Solid Oxide Fuel Cell Electrodes Research Articles

Atomic Layer Deposition for Surface Engineering of Solid Oxide Fuel Cell Electrodes

Atomic layer deposition (ALD) has recently attracted attention as a technique to synthesize and engineer high-performance catalysts and electrodes for fuel cells. Unique advantages of the ALD process include surface conformality and film uniformity along nano-scale features and the ability to deposit one atom layer or less per deposition cycle, enabling atomic-scale modification of the composition and morphology of the material surface. Many recent reports have demonstrated the effectiveness of the ALD surface modification strategy for the development of novel fuel cell materials. For enhancement of fuel cell performance, development of superior electrocatalytic electrodes is essential as a significant portion of energy loss occurs due to the charge transfer reaction either on the surface of electrodes or at the interfaces between electrodes and electrolytes. Therefore, ALD is considered a key fabrication process to design and engineer high-performance fuel cell systems. This review covers the important recent developments advanced electrode materials for solid oxide fuel cells (SOFCs) provided by the unique abilities of ALD for surface engineering and interface modification. Performance enhancement and related mechanisms are also discussed in depth.

Model based evaluation of the electrochemical reaction sites in solid oxide fuel cell electrodes

The electrode microstructure plays an important role in determining the performance of the Solid Oxide Fuel Cells (SOFCs). The conventional SOFC electrodes are based on two kinds of particles, one electron conducting and another ion conducting. Over the years, electrodes with alternative microstructures have been proposed for performance enhancement based on the developments in materials and fabrication techniques. Analytical models for the microstructure offer the scope of quick evaluation of the effect of various microstructural parameters on important microstructural properties like the triple phase boundary densities. However, validation of these models in the light of the experimental data is seldom reported. In this work, the microstructural data derived from image-based reconstruction of the electrodes is used to calibrate and validate an analytical model for the conventional SOFC electrode microstructure revealing insights into the model's applicability. This model forms the basis for the models of other modified microstructures studied in this work. Designing of improved SOFC microstructures require an understanding of the effect of controllable parameters on the reaction sites. Model based evaluation of the electrochemical reaction sites in five different SOFC microstructures is performed in this work. The results and insights will enable the selection of microstructural parameters for tailoring the electrode microstructure to achieve improved performance.

Developing a Coupled Statistical and Monte Carlo Approach for Geometric Modeling and Optimizing of Infiltrated Solid Oxide Fuel Cell Electrode

AbstractThis study proposes a novel geometric simulation methodology to estimate the performance of solid oxide fuel cells (SFOCs) electrodes using Monte‐Carlo approach coupled with a statistical algorithm to add infiltrated particles in the form of discrete voxels. Electrochemical performance of these infiltrated electrodes is then characterized by direct evaluation of triple phase boundary (TPB) density and active surface density of the particles. Study results, in agreement with experiment and analytical models, illustrate that there is an optimum point for particle loading, which is strongly depended on the backbone properties and particle aggregation behavior. Study also indicates that the reduction rate of the gas transport factor after adding particles strongly depends on the backbone porosity and the distribution of the particles. Further, it is shown that the average shape of aggregated particles alters the TPB density and gas transport behavior, but particle agglomeration always increases the surface density of particles. Finally, the geometric results are compared with electrochemical tests qualitatively and proposed theories in literature quantitatively. A case study is also performed to compare geometric properties of a realized model with a real reconstructed infiltrated electrode.

Cation-swapped homogeneous nanoparticles in perovskite oxides for high\xa0power density

Exsolution has been intensively studied in the fields of energy conversion and storage as a method for the preparation of catalytically active and durable metal nanoparticles. Under typical conditions, however, only a limited number of nanoparticles can be exsolved from the host oxides. Herein, we report the preparation of catalytic nanoparticles by selective exsolution through topotactic ion exchange, where deposited Fe guest cations can be exchanged with Co host cations in PrBaMn1.7Co0.3O5+δ. Interestingly, this phenomenon spontaneously yields the host PrBaMn1.7Fe0.3O5+δ, liberating all the Co cations from the host owing to the favorable incorporation energy of Fe into the lattice of the parent host (ΔEincorporation = −0.41 eV) and the cation exchange energy (ΔEexchange = −0.34 eV). Remarkably, the increase in the number of exsolved nanoparticles leads to their improved catalytic activity as a solid oxide fuel cell electrode and in the dry reforming of methane.

Ta-doped PrBa0.94Co2-xTaxO5+δ as promising oxygen electrodes: A focused study on catalytic oxygen reduction reaction activity, stability and CO2-durability

A promising perspective on development of solid oxide fuel cells (SOFCs) is to design a stable oxygen electrode with high catalytic activity toward oxygen reduction reaction (ORR) at reduced temperature. In this study, a series of layered perovskite PrBa0.94Co2-xTaxO5+δ (x = 0–0.04) oxides are systematically studied as oxygen electrodes for intermediate-temperature SOFCs (IT-SOFCs). It is demonstrated that the substitution of Ta5+ for the cobalt ions not only can stabilize the A-site ordered layered structure, but also can improve significantly the catalytic activity for ORR. High electrical conductivity and fast surface oxygen kinetics of the PrBa0.94Co2-xTaxO5+δ cathodes may be responsible for their excellent electrochemical performance. The optimal composition, 2 mol % Ta5+-doped PrBa0.94Co1.96Ta0.04O5+δ, exhibits a lowest polarization resistance (0.020 Ω cm2 at 700 °C). The single cell with the PrBa0.94Co1.96Ta0.04O5+δ cathode delivers a peak power density of 1050 mW cm−2 at 700 °C and is operated steadily at a loading voltage of 0.6 V over 100 h at 650 °C. Furthermore, the PrBa0.94Co1.96Ta0.04O5+δ cathode shows an excellent tolerance to CO2, as evidenced by a durable polarization resistance of 0.061 Ω cm2 at 700 °C in air with 10 vol % CO2.

Stochastic 3D Modeling of Three-Phase Microstructures for Predicting Transport Properties: A Case Study

We compare two conceptually different stochastic microstructure models, i.e., a graph-based model and a pluri-Gaussian model, that have been introduced to model the transport properties of three-phase microstructures occurring, e.g., in solid oxide fuel cell electrodes. Besides comparing both models, we present new results regarding the relationship between model parameters and certain microstructure characteristics. In particular, an analytical expression is obtained for the expected length of triple phase boundary per unit volume in the pluri-Gaussian model. As a case study, we consider 3D image data which show a representative cutout of a solid oxide fuel cell anode obtained by FIB-SEM tomography. The two models are fitted to image data and compared in terms of morphological characteristics (like mean geodesic tortuosity and constrictivity) as well as in terms of effective transport properties. The Stokes flow in the pore phase and effective conductivities in the solid phases are computed numerically for realizations of the two models as well as for the 3D image data using Fourier methods. The local and effective physical responses of the model realizations are compared to those obtained from 3D image data. Finally, we assess the accuracy of the two methods to predict permeability as well as electronic and ionic conductivities of the anode.

High-throughput 3D reconstruction of stochastic heterogeneous microstructures in energy storage materials

Stochastic heterogeneous microstructures are widely applied in structural and functional materials, playing a crucial role in determining their performance. X-ray tomography and focused ion beam serial sectioning are frequently used methods to reconstruct three-dimensional (3D) microstructures, yet are demanding techniques and are resolution-limited. Here, a high-throughput multi-stage 3D reconstruction method via distance correlation functions is developed using a single representatively large-sized 2D micrograph for stochastic microstructures, and verified by X-ray micro-tomography datasets of isotropic and anisotropic solid oxide fuel cell electrodes. This method provides an economic, easy-to-use and high-throughput approach for reconstructing stochastic heterogeneous microstructures for energy conversion and storage devices, and can readily be extended to other materials.

Influence of Initial Powder Morphology on Polarization Characteristics of Nickel/Gadolinium-Doped-Ceria Solid Oxide Fuel Cells Electrode

Nickel-gadolinium doped ceria (Ni-GDC) composite anodes gain a lot of attention as they have potential to be a beneficial solution for the intermediate temperature solid oxide fuel cells. In this paper, the influence of the initial microstructure of Ni-GDC anode on the polarization characteristics and its deterioration in 100h operation are investigated. The initial microstructures of the investigated anodes are determined by the different sizes and aspect ratios of the GDC powders, but all anodes having the same initial compositions of NiO:GDC = 60:40 vol.%. It was found that the anode with the smallest GDC particle had the best initial performance, but also underwent the most severe degradation. The microstructures of the fabricated anodes were investigated by focused ion beam - scanning electron microscopy (FIB-SEM), and microstructural parameters were quantified to relate the electrochemical performance. From the experimentation, contribution of the Ni-GDC microstructure to the anode polarization characteristics is discussed. The morphological evolution after the operation is also in discussion, especially those of the GDC phase. It was concluded that the mobility of GDC could be an influential factor determining the change in polarization resistance.

A Modelling Framework towards Solid Oxide Fuel Cell Electrode Microstructure Optimization

A Modelling Framework towards Solid Oxide Fuel Cell Electrode Microstructure Optimization

Magnetic Alignment of Anode Microstructure in Solid Oxide Fuel Cell

Polarization resistance of solid oxide fuel cell electrodes consists of resistances due to mass transfer and chemical reaction. Therefore, higher ion conductivity, electron conductivity, and gas diffusivity and larger triple-phase boundary (TPB) density lead to lower polarization resistance. To increase effective conductivities and diffusivity, tortuosity factors in each mass-transfer path should be reduced. In this study, magnetic alignment method is developed to align the mass-transfer paths in the electrode microstructure. Since Ni as an electron-conducting material in anode has high magnetic permeability, the particles are polarized and aligned by a magnetic field. Therefore, the tortuosity factors can be reduced. In addition, this Ni alignment is expected to reduce the tortuosity factors of yttria-stabilized zirconia (YSZ) and pore phases as well. However, there is a risk for a decrease in TPB density. The effect of magnetic field on resultant microstructure and polarization resistance of Ni-YSZ anode are investigated by impedance measurement of anode symmetrical cells and by reconstruction of three-dimensional microstructure. The tortuosity factors of Ni and YSZ decreased and TPB density decreased by the magnetic field. As a result, the polarization resistance of anode was kept nearly unchanged. The effect of reducing Ni volume fraction is also investigated.

Electrochemical XPS investigation of metal exsolution on SOFC electrodes: Controlling the electrode oxygen partial pressure in ultra-high-vacuum

Mixed conducting oxides gain increasing interest as anode materials in solid oxide fuel cells (SOFCs), due to their large electrochemically active surface area and excellent redox stability, compared to state-of-the-art Ni-Yttria-Stablilzed Zirconia cermets. However, further optimization of these materials requires more information on the surface chemistry and the reaction mechanisms. Here we present a new concept for electrochemical XPS measurements close to SOFC anode operation conditions even in a UHV chamber. Application of a voltage versus an oxygen buffering reference electrode enables control of the effective oxygen partial pressure in the investigated mixed conducting thin film working electrode within the range that is typical for SOFC anodes or SOEC cathodes. A lower limit is given by the reductive decomposition of the working electrode. The virtual absence of molecules in the gas phase of the UHV chamber largely prohibits presence of atmospheric adsorbates. However, surface oxidation states of metal ions can be tuned by the over potential, and exsolution of metallic species can be monitored in situ. With this technique, we investigated the oxygen partial pressure dependent oxidation states of transition metals in La0.6Sr0.4FeO3-δ, SrTi0.3Fe0.7O3-δ and La0.7Sr0.2Cr0.9Ni0.1O3-δ thin film electrodes. When the oxygen partial pressure in the working electrode goes sufficiently below the NiO/Ni and FeO/Fe redox pairs, the exsolution of metallic Ni or Fe nanoparticles could be monitored in-situ. While most oxides are easier to reduce at the surface, Cr on the La0.7Sr0.2Cr0.9Ni0.1O3-δ surface turns out to be more oxidized than the bulk and can include a Cr6+ species.

Lowering the sintering temperature of solid oxide fuel cell electrolytes by infiltration

A dense electrolyte with a relative density of over 95% is vital to prevent gas leakage and thus the achievement of high open circuit voltage in solid oxide fuel cells (SOFCs). The densification process of ceria based electrolyte requires high temperatures heat treatment (i.e. 1400–1500 °C). Thus, the minimum co-sintering temperatures of the anode-electrode bilayers are fixed at these values, resulting in coarse anode microstructures and consequently poor performance. The main purpose of this study is to densify gadolinia doped ceria (GDC), a common SOFC electrolyte, at temperatures lower than 1400 °C. By this aim, an approach involving the infiltration of polymeric precursors into porous electrolyte scaffolds, a method commonly used for composite SOFC electrodes, is proposed. By infiltrating polymeric precursors of GDC into porous GDC scaffolds, a reduction in the sintering temperature by at least 200 °C is achieved with no additives that might affect the electrical properties. Energy dispersive x-ray spectroscopy line scan analyses performed on porous GDC scaffolds infiltrated by a marker solution (polymeric FeOx precursor in this case) reveals a homogeneous infiltrated phase distribution, demonstrating the effectiveness of polymeric precursors.

Highly sulfur poisoning-tolerant BaCeO3-impregnated La0.6Sr0.4Co0.2Fe0.8O3−δ cathodes for solid oxide fuel cells

Electrochemical performance and sulfur (SO2) tolerance were studied on pristine La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) and BaCeO3-impregnated LSCF (BaCeO3–LSCF) composite cathodes of solid oxide fuel cells (SOFCs). Compared to pristine LSCF electrodes, BaCeO3–LSCF composite electrodes exhibited reduced electrode polarization resistance and significantly lower activation energy for the O2 reduction reaction, indicating that BaCeO2 impregnation is effective at promoting the electrocatalytic activity of LSCF electrodes at low temperatures. Most significantly, BaCeO3–LSCF cathodes show remarkable tolerance and resistance towards sulfur via the formation of BaSO4 instead of SrSO4 on the electrode surface, preventing excess Sr deficiency at the A-site of LSCF perovskite and thus mitigating the sulfur poisoning effect. BaCeO3–LSCF cathodes show potential as highly active and excellent anti-sulfur oxygen electrodes for SOFCs.

AGES: Automated Gas Environment System for in situ neutron powder diffraction.

High fluxes available at modern neutron and synchrotron sources have opened up a wide variety of in situ and operando studies of real processes using scattering techniques. This has allowed the user community to follow chemistry in the beam, which often requires high temperatures, gas flow, etc. In this paper, we describe an integrated gas handling system for the general-purpose powder diffraction beamline Powgen at the Spallation Neutron Source. The Automated Gas Environment System (AGES) allows control of both gas flow and temperature (room temperature to 850 °C), while measuring the partial pressure of oxygen and following the effluent gas by mass spectrometry, concurrent with neutron powder diffraction, in order to follow the structural evolution of materials under these conditions. The versatility of AGES is illustrated by two examples of experiments conducted with the system. In solid oxide fuel cell electrode materials, oxygen transport pathways in double perovskites PrBaCo2O5+δ and NdBaCo2O5+δ were elucidated by neutron diffraction measurements under atmosphere with oxygen partial pressures (pO2) of 10-1 to 10-4 (achieved using mixtures of nitrogen and oxygen) and temperatures from 575 to 850 °C. In another example, the potential oxygen storage material La1-xSrxFeO3 was measured under alternating flows of 15% CH4 in N2 and air (20% O2 in N2) at temperatures from 135 to 835 °C. From the oxygen stoichiometry, the optimal composition for oxygen storage was determined.

In Situ and Surface-Enhanced Raman Spectroscopy Study of Electrode Materials in Solid Oxide Fuel Cells

Solid oxide fuel cells (SOFCs) represent next-generation energy sources with high energy conversion efficiencies, low pollutant emissions, good flexibility with a wide variety of fuels, and excellent modularity suitable for distributed power generation. As an electrochemical energy conversion device, the SOFC’s performance and reliability depend sensitively on the catalytic activity and stability of electrode materials. To date, however, the development of electrode materials and microstructures is still based largely on trial-and-error methods because of the inadequate understanding of electrode process mechanisms. Therefore, the identification of key descriptors/properties for electrode materials or functional heterogeneous interfaces, especially under in situ/operando conditions, may provide guidance for the design of optimal electrode materials and microstructures. Here, Raman spectroscopy is ideally suited for the probing and mapping of chemical species present on electrode surfaces under operating conditions. And to boost the sensitivity toward electrode surface species, the surface-enhanced Raman spectroscopy (SERS) technique can be employed, in which thermally robust SERS probes (e.g., Ag@SiO2 core–shell nanoparticles) are designed to make in situ/operando analysis possible. This review summarizes recent progresses in the investigation of SOFC electrode materials through Raman spectroscopic techniques, including topics of early stage carbon deposition (coking), coking-resistant anode modification, sulfur poisoning, and cathode degradation. In addition, future perspectives for utilizing the in situ/operando SERS for investigations of other electrochemical surfaces and interfaces are also discussed.

Frequency-Resolved Evaluation of Electrode Oxidation State in La0.6Sr0.4CoO3 Thin Films with Operando XAS

Commercial adoption and implementation of renewable, but intermittent, energy sources relies on a new generation of high-performance energy conversion and storage devices, such as solid oxide fuel cells (SOFC) and solid oxide electrolysis cells (SOEC). Performance of the oxygen electrode in SOFC is a limiting factor; however, improvements are hindered by inadequate understanding of electrochemical reaction and ionic diffusion processes. AC impedance and DC polarization techniques are typically used to infer relationships between driving energy and reaction rate, but uniquely understanding reaction mechanisms without direct chemical state measurements of the electrode is challenging. In recent years, workers have developed in operando X-ray absorption spectroscopy (XAS) to study oxygen chemical potentials in SOFC cathodes under operating temperatures and Po2. Determining the oxygen chemical potential is based on shifts in the X-ray absorption edge of 3d transition metals due to valence changes to compensate for oxygen vacancies. So far, operando XAS has only been measured under DC polarization, and thus lacked the ability to probe processes of different timescales [1]. In this work, we extend operando XAS to AC impedance measurements, allowing direct frequency-resolved measurement of electrode oxidation state. This approach can potentially be applied to nonlinear harmonic responses, and the first step in the spatially-resolved mapping of the local steady-periodic electrode response. A dense film of La0.6Sr0.4CoO3 (LSC) was deposited on a mirror polished Gd-doped ceria pellet by pulsed laser deposition as the working electrode with porous Pt counter and reference electrodes. Absorption spectra of the Co K-­edge were collected from fluorescent X-rays to determine the detection energy most sensitive to changes in Co valence state. Operando XAS measurements were conducted at 973 K in 10% O2 at the predetermined X-ray energy, typically around 7.718 keV, under electrical perturbations large enough to excite moderate nonlinearity. The frequency resolved oxidation state response of the electrode is obtained by converting X-ray absorption data to oxygen chemical potentials via sets of calibration XAS spectra at various effective Po2. As a result, the data can be treated by the same analysis methods developed for the voltage response in AC impedance measurements.

Novel Processing of Cathodes for Solid Oxide Fuel Cells

Solid-oxide fuel cells (SOFCs) are electrochemical devices that efficiently convert chemical energy of fuels into electricity.[1] However, they typically operate at high temperature (800–1000 °C) causing substantial challenges in cost and material compatibility. SOFC that can work at intermediate temperature (IT) (500–750 °C) is thus more attractive.[2] SOFC is generally composed of anode, electrolyte and cathode. A practical cathode for SOFCs should possess sufficiently high thermo-mechanical stability, good thermal and chemical compatibility with the electrolyte, high chemical stability against the surrounding atmosphere, good electro-catalytic activity for oxygen reduction reaction (ORR), as well as high electrical conductivity.[1] However, the current widely used cathode, lanthanum strontium manganite (LSM), rapidly loses activity below 800 °C.[3] According to numerical calculations, the efforts to optimize the oxygen surface exchange reaction are required while very high ionic conductivities are not necessary in order to achieve the goal of a highly active cathode.[4] Nano-sized palladium (Pd) and platinum (Pt) show very high activity towards oxygen activation, which can substantially increase the cathode electrochemical performance by improving the surface properties. However, precious metals are expensive and undergo sintering. Silver is a good alternative for its relatively low price and high electrocatalytic activity for oxygen activation, however more easily sintered than Pt and Pd resulting in the electrode deactivation.[5] As the electrodes and the dense electrolyte are sintered together in SOFC, the deactivated electrodes are normally neither regenerable nor replaceable, what brings the end of the SOFC. On the other hand, the Ag-doped perovskites have promoted catalytic oxidation of CO, CH4, n-hexane, and NO,[6] which was significantly improved by the partial substitution of Ag into the A-site of perovskite together with the additional formation of the oxygen vacancy and the metallic Ag on the surface of the perovskite forming composite materials. [7, 8] Among several ways to process the composites, infiltration has shown promising results bringing the possibility to tailor electronic, ionic and mixed ionic electronic conductivities in a porous backbone of proton conducting oxides. [9, 10] The exsolution of nickel, ruthenium, silver or other metal nanoparticles has been investigated in reducing conditions for the design of the electrodes for SOFC. [11-13] The development of highly electrochemically active cathodes for SOFCs requires the optimization of materials composition together with micro- and nanostructures in order to form stable and catalytically active composite electrodes. Here we report on the novel heterostructured silver nanoparticle-decorated perovskite composites La0.95-xSrxMn1-y-z(Fe,Ni,Zn,Mg)zNbyO3-δ – 0.05Ag (exLSAMN) as highly active and durable cathodes for SOFCs, derived from single phase La0.95-xSrxAg0.05Mn1-y-z(Fe,Ni,Zn,Mg)zNbyO3-δ (LSAMN) perovskite precursors through an exsolution process. We report LSAMN as a novel precursor which can develop into high-performance nanosized silver modified LSM-based electrode under cathodic polarization or reducing atmosphere with improved stability and in situ electrochemical regeneration capability. The LSAMN materials were synthesized by solid state reaction and wet chemical synthesis method in order to compare the activity. The electrochemical intercalation/de-intercalation of metal catalysts is a conceptually attractive approach that is also applicable for the development of other metal-modified oxide electrodes. The composite formation and properties were tailored by changing the synthesis route and thermal treatment. A thorough description of the synthesis methods is presented as well as a careful characterization of the microstructure and phase composition of the resulting composite electrodes. The performance of the new composite cathodes with gadolinia-doped ceria (CGO) electrolyte is demonstrated. The exLSAMN electrode showed fairly high electrochemical activity and low area specific resistance (ASR). These unique features make the new materials highly promising cathodes for SOFCs at intermediate temperatures. References A. B. Stambouli, E. Traversa, Renew. Sust. Ener. Rev., 6 (2002) 433.J. A. Kilner, M. Burriel, Ann. Rev. Materi. Res., 44 (2014) 365.S. P. Jiang, J. Mater. Sci., 43 (2008) 6799.J. Fleig, J. Pow. Sour., 105 (2002) 228.T. Z. Sholklapper et al. J. Pow. Sour., 175 (2008) 206.D. Y. Yoon et al. J. Catal., 319 (2014) 182.K. Wang et al. Catalysis Today, 158 (2010) 423.G. Pecchi et al. App. Catalysis A: General, 371 (2009) 78.C. Duan et al. Science, 349 (2015) 1321.C. Duan et al. Energy Environ. Sci., 10 (2017) 176.Y. Zhu et al. Nano Lett., 16 (2016) 512.J. T. S. Irvine et al. Nature Energy, 1 (2016) 15014.G. Tsekouras, D. Neagu, J. T. S. Irvine, Energy Environ. Sci., 6 (2013) 256.

Three phases segmentation from Ni/YSZ anode optical microscopy images using quantum-inspired mixture clustering model

Three-phase segmentation of solid oxide fuel cell (SOFC) anode image is essential for its microstructure quantitative analysis. A quantum-inspired mixture clustering model is developed for Ni/YSZ anode optical microscopy (OM) images. The proposed mixture clustering model focuses on combining Markov random field (MRF)-based fuzzy logic model with Gaussian mixture model (GMM). In the premise part of fuzzy if-then rules, the clique potential MRF function is defined by multiplication of both prior distributions and fuzzy membership functions with a quantum-inspired adaptive fuzzy degree, which takes prior statistics properties and spatial contextual information of SOFC anode OM image into consideration. In addition, GMM is introduced into the consequent part to design a negative log-prior function as the pixel distance metric. The proposed method has been compared to other state-of-the-art segmentation algorithms on both simulated images and real SOFC anode OM images. The experimental results demonstrate that the proposed method is able to achieve a higher segmentation accuracy with a faster convergence speed, which lays firm foundation for microstructural parameters extraction from SOFC electrodes image datasets.

Evaluation of PrNi0.4Fe0.6O3-δ as a symmetrical SOFC electrode material

Symmetrical Solid Oxide Fuel Cell has identical electrode material on both electrodes, of which the most outstanding advantage is the ability to remove the deposited carbon and other deposits from anode. Owing to the working conditions of electrodes, there are more requirements for electrode materials than normal ones. In this study, we evaluate the traditional cathode material PrNi0.4Fe0.6O3-δ as a symmetrical solid oxide fuel cell electrode material. Unstable as most traditional cathode materials are in fuel gas, however, the result here exhibits PrNi0.4Fe0.6O3-δ has good performance. The peak power density of the cell with PrNi0.4Fe0.6O3-δ electrode in wet methane at 800 °C is 663 mWcm−2 with observable decomposition on anode. After switching the fuel gas on anode to air, the structure recovers quickly. In terms of the recyclable performance, PrNi0.4Fe0.6O3-δ seems suitable for symmetrical solid oxide fuel cell.

A numerical study of infiltrated solid oxide fuel cell electrode with dual‐phase backbone

Three-dimensional microstructure of infiltrated solid oxide fuel cell electrodes with dual-phase backbone is simulated numerically. This work employs LSM (lanthanum strontium manganite) infiltrated LSM yttria-stabilized zirconia composite electrodes as an example. Important geometric properties, including percolation probability of LSM, total and percolated three-phase boundary (TPB) lengths, and total and percolated surface areas of LSM, are calculated under various LSM nanoparticle loadings. One important finding is that compared with pure yttria-stabilized zirconia backbone, dual-phase backbone results in lower TPB length and has little impact on the surface area of LSM particles. Therefore, the addition of LSM backbone may be ineffective, even negative in promoting the electrode performance, however, can significantly reduce the LSM infiltration threshold loading to form a percolating network. The trade-off between decreasing infiltration cycle and increasing TPB length demands an optimized content of LSM in backbone.