燃料电池分布式冷热电联供技术的研究及应用

燃料电池分布式多联供技术(冷热电联供)具有高效、超低废气排放量、低噪声等优点,应用前景广阔。综述了燃料电池分布式冷热电联供技术的研究和应用现状,从技术角度将两种处于优势地位的燃料电池(PEMFC和SOFC)在建筑物中的应用进行了对比分析,并指出了燃料电池分布式多联供技术的研究方向。     

CeO_2基中温复合电解质材料的研究进展

在固体氧化物燃料电池(SOFC)的研究中,实现电池的中温化是近年来研究的热点,而电解质材料在中温范围内的性能优化是实现电池中温化的关键。简述了近年来国内外CeO_2基中温复合电解质材料的研究现状及发展趋势,重点评述了掺杂CeO_2/过渡金属氧化物、掺杂CeO_2/掺杂LaGaO_3、掺杂CeO_2/无机盐以及掺杂CeO_2/Al_2O_3复合电解质为代表的CeO_2基中温复合电解质体系的结构设计、制备、第二相材料对基体电解质材料电化学性能的影响和单电池性能提升的机制,并对复合电解质材料的发展前景进行了展望。     

等离子喷涂-物理气相沉积制备7YSZ纳米结构固体氧化物燃料电池电解质层

氧化钇稳定的氧化锆（YSZ）因其高热稳定性和良好的氧离子电导率被广泛地作为电解质材料应用于固体氧化物燃料电池（SOFC）。常规的平面SOFC电解质制备技术,如带式流延或丝网印刷,需要在1300℃以上的温度下进行烧结,因此采用传统制备技术获得纳米结构电解质层是一个挑战。等离子喷涂-物理气相沉积（PS-PVD）作为一种新技术由于可以实现气相沉积可以提供快速、低成本的方法来制备纳米致密结构电解质层,可避免传统技术在长时间高温烧结引起的材料晶体结构变化以及相邻电极材料间的化学反应。PS-PVD技术具有与传统大气等离子喷涂（APS）完全不同的沉积机制。本研究采用该技术成功地制备了致密的纳米结构7YSZ薄电解质层。当电解质层厚度为8.7～12.3 μm时,其泄露率为2.24～2.29 10-8 cm4gf-1s-1.     

A Novel Ni/YSZ Anode Image Segmentation Method for Solid Oxide Fuel Cell Electrodes Microstructure

For the three‐phase identification of solid oxide cuel cell (SOFC) electrode, this paper presents a novel segmentation method based on gaussian mixture model (GMM) for YSZ/Ni anode optical microscopy (OM) images. A coarseness‐entropy adaptive factor is defined to incorporate the spatial information based on markov random field (MRF) into GMM. Furthermore, the proposed method can obtain the trade‐off between robustness to noise and effectiveness of preserving the details. Experimental results show that the proposed method outperforms the compared method on three‐phase microstructure identification. It can provide reliable foundation for the quantification of SOFC microstructure parameters.     

A three-dimensional heterogeneity analysis of electrochemical energy conversion in SOFC anodes using electron nanotomography and mathematical modeling

In this paper a fully three dimensional, multiphase, micro-scale solid oxide fuel cell anode transport phenomena numerical model is proposed and verified. The Butler-Volmer model was combined with empirical relations for conductivity and diffusivity - notably the Fuller-Shetler-Giddings equation, and the Fickian model for transport of gas reagents. FIB-SEM tomography of a commercial SOFC stack anode was performed and the resulting images were processed to acquire input data. A novel method for estimating local values of Triple Phase Boundary length density for use in a three-phase, three-dimensional numerical mesh was proposed. The model equations are solved using an in-house code and the results were verified by comparison to an analytical solution within the range of its applicability. A limited parametric study was performed to qualitatively assess simulation performance and impact of heterogeneity. Despite the high dependence of the SOFC anode performance on the geometry of its anisotropic, three-phase microstructure there are very few micro-scale numerical models simulating transport phenomena within these electrodes.     

Evaluation of metal-supported solid oxide fuel cells (MS-SOFCs) fabricated at low temperature (∼1,000 °C) using wet chemical coating processes and a catalyst wet impregnation method

The objective of this study is to evaluate metal-supported solid oxide fuel cells fabricated at low temperatures (～1000 °C) in oxidizing environments using wet chemical coating processes and a catalyst impregnation method. Typically, applying general wet chemical coating processes and heat treatment at low temperature is desirable for fabricating metal-supported solid oxide fuel cells when considering manufacturing productivity and efficiency. However, in the case of conventional anodes, a well-organized structure for high performance is rarely formed by sintering at low temperatures when using general fabrication processes. For this reason, a catalyst-impregnated anode is designed and applied to overcome the above issue. First, to evaluate the electrochemical performance of the designed anode, the area-specific resistances of half-cells are investigated. Then, the newly designed anode is applied to a single cell, and microstructural analysis and electrochemical performance measurements are performed. These results confirm that the catalysts are well distributed, that the electrolyte is fully dense and that the electrochemical performances are reasonable. Additionally, the high durability is also verified through a long-term test over 1000 h. Finally, the metal-supported solid oxide fuel cell with a catalyst-impregnated anode fabricated at low temperature is completely validated through the evaluation of a large-size single cell.     

A thermodynamically consistent framework for non-isothermal modelling of local heat generation and electromotive force in SOFC single electrodes

Mathematical models for single electrode reversible heat and non-isothermal electromotive force (EMF) of a solid oxide fuel cell (SOFC) are developed. These models estimate the volumetric reversible heat generation and EMF of electrochemical reactions, within each electrode at local conditions of temperature and pressure, based on entropy change of half reactions. The resulting equations are thermodynamically consistent. They inherently obey the conservation of energy law as the electrochemical energy released added to the heat of reactions at each electrode equate the enthalpy change of the reacted species. The equations are implemented to model electrodes in a tubular micro- solid oxide fuel cell (TμSOFC). The thermodynamic consistency of the model is numerically confirmed as the enthalpy of the reactants equates the electric energy released by the cell plus the sum of electrode heats plus electrolyte Ohmic heat. The effect of thermal gradients on the cell's overall EMF is found to be negligible. The reversible and irreversible heat generation of each electrode are distinguished. Overall, the anode is found to be endothermic, and the cathode exothermic.     

Chemo-mechanical coupling model of solid oxide fuel cell under high-temperature oxidation

Solid oxide fuel cell (SOFC), which is a generation device that converts chemical energy into electrical energy, has been regarded as a new generation device. The diffusion mechanism of metal cations and anions during the high-temperature oxidation process of SOFC is proposed. Based on the equilibrium expression and diffusion equation, the chemo-mechanical coupling relationship between oxide stress and thickness growth of the oxide layer is established by considering the influences of viscoplastic effect and oxide growth effect. The present theoretical result is consistent with the previous experimental results. In addition, the stress critical points corresponding to different parameters are different in initial oxidation stage. The oxide stress varies dramatically with time in the compressive stress phase, but it changes slowly in the tensile stress phase. The compressive stress that exists in the oxide layer increases with the growth coefficient (D_NiO = 1000-15 000 m⁻¹) of the oxide layer. The oxide stresses in oxide layer and electrolyte reduce with viscoplastic coefficient of the oxide layer from J_NiO = 8.97 × 10⁻⁵ Pa⁻¹ s⁻¹ to J_NiO = 16.97 × 10⁻⁵ Pa⁻¹ s⁻¹ and anode-oxide layer thicknesses from H = 30 μm to H = 660 μm, while they increase with viscoplastic coefficient of the anode from J_Ni = 3.81 × 10⁻⁵ Pa⁻¹ s⁻¹ to J_Ni = 12.81 × 10⁻⁵ Pa⁻¹ s⁻¹ and kinetic parabolic constant from k _p = 2.9 × 10⁻¹⁵ m²s⁻¹ to k _p = 12.9 × 10⁻¹⁵ m²s⁻¹ in whole oxidation stage. The oxide thickness increases with kinetic parabolic constant in the whole oxidation stage and this changing trend accords with parabolic diffusion law. The oxide thickness increases with temperatures increasing. The results obtained from this study will provide the reference to the researches of the chemo-mechanical coupling model and performance optimization of SOFC under high-temperature oxidation.     

Aid of a metallic functional layer on Ni/YSZ anode for Direct Methane Fuel Cell

Aid of a metallic overlayer to nickel/yttrium-stabilized-zirconia (Ni/YSZ) anode is investigated in Direct Methane Fuel Cell. Copper modified nickel metallic overlayer shows high activity for fuel cell performance and good stability to coking in methane atmosphere. The copper-nickel overlayer provides advantages of material compatibility with the substrate and catalytic function on copper-modified nickel sites. The results suggest that the overlayer is effective for decomposition of methane and tolerant to coking by removal of deposited carbon via oxidation and gasification reaction.     

An SOFC anode model using TPB-based kinetics

Fundamental studies focusing on the electrode kinetics are essential in understanding the fuel cell operation and optimizing the electrode designs. In this study, we determined the triple-phase boundary (TPB)-based kinetics of hydrogen electrochemical oxidation using nickel patterned electrode experimental data and the Butler-Volmer formalism of the oxidation process. The same kinetics are then incorporated in a cermet electrode electrochemical model to estimate the effective TPB density of the nickel/yittrium-stabilized zirconia cermet anode. The kinetics are found to be of the same order of magnitude as previously determined by the microstructure reconstruction of cermet anode. Simulation results further revealed that the effective TPB density is several orders of magnitude lower than the typically reported physical densities of the cermet anode that possibly suggests that only a minor fraction of the physical TPB is actually required or available to produce the cell current at given cell voltage. The effect of various operating conditions on the anode activation overpotential is also investigated and discussed in this study.