统效率。模拟结果显示,该集成系统在设计工况下的净发电效率为59.74%,二氧化碳捕集量为134.50 kg/h。此外,关键工作参数对系统性能的影响分析结果表明,合理的阳极尾气再循环比、燃料利用率和燃料流量是确保系统安全高效运行的必要前提。     

固体氧化物燃料电池体系掺杂氧化锆的理论研究:从结构到导电性（英文）

固体氧化物燃料电池是一种将化学能(如H_2和O_2)转化为电能的清洁能源系统,它具有高效、低碳以及燃料适应性广的特点.作为燃料电池的"心脏",电解质决定了整个电池的性能,其中掺杂氧化锆是最为典型的燃料电池电解质材料.氧化钇稳定氧化锆在高温下具有优良的离子电导率,广泛应用在固体燃料电池中.电解质材料的组成和使用温度对电导率的影响在实验和理论上已得到了充分研究.复合氧化物的原子结构的表征是阐明其导电行为的关键,本文综述了氧化钇稳定氧化锆电解质的结构和导电性研究的最新理论进展,比较了研究该材料所采用的不同的理论方法及其相应结果,并总结了各种方法的优缺点.重点介绍了利用随机表面行走-神经网络方法取得的最新成果,这些成果和实验结果相吻合.结果表明,采用机器学习进行原子模拟为理解固体电解质中遇到的复杂物质现象提供了一种经济、高效和准确的方法.     

分布式微能源网系统集成设计优化研究

分布式冷热电联供是一种多能源综合互补、高效利用的有效方式.本文以广州某2000 m2公寓楼为例构建集"源、储、荷"三位一体的分布式微能源网系统,建立了固体氧化物燃料电池、太阳能集热器等系统关键设备数学模型,基于理想点法优化了系统的集热场面积、热水罐体积、基岩储热容量等关键设计参数,使系统具有最佳的综合性能.结果表明,在...     

CeO2基固体电解质材料研究进展

用稀土或碱土氧化物掺杂的Ce02在较低的温度下(600-800℃)具有较高的氧离子电导率,是用作中低温固体氧化物燃料电池(SOFC)最合适的电解质材料之一。本文综述了近年来对以掺杂的CeO2作电解质的SOFC的性能的研究现状,分析了单掺杂和双掺杂两类情况,并对掺杂时应注意的问题进行了讨论。     

Novel solid acid fuel cell based on a superprotonic conductor Tl3H(SO4)2

We have fabricated a fuel cell based on a superprotonic conductor, a Tl₃H(SO₄)₂ crystal, and have measured the electrical properties of this fuel cell. It is found that the open-circuit voltage in the fuel cell based on the Tl₃H(SO₄)₂ crystal increases by supplying H₂ fuel gas and typically becomes 0.83 V. Moreover, we have observed that the cell voltage decreases with increasing current density, as observed in fuel cells such as proton exchange membrane fuel cell, solid oxide fuel cell, etc. These results indicate that it is possible to use the Tl₃H(SO₄)₂ crystal as the electrolyte of a solid acid fuel cell. In addition, we suggest that the selection of the electrode and the preparation of the very thin electrolyte are extremely important to achieve high-efficiency of power generation of this fuel cell.     

Fabrication of solid-state fuel cell based on DNA film

We have fabricated a fuel cell based on the DNA film (DNAFC) and examined its properties under various humidity conditions at room temperature. The open-circuit voltage of a DNAFC is generated by supplying H₂ gas to the anode. The open-circuit voltage strongly depends on the humidity conditions, and in a DNA film, the optimum condition in which the open-circuit voltage attains a value as high as 0.55 V is achieved under the relative humidity condition of 55%. Furthermore, the cell voltage of the DNAFC decreases with an increase in current density, as observed in fuel cells such as proton exchange membrane fuel cell, solid oxide fuel cell, and several others. These results indicate that DNA film can be used as the fuel cell electrolyte under approximately 55% humidity condition.     

Evaluation of solid electrolyte cells with a versatile electrochemical technique

Voltage losses in fuel cells and other solid electrolyte systems are due to several mass transport and kinetics processes at the electrode/electrolyte interface as well as to ohmic contributions from the electrolyte, electrodes, current collectors and contact resistances. Electrochemical impedance spectroscopy (EIS) has been in use for several decades in fuel cell research and is quite effective in determining the contribution of individual electrode and electrolyte processes. However, data acquisition and analysis can be time-consuming and the technique has many limitations whilst cell performance and operating conditions are varying rapidly with time especially when the cells are under current load. The galvanostatic current interruption (GCI) technique is fast and can be used under a wide range of operating as well as for rapidly varying loads and cell performance conditions. In this paper a totally new and very simple way of adapting commercially available equipment has been described to perform high quality, reliable and fast GCI measurements over a range of different currents in one sequence without having to use an electronic switch or a solid state relay or a separate fast data logging system. Its versatility has been demonstrated with a number of standard RC circuits simulating slow electrode and fast electrolyte processes and by evaluating a number of solid oxide fuel cell materials. The GCI technique has been shown to be able to determine the composition of all standard test circuits within ±1 % of those determined from the EIS technique and actual values of circuit components. The technique has been applied to investigating solid electrolyte cells and produced excellent results.     

Thermal expansion of SOFC materials

A short overview is given for the thermal expansion of solid oxide fuel cell materials. The thermomechanical compatibility of state-of-the-art materials is compared with alternative, new materials. With these alternatives a better adjustment of the thermal expansion coefficients of the various fuel cell components is possible and fuel cells based on the newly developed materials are proposed.     

Mathematical modeling of the operation of SOFC Nickel-cermet anodes

A surface diffusion–reaction model is developed and solved to describe the steady-state operation of Nickel-cermet anodes in solid oxide fuel cells. The model accounts for the migration (backspillover) and diffusion of oxygen ions from the solid electrolyte onto the nickel surface and the concomitant reaction with the fuel over a finite reaction zone extending from the three-phase boundaries onto the Ni–gas interface. The model is developed for various nickel particle geometries and is compared with existing anode model predictions for flat geometries. The performance of the anode, expressed by an anodic effectiveness factor, is found to depend on two dimensionless numbers, which contain all the operational and structural information of the anode. The model is validated with literature experimental data regarding the dependence of the anode performance on the fuel partial pressure and predicts correctly the observed deviation from linearity of the dependence of cell current on fuel partial pressure.     

Measurement of electrode overpotentials for direct hydrocarbon conversion fuel cells

Cathodic and anodic overpotentials were measured using current interruption and AC impedance spectroscopy for two separate solid oxide fuel cells (SOFCs). The fuel cells used yttria-stabilized zirconia (YSZ) as the electrolyte, strontium-doped lanthanum manganite (LSM) as the cathode, and a porous YSZ layer impregnated with copper and ceria as the anode. The Cu/CeO₂/YSZ anode is active for the direct conversion of hydrocarbon fuels. Overpotentials measured using both current interruption and impedance spectroscopy for the fuel cell operating at 700 °C on both hydrogen and n-butane fuels are reported. In addition to providing the first electrode overpotential measurements for direct conversion fuel cells with Cu-based anodes, the results demonstrate that there may be significant uncertainties in measurements of electrode overpotentials for systems where there is a large difference between the characteristic frequencies of the anode and cathode processes and/or complex electrode kinetics.     

Non-conventional solid state fuel cells: Materials & technology

Investigation of “Non-conventional material” for fuel cells, such as oxide-salt-ceramic composites and ceria based or perovskite oxides with different dopants, leads to a much lower fuel cell operating temperature compared to conventional high temperature, ∼1000 °C, solid oxide fuel cells (SOFCs), which provides the new possibilities for facilitating SOFC commercialisation. This work is essentially an effort to develop new types of solid oxide ion and proton fuel cells (SOFC and SPFC) at fairly low temperatures, <800 °C, or intermediate temperature, 400 to 800 °C. The conventional high temperature SOFCs using yttria-stabilised zirconia (YSZ) materials, and low temperature SPFCs (<200 °C) using polymer membrane electrolytes have complex material and system problems from either special high temperature requests or expensive technology and reforming systems. This research is intended to provide materials and technology along new routes for so-called non-conventional fuel cell systems, to facilitate solid state fuel cell cmmercialisation. The fuel cell research on these non-conventional systems is promising. This paper, based on recent achievements in research on materials and technology, summaries the developnt of material systems and new fuel cell devices regarding their potential marketability in the near future. Paper presented at the 3rd Euroconference on Solid State Ionics, Teulada, Sardinia, Italy, Sept. 15–22, 1996     

Oxygen-ion conducting electrolyte materials for solid oxide fuel cells

Oxygen-ion conducting solid electrolyte systems have been reviewed with specific emphasis on their use in solid oxide fuel cells. The relationships between phase assemblage, electrolyte stability and ionic conductivity have been discussed. The role of parameters such as sintering temperature and atmosphere which influence the segregation of impurities, present in the starting ceramic powders, at grain boundaries and at the external surface of the electrolyte compacts has been emphasised. The stability of various electrolyte materials in contact with other fuel cell components and in fuel environments has been discussed in detail. The ageing behaviour at fuel cell operating temperatures has been described. Data on ionic conductivity, mechanical and thermal properties have been presented for a number of electrolyte materials.