Experimental and Analytical Study of an Anode-Supported Solid Oxide Electrolysis Cell

A 1-D electrochemical model for a solid oxide electrolysis cell (SOEC) is developed and validated using published experimental data. The model combines thermodynamics, kinetic, ohmic, and concentration overpotentials to predict cell performance. For the anode-supported SOEC, good agreement is obtained between the model and experimental data, with ohmic loss being the major contributor to the cell's total overpotential. Both kinetic and concentration losses are less significant due to high-temperature operation. Due to the dominating performance loss, reducing the anode thickness is effective in diminishing the cell potential. Overall, this simple 1-D model can be employed as a design tool to evaluate component design and estimate system performance for industrial applications.     

固体氧化物燃料电池系统及其应用

对固体氧化物燃料电池系统和单体电池及其工作原理、材料组成等作了简要介绍,并介绍了固体氧化物燃料电池在电厂混合发电方面与燃气轮机组成的联合系统技术以及以天然气为燃料家庭热电联产方面的应用。并指出固体氧化物燃料电池由于其高效、环保清洁将是未来能源利用的主要方式。     

Properties and Performance of Cation-Doped Ceria Electrolyte Materials in Solid Oxide Fuel Cell Applications

Cation-doped CeO₂ electrolyte has been evaluated in single-cell and short-stack tests in solid oxide fuel cell environments and applications. These results, along with conductivity measurements, indicate that an ionic transference number of ∼0.75 can be expected at 800°C. Single cells have shown a power density >350 mW/cm². Multicell stacks have demonstrated a peak performance of >100 mW/cm² at 700°C using metallic separators.     

固体氧化物燃料电池堆的稳定工况特性

以大面积电池和千瓦级电堆为对象,研究了温度、燃料成分、流量等对阳极支撑型电堆性能的影响。结果表明:温度的影响最大,复数阻抗谱中高频弧对应的活化能最高;欧姆阻抗的活化能较低,表明其不全是离子电导的电阻,还包括双极板的表面电阻和可能的接触电阻。利用干氢气燃料测试时,在开路电压附近表现出较大的活化极化,且其活化能很小,表明该活化极化的速率控制步骤并非是电荷转移过程,而是对应某种表面扩散过程。模拟重整气燃料测试过程中活化极化不明显,但开路电压较低,性能比氢气燃料差。随着电堆工作电流的增加,燃料尾气的温度增加,表现出明显的热效应。     

Gas Recirculation at the Hydrogen Electrode of Solid Oxide Fuel Cell and Solid Oxide Electrolysis Cell Systems

In this study it is theoretically analyzed how flue gas recirculation at the hydrogen electrode of solid oxide cells (SOC) systems effects fuel utilization and carbon formation. Interdepence between cell fuel utilization, system fuel utilization and gas recirculation is investigated numerically. Tendency towards carbon deposits is evaluated via thermodynamic equilibrium calculations. It is quantified which gas recirculation rates are necessary to achieve high values of system fuel utilization even if the cell fuel utilization is kept at a moderate level. Furthermore, tendency towards carbon deposition strongly depends on temperature, pressure and feed gas composition and can be reduced by adequate recirculation rates. The presented results can be used for the configuration of gas recirculation in SOC systems.     

Microscale Modeling of an Anode‐Supported Planar Solid Oxide Fuel Cell

A microscale model of a solid oxide fuel cell (SOFC) involving the mass transfer together with the electrochemical reaction, the transportation of electrons and ions through the respective spherical shaped electron conducting and ion conducting particles inside the electrodes was mathematically developed. Couples of useful parameters were introduced in order to represent the characteristics of the cell. The predicted cell performance was showed according to various operating and design conditions. The effects of microscale electrode geometry on the cell performance were also taken into account. Parametric study according to the volumetric fraction of ionic and electronic conducting particles was conducted in order to examine the effects of operating conditions on the cell overpotentials. The study results substantiate the fact that SOFC overpotential could be effectively decreased by increasing the operating temperature as well as operating pressure. This present study reveals the working mechanisms of SOFC at the microscale level, while demonstrating the use of microscale relations to enhance the SOFC performance. The accuracy of the presented model was validated by comparing with already existing experimental results from the available literatures.     

固体氧化物燃料电池的研究进展

固体氧化物燃料电池(SOFC)是先进陶瓷材料的一种重要应用,可以通过电化学反应将燃料的化学能直接转换为电能。SOFC具有效率高、性能稳定、便携、低污染等优点,可以实现能源的有效清洁利用。本文结合国内外SOFC的研究情况,分析讨论了SOFC的技术优势、地方产业优势及产业难题,并结合国家政策方面对我国SOFC产业的未来发展做了展望。     

Preparation and Characterization of Samaria-Doped Ceria Electrolyte Materials for Solid Oxide Fuel Cells

The microstructure, thermal expansion, mechanical property, and ionic conductivity of samaria-doped ceria (SDC) prepared by coprecipitation were investigated in this paper. The results revealed that the average particle size ranged from 10.9±0.4 to 13.5±0.5 nm, crystallite dimension varied from 8.6±0.3 to 10.7±0.4 nm, and the specific surface area distribution ranged from 62.6±1.8 to 76.7±2.2 m²/g for SDC powders prepared by coprecipitation. The dependence of lattice parameter, a, versus dopant concentration, x , of Sm³⁺ ion shows that these solid solutions obey Vegard's rule as a ( x )=5.4089+0.10743 x for Ce_{1− x} Sm _x O_{2−1/2 x} . For SDC ceramics sintered at 1500°C for 5 h, the bulk density was over 95% of the theoretical density; the maximum ionic conductivity, σ_800°C=(22.3±1.14) × 10⁻³ S/cm with minimum activation energy, E _a=0.89±0.02 eV, was found in the Ce_0.80Sm_0.20O_1.90 ceramic. A dense Ce_0.8Sm_0.2O_1.9 ceramic with a grain size distribution of 0.5–4 μm can be obtained by controlling the soaking time at 1500°C. When the soaking time was increased, the microhardness of Ce_0.8Sm_0.2O_1.9 ceramic increased, the toughness slightly decreased, which was related to grain growth with the soaking time.     

Fabrication of a Flat Tubular Segmented‐in‐series Solid Oxide Fuel Cell Using Decalcomania Paper

A flat tubular segmented‐in‐series (SIS) solid oxide fuel cell (SOFC) was fabricated using decalcomania paper. The performance of a two‐cell stack with 4.5‐mm‐wide electrodes was investigated in a temperature range of 650–800 °C. The decalcomania paper allowed fabrication of the SIS‐SOFC on all sides of the flat tubular support and achieve an effective electrode area larger than that obtained using typical SOFC fabrication techniques such as screen printing or slurry coating. SEM observations revealed that each component layer was flat, uniformly thick, and well adherent to adjacent layers. Measured values of open circuit voltages were very close to the theoretical values; confirming that the processing technique utilizing decalcomania paper is suitable for SIS‐SOFC fabrication. The power densities of the two‐cell‐stack were 437.4, 375.6, 324.6, and 257.1 mW cm⁻² at 800, 750, 700 and 650 °C, respectively.     

平板式固体氧化物燃料电池的热机械行为

基于COMSOL Multiphysics仿真平台建立了多物理场耦合作用下的平板式固体氧化物燃料单电池模型,考虑多种温度相关的材料物理化学性质,研究了残余应力以及阳极材料中镍体积分数对电池内部热应力的影响.结果表明:残余应力的存在增大了电池关键构件电解质和阴极电极工作状态下的最大拉伸和压缩应力,减小了阳极电极的最大拉伸...     

Phenomenological Theory of Solid Oxide Fuel Cell Anode

We develop a phenomenological theory of oxygen‐ion‐conducting porous cermet anode for solid oxide fuel cells utilizing hydrogen, based on a simple picture of macro‐ and microkinetics of charge and gas transport in the cermet. Its basic equations account for the transport of hydrogen molecules and oxygen anions to the reaction spots, the hydrogen oxidation reaction (whose various mechanisms, including different adsorption stages, are considered) and the water‐product removal. Simple analytical results are obtained for a linear current‐voltage regime, which demonstrate the interplay of these three processes. The nonlinear behavior is analyzed and classified. Various mechanisms of reaction kinetics are considered, subject to three possible mechanisms of water adsorption, in order to specify the law of conversion of ionic current into electronic one. Revealed is the nature of the intermediate quasi‐Tafel regime, in which the anode is usually employed, and of two possible large current regimes: the saturation regime and the blocking regime (due to oxidation of the anode). The study rationalizes principles of anode functioning and builds a basis for a systematic analysis of the effects due to composite structure, that enter through the basic parameters of the theory.     

固体氧化物燃料电池材料的研究进展

本文对燃料电池的研究发展进行了概述,详细地介绍了固体氧化物燃料电池的电解质材料、阴极材料、阳极材料及互连材料,并对固体氧化物燃料电池以后的发展提出了一些建议。     

Development of an Ionic-Conductive Skeletal Structure for an Electrode-Supported Solid Oxide Fuel Cell

A novel ionic-conductive skeletal structure was developed for an electrode-supported solid oxide fuel cell (SOFC). The skeletal structure was formed as an ionic-conductive frame that accumulated two thick porous layers and one dense thin layer. Two types of green sheets were used to form the frame. Thin green sheets (thickness: 15–30 μm) for the dense layers were fabricated with a well-dispersed Gd_0.2Ce_0.8O _x (GDC) slurry and thick sheets (thickness: 150–300 μm) were fabricated with a GDC/pore-former slurry by the tape casting method. Sintering laminated sheets at 1450°C for 8 h in air resulted in an ionic-conductive frame that was suitable for electrode-supported SOFC. The relative density of the inner thin layer, which works as an electrolyte, was higher than 98%, and the outer thick layers remained porous after the sintering. The porous structure of the outer layers was controlled using agglomerated slurries instead of well-dispersed slurries. Electrochemical measurements of the ionic-conductive frame attached with platinum electrodes exhibited potential as high-performance cells.     

固体氧化物燃料电池的热力学及电化学应用基础

固体氧化物燃料电池是一种典型的电化学装置,可以把燃料气和空气（或氧气）的化学能直接转化为电能。电池的整个反应过程可以根据还原剂和氧化剂反应自由焓来进行热力学计算。对于最简单的氢气和氧气的反应来说,可以根据可逆反应平衡方程式计算电池的可逆功,而且SOFC系统和外部环境的热交换也是可逆的。SOFC作为一种伴生热能的发电装置,对热力学的理解必不可少。所以本文将首先介绍一下SOFC的热力学基础,而作为一种电化学发电装置,需要系统了解SOFC的电化学基础,其中重点介绍SOFC的电化学分析曲线——i-V曲线。     

Direct Operation of IP‐Solid Oxide Fuel Cell with Hydrogen and Methane Fuel Mixtures under Current Load Cycle Operating Condition

The effects of methane concentration and current load cycle on the performance and durability of integrated planar solid oxide fuel cell (IP‐SOFC) obtained from Rolls Royce Fuel Cell Systems Ltd (RRFCS) has been investigated. The IP‐SOFC was operated with hydrogen–methane fuel mixture with up to 20% methane concentration at 900 °C for short term operation of the cells with high methane concentration increased the voltage of the IP‐SOFC due to increase in Gibbs free energy. However, it degraded the performance of the IP‐SOFC in long term operation due to carbon deposition on the anode surface. The current load cycle tests were carried out with 95% H₂–5% CH₄ and 80% H₂–20% CH₄ fuel mixtures at 900 °C with a constant current of 1 A. At low methane concentration, the decrease in the IP‐SOFC voltage was observed after operating nine current load cycles (384 h). At higher methane concentration, the voltage of IP‐SOFC decreased by almost 30% just after one current load cycle (48 h) due to faster carbon deposition. So future work is therefore required to identify viable alternative materials and optimum operating conditions.     

Development and Fabrication of a New Concept Planar‐tubular Solid Oxide Fuel Cell (PT‐SOFC)

The paper reports a new concept of planar‐tubular solid oxide fuel cell (PT‐SOFC). Emphasis is on the fabrication of the required complex configuration of Ni‐yttria‐stabilised zirconia (YSZ) porous anode support by tert‐butyl alcohol (TBA) based gelcasting, particularly the effects of solid loading, amounts of monomers and dispersant on the rheological behaviour of suspension, the shrinkage of a wet gelcast green body upon drying, and the properties of final sample after sintering at 1350 °C and reduction from NiO‐YSZ to Ni‐YSZ. The results show that the gelcasting is a powerful method for preparation of the required complex configuration anode support. The anode support resulted from an optimised suspension with the solid loading of 25 vol% has uniform microstructure with 37% porosity, bending strength of 44 MPa and conductivity of 300 S cm^—1 at 700 °C, meeting the requirements for an anode support of SOFC. Based on the as‐prepared anode support, PT‐SOFC single cell of Ni‐YSZ/YSZ/LSCF has been fabricated by slurry coating and co‐sintering technique. The cell peak power density reaches 63, 106 and 141 mW cm^—2 at 700, 750 and 800 °C, respectively, using hydrogen as fuel and ambient air as oxidant.     

Fabrication and Operation of Tubular Segmented‐In‐Series (SIS) Solid Oxide Fuel Cells (SOFC)

A tubular segmented‐in‐series (SIS) solid oxide fuel cell (SOFC) sub module for intermediate temperature (700–800 °C) operation was fabricated and operated in this study. For this purpose, we fabricated porous ceramic supports of 3 YSZ through an extrusion process and analyzed the basic properties of the ceramic support, such as visible microstructure, porosity, and mechanical strength, respectively. After that, we fabricated a tubular SIS SOFC single cell by using dip coating and vacuum slurry coating method in the case of electrode and electrolyte, and obtained at 800 °C a performance of about 400 mW cm^–2. To make a sub module for tubular SIS SOFC, ten tubular SIS SOFC single cells with an effective electrode area of 1.1 cm² were coated onto the surface of the prepared ceramic support and were connected in series by using Ag + glass interconnect between each single cell. The ten‐cell sub module of tubular SIS SOFC showed in 3% humidified H₂ and air at 800 °C a maximum power of ca. 390 mW cm^–2.     

Local Evolution of Triple Phase Boundary in Solid Oxide Fuel Cell Stack After Long‐term Operation

In this research a 100 W solid oxide fuel cells (SOFCs) stack was tested. After 3,700 hours of continuous operation a subsequent post‐test analysis of the anodes' microstructure was conducted using a combination of focused ion beam and scanning electron microscopy. The obtained data was reconstructed into three‐dimensional images, based on which the microstructure parameters were obtained. The microstructure parameters were quantified at nine different locations in the stack. The discussion focuses on tripe phase boundaries as the most important microstructure parameter strongly affecting the anode performance and degradation. The obtained results indicate strong non‐homogeneous microstructure morphology changes after long‐term operation.     

Solid Phase Relations at 950°C in La-Ba-Cu-O

Subsolidus phase relations in the La₂O₃–BaO–CuO system were studied at 950°C. Three previously reported binary compounds exist (La₂CuO₄, BaLa₂O₄, and BaCuO₂) and five previously reported ternary phases occur (La_2-xBa_xCuO_4-(x/2)+δ, La_4-2xBa_2+2xCu_2-xO_10-2x, La_2-xBa_1+xCu₂O_6-(x-2), La_3-xBa_3+xCu₆O_14±δ, and La₄BaCu₅O_13+δ). Of the seven phases in the diagram, all but BaLa₂O₄, BaCuO₂, and La₄BaCu₅O_13+δ were shown to exhibit significant ranges of solubility. The diagram is important in that both >30 K (La_2-xBa_xCuO_4-(x/2)+δ) and >90 K (La_3-xBa_3+xCu₆O_14+δ, x=1) superconductors occur.