Boosting performance of the solid oxide fuel cell by facile nano-tailoring of La0.6Sr0.4CoO3-δ cathode

Sluggish kinetics for oxygen reduction reaction (ORR) is one of the greatest challenges limiting the electrochemical performance of solid oxide fuel cells (SOFCs). Surface modification through solution infiltration is recognized as a promising approach to boost the performance of the SOFCs. The conventional infiltration of electrocatalyst in porous scaffold results in discrete particles of active catalyst. However, in this study, we report a novel technique to produce the nano-tailored film of Sm_0.5Sr_0.5CO_3-δ (SSC) active catalyst on to La_0.6Sr_0.4CoO_3-δ (LSC) cathode of SOFC through controlling the drying rate during the infiltration process which resulted in a continous film like coating of SSC. The SOFC with LSC cathode containing SSC film-like nanostructure showed a two-fold performance increment and an excellent durability compared to the LSC cathode prepared through conventional methods. The higher performance of the film-like nanostructured LSC-SSC cathode is attributed to the remarkable reduction in the area-specific ohmic and polarization resistance due to the extension of cathode reaction sites and shorter diffusion lengths, thus, facilitating the ORR.     

Enhancing catalysis activity of La0.6Sr0.4Co0.8Fe0.2O3-δ cathode for solid oxide fuel cell by a facile and efficient impregnation process

The development of high performance electrocatalysts to promote oxygen reduction reaction (ORR) and to prolong the durability of cathodes of solid oxide fuel cell is essential at intermediate or low temperatures. Here, we report a facile and efficient spray impregnation strategy in enhancing catalytic activity of La_0.6Sr_0.4Co_0.8Fe_0.2O_3-δ (LSCF) due to the introduction of a multitude of homogeneous nanoparticles. With a highly active surface abundance in B-site cations, the modified LSCF cathode manifests an area-specific resistance (ASR) of ∼0.140 Ω cm², only a fifth of that for a pristine LSCF cathode (∼0.764 Ω cm²) at 600 °C, and anode-supported fuel cells with the decorated LSCF cathode show markedly improved peak power densities (∼0.94 W cm⁻² at 700 °C). Furthermore, the ORR kinetics of the modified LSCF cathode can be further enhanced by impregnating Ni(NO₃)₂·6H₂O and Co(NO₃)₂·6H₂O solution again. X-ray photoelectron spectroscopy analysis indicates that the homogeneous nanoparticles alter the distribution of Sr_surface and O_surface. It is found that ‘Co’ decoration can effectively alleviate the surface aggregation of Sr and ‘Co’ and ‘Ni’ decoration play a pivotal role in the reactivation of electrode surface.     

Preparation of Pr2NiO4+δ-La0.6Sr0.4CoO3-δ as a high-performance cathode material for SOFC by an impregnation method

As a Ruddlesden-Popper (RP) phase solid oxide fuel cell (SOFC) cathode material, Pr₂NiO_4+δ (PNO) is a critical challenge for SOFC commercialization due to the lack of oxygen vacancies and insufficient redox reaction (ORR) activity. In this paper, various concentrations of La_0.6Sr_0.4CoO_3-δ (LSC) nanoparticles are coated on the surface of PNO by an impregnation method, and the ORR kinetics of PNO is found to be improved by constructing a composite cathode with heterointerfaces. The formation of the heterointerface effectively enhances the transfer of interstitial oxygen in the PNO and the oxygen vacancies in LSC, which can promote the conduction of O^2? in the cathode and thus improves the ORR activity of the material. When the impregnation concentration of LSC reached C_LSC = 0.2 mol L^?1, the ORR activity can reach the highest level. At 700 °C, the area-specific resistance of PNO-LSC reaches 0.024 Ω cm², which is 83.4% lower than that of PNO (0.145 Ω cm²). And the peak power density of PNO-LSC reaches 0.618 W cm^?2, which is 1.89 times larger than that of PNO (0.327 W cm^?2). Therefore, the construction of composite cathodes with heterointerfaces via impregnation provides an alternative strategy for enhancing the ORR activity of the cathode materials in SOFC.     

A La0.8Sr0.2MnO3/La0.6Sr0.4Co0.2Fe0.8O3−δ core–shell structured cathode by a rapid sintering process for solid oxide fuel cells

A La_0.8Sr_0.2MnO₃ (LSM)/La_0.6Sr_0.4Co_0.2Fe_0.8O_3?δ (LSCF) core–shell structured composite cathode of solid oxide fuel cells (SOFCs) has been fabricated by wet infiltration followed by a rapid sintering (RS) process. The RS is carried out by placing LSCF infiltrated LSM electrodes directly into a preheated furnace at 800 °C for 10 min and cooling down very quickly. The heating and cooling step takes about 20 s, substantially shorter than 10 h in the case of conventional sintering (CS) process. The results indicate the formation of a continuous and almost non-porous LSCF thin film on the LSM scaffold, forming a LSCF/LSM core–shell structure. Such RS-formed infiltrated LSCF–LSM cathodes show an electrode polarization resistance of 2.1 Ω cm² at 700 °C, substantially smaller than 88.2 Ω cm² of pristine LSM electrode. The core–shell structured LSCF–LSM electrodes also show good operating stability at 700 °C and 600 °C over 24–40 h.     

Modified La0.6Sr0.4Co0.2Fe0.8O3-δ cathodes with the infiltration of Er0.4Bi1.6O3 for intermediate-temperature solid oxide fuel cells

Aiming to lower the activation energy and expedite the oxygen reduction reaction (ORR) process of La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF) cathodes for application in intermediate-temperature solid oxide fuel cells (IT-SOFCs), Er_0.4Bi_1.6O₃ (ESB) modified LSCF was prepared by infiltrating using organic solvents. The infiltration of ESB dramatically reduces the polarization resistances of LSCF cathodes (from 0.27 to 0.11 Ω cm² at 700 °C, from 0.58 to 0.25 Ω cm² at 650 °C), and lowers their activation energy (from 100.28 to 97.15 kJ mol^?1). Also, ESB makes the rate-limiting step of LSCF cathodes at high frequency change from the charge transfer process on the cathode to the adsorption and diffusion of oxygen on cathode surface. The single cell with ESB infiltrated LSCF cathodes shows a peak power density of 469 mW cm^?2 at 700 °C using humid hydrogen and air as fuels and oxidants, respectively, as well as a good short-term stability for 50 h.     

Effect of humidity on La0.4Sr0.6Co0.2Fe0.7Nb0.1O3−δ cathode of solid oxide fuel cells

Solid oxide fuel cells cathode often suffers from degradation caused by water vapor in air. Here, we report a cathode material, La_0.4Sr_0.6Co_0.2Fe_0.7Nb_0.1O_3−δ (LSCFN), and evaluate its humidity tolerance by the characterization of the materials in wet air with different water vapor concentration at different temperature. The X-ray diffraction analysis indicates that the crystal structure of LSCFN is relatively stable in wet air with no observable impurity. However, a crystalline contraction is observed. Exposure of wet air to LSCFN causes the decrease of electrical conductivity and increase of polarization resistance because H₂O might occupy the active sites for oxygen reduction reaction. For long-term operation, higher H₂O concentration in air accelerates the degradation of LSCFN cathode.     

SOFC cathode material of La1.2Sr0.8CoO4±δ with a fibrous morphology: Preparation and electrochemical performance

Using soluble salts as metal-ion sources and polyacrylonitrile (PAN) as a polymer matrix, La_1.2Sr_0.8CoO_4±δ cathode material with a fibrous morphology is prepared by electrostatic spinning, and microstructural characteristic of this material is investigated by field-emission scanning microscopy and X-ray diffraction. Electrochemical performance of the material in solid-oxide fuel cells is then tested. The results demonstrate that phase-pure La_1.2Sr_0.8CoO_4±δ fibrils with tetragonal structure can be prepared from fresh silky precursors using electrospinning after annealing at high temperature. Compared to the conventional cathode material that possesses a plain granular structure, La_1.2Sr_0.8CoO_4±δ fibrils exhibit superior electrochemical performance. At a temperature of 800 °C, the area specific resistance with this fibrous cathode is as low as 0.043 Ω cm², and maximum power density with the corresponding single-cell is 716 mW cm^?2, demonstrating the fast electrode kinetics in the O₂ reduction reaction. Comparatively, the area specific resistance with the plain cathode is 0.062 Ω cm², and the maximum power density with the corresponding single-cell is only 642 mW cm^?2. Under a constant voltage load of 0.6 V at a fixed temperature of 750 °C, the power output from a single-cell with the fiber-structured cathode maintains between 615 mW cm^?2 and 585 mW cm^?2 even after 15 h of running time, showing a slower fading rate and a more stable electrochemical performance than the plain cathode.     

Investigation of structural,electrical and electrochemical properties of La0.6Sr0.4Fe0.8Mn0.2O3-δ as an intermediate temperature solid oxide fuel cell cathode

La_0.6Sr_0.4Fe_0.8Mn_0.2O₃ (LSFM) compound is synthesized by sol-gel method and evaluated as a cathode material for the intermediate temperature solid oxide fuel cell (IT-SOFC). X-ray diffraction (XRD) indicates that the LSFM has a rhombohedral structure with R-3c space group symmetry. The XRD patterns reveal very small amount of impurity phase in the LSFM and Y₂O₃-stabilized ZrO₂ (YSZ) mixture powders sintered at 600, 700, 800 and 850 °C for a week. The maximum electrical conductivity of LSFM is about 35.35 S cm⁻¹ at 783 °C in the air. The oxygen chemical diffusion coefficients, D_Chem, are increased from 1.39 × 10⁻⁶ up to 1.44 × 10⁻⁵ cm² s⁻¹. Besides, the oxygen surface exchange coefficients, k_Chem, are obtained to lie between 2.9 × 10⁻³ and 1.86 × 10⁻² cm s⁻¹ in a temperature range of 600–800 °C. The area-specific resistances (ASRs) of the LSFM symmetrical cell are 7.53, 1.53, 1.13, 0.46 and 0.31 Ω cm² at 600, 650, 700, 750 and 800 °C respectively, and related activation energy, E_a, is about 1.23 eV.     

Effect of hetero-structured nano-particulate coating on the oxygen surface exchange properties of La0.6Sr0.4Co0.2Fe0.8O3-δ

In this study, dense La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF) electrodes decorated with the novel hetero-structured ceramic oxide mixture in four different ratios of Ce_0.8Gd_0.2O_2-δ (GDC) and La₂Mo₂O₉ (LMO). The time-dependent conductivity transients were acquire using electrical conductivity relaxation (ECR) technique at a chosen conditions of temperature in the range of 650–850 °C and instantaneous pO₂ step change between 0.2 and 0.8. Fitting of time-dependent conductivity to the appropriate non-equilibrium solutions of Fick's diffusion equation has yielded the chemical diffusion coefficient, D_chem, and oxygen surface exchange coefficient, k_chem. As expected, the D_chem of the coated samples remained invariant, whilst the k_chem is found to vary with the change in GDC-LMO coating mixture ratio. Substantial increase of a factor of 10 in the surface exchange coefficient is noticed for the LSCF coated with a 1:0.75 mixing ratio as compared to bare sample at 850 °C. The enhancement in k_chem is attributed to the optimal triple-phase boundary (TPB) regions which promotes oxygen surface exchange kinetics. Thus, coating of selective ratio of hetero-structured oxide in a form of nano-particulate layer over the LSCF surface is considered to be a promising candidate for solid oxide fuel cell (SOFC) cathode.     

La0.4Sr0.6Co0.7Fe0.2Nb0.1O3-δ perovskite prepared by the sol-gel method with superior performance as a bifunctional oxygen electrocatalyst

The advancement of efficient noble-metal-free electrocatalysts for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) is crucially important for energy storage devices such as fuel cells and metal-air batteries. This paper reports the development of a novel bifunctional perovskite, La_0.4Sr_0.6Co_0.7Fe_0.2Nb_0.1O_3-δ (LSCFN). The crystal structure, morphology, adsorption, valence, and oxygen catalytic activity of LSCFN were systematically studied. In addition, an investigation of the influence of the synthetic method on the oxygen catalytic activity was performed. Sol-gel and solid-phase methods were applied for the synthesis of LSCFN, and the resulting perovskites were denoted as LSCFN-SG and LSCFN-SP, respectively. The catalyst LSCFN-SG exhibited excellent bifunctional catalytic activity, with a low overpotential (360 mV) and superior stability in the OER. Subsequently, LSCFN-SG was used as the cathode catalyst in an aluminum-air battery and exhibited a high power density. The results of this study indicate that LSCFN-SG is a promising bifunctional oxygen electrocatalyst for metal-air batteries.     

Predicting elastic modulus of porous La0.6Sr0.4Co0.2Fe0.8O3-δ cathodes from microstructures via FEM and deep learning

In this work, a deep learning accelerated homogenization framework is developed for prediction of elastic modulus of porous materials directly from their inner microstructures. The finite element method (FEM) and the homogenization theory are used to obtain the macroscopic properties of materials based on their microstructures. Based on a large dataset consisting of various microstructures and corresponding elastic properties via FEM, a deep convolutional neural network (CNN) is trained to capture the nonlinear functional relationship between the microstructure features and their macroscopic elastic properties. The deep learning model is finally well validated against extra new samples with excellent predictive performances. This demonstrates that the CNN deep learning model can be trusted as a surrogate model for the FEM based homogenization method, with the computation time being reduced by several orders of magnitude. The proposed deep learning framework is highly extendable for prediction of various macroscopic properties from microstructures.     

In-situ strategy to suppress chromium poisoning on La0.6Sr0.4Co0.2Fe0.8O3-δ cathodes of solid oxide fuel cells

The surface segregation of strontium in the La_0.6Sr_0.4Co_0.8Fe_0.2O_3-δ (LSCF) electrode interacts with volatile contaminants such as chromium in the solid oxide fuel cell (SOFC) interconnect, causing deterioration in cell performance. A simple in-situ reaction strategy has been exploited to synergistically improve oxygen reduction reaction (ORR) activity in air and anti-chromium stability of LSCF electrode via infiltration and calcination of nickel nitrate and ferrite nitrate (NF) precursor on the LSCF backbone. The chemical compatibility, electrochemical performance, interfacial element distribution and stability in chromium-containing atmosphere of the as-prepared hybrid electrodes were systematically investigated. At a calcination temperature of 1100 °C, Sr(Co,Ni)O_3-δ layer was formed owing to Co diffusion and Sr precipitation from LSCF and the reaction with Ni atoms at the surface of LSCF. This will promote anti-chromium ability for the hybrid LSCF@NF cathode material. After the symmetrical cells were operated at 750 °C for 400 h under Cr contamination, the polarization resistance of LSCF@NF was only half of that of blank LSCF electrode with much less Cr species. This strategy via in-situ reaction may be extended to other high temperature energy conversion systems such as anti-sulfur and anti-carbon deposition of SOFC anodes and CO₂ resistance of cathodes.     

Enhancing the oxygen reduction activity of PrBaCo2O5+δ double perovskite cathode by tailoring the calcination temperatures

In this study, the oxygen reduction activity of PrBaCo₂O_5+δ (PBC) double perovskite is remarkably enhanced by rationally tuning the calcination temperatures of the cathode precursor for solid oxide fuel cells (SOFCs). Effects of the calcination temperatures on the phase structure, microstructure, surface area and oxygen reduction reaction (ORR) activity of PBC cathode is systematically investigated. The cathode with optimized calcination temperature (900 °C, PBC-900) shows excellent activity and stability for ORR at 600 °C in terms of area specific resistances (ASRs). A distinctive low ASR of 0.068 Ω cm² is obtained at 600 °C for PBC-900, which is 92.6%, 34.6% and 15.0% lower than PBC-800, PBC-1000 and PBC-1100, respectively. After operating for 250 h in air at 600 °C, the ASR value of PBC-900 is not significantly reduced. Furthermore, a single cell with PBC-900 cathode delivers attractive peak power density of 1.60 W cm⁻² at 600 °C. The present study suggests that the ORR activity of PBC cathode can be greatly boosted by rationally tailoring the calcination temperatures, which may bring new avenue for the design of highly active cathodes for SOFCs.     

Co-free La0.6Sr0.4Fe0.9Nb0.1O3-δ symmetric electrode for hydrogen and carbon monoxide solid oxide fuel cell

Co-free La_0.6Sr_0.4FeO_3-δ (LSFNb₀) and La_0.6Sr_0.4Fe_0.9Nb_0.1O_3-δ (LSFNb_0.1) perovskite oxides were prepared by a standard solid-state reaction method. The structural stability and electrochemical performance of La_0.6Sr_0.4Fe_0.9Nb_0.1O_3-δ as both cathode and anode were studied. Nb dopant in LSFNb₀ significantly enhances the structural and chemical stability in anode condition. At 800 °C, the polarization resistances (Rp) of LSFNb_0.1 symmetric electrode based on YSZ electrolyte are 0.5 and 0.05 Ω cm² in H₂ and air, respectively. The peak power densities of LSFNb_0.1 based on LSGM electrolyte-supported SSOFCs are 934 and 707 mW cm⁻² at 850 °C in H₂ (3% H₂O) and dry CO, respectively. Moreover, the symmetric cell exhibits reasonable stability in both H₂ and CO fuel, suggesting that La_0.6Sr_0.4Fe_0.9Nb_0.1O_3-δ may be a potential symmetric electrode material for hydrogen and carbon monoxide SOFCs.     

Investigation of La0.6Sr0.4Co1-xNixO3-δ (x=0, 0.2, 0.4, 0.6, 0.8) catalysts on solid oxide fuel cells anode for biogas dry reforming

The introduction of catalyst on anode of solid oxide fuel cell (SOFC) has been an effective way to alleviate the carbon deposition when utilizing biogas as the fuel. A series of La_0.6Sr_0.4Co_1-xNi_xO_3-δ (x = 0, 0.2, 0.4, 0.6, 0.8) oxides are synthesized by sol-gel method and used as catalysts precursors for biogas dry reforming. The phase structure of La_0.6Sr_0.4Co_1-xNi_xO_3-δ oxides before and after reduction are characterized by X-ray diffraction (XRD). The texture properties, carbon deposition, CH₄ and CO₂ conversion rate of La_0.6Sr_0.4Co_1-xNi_xO_3-δ catalysts are evaluated and compared. The peak power density of 739 mW cm^?2 is obtained by a commercial SOFC with La_0.6Sr_0.4Co_0.4Ni_0.6O_3-δ catalyst at 850 °C when using a mixture of CH₄: CO₂ = 2:1 as fuel. This shows a great improvement from the cell without catalyst for internal dry reforming, which is attributed to the formation of NiCo alloy active species after reduction in H₂ atmosphere. The results indicate the benefits of inhibiting the carbon deposition on Ni-based anode through introducing the La_0.6Sr_0.4Co_0.4Ni_0.6O_3-δ catalyst precursor. Additionally, the dry reforming technology will also help to convert part of the exhaust heat into chemical energy and improve the efficiency of SOFC system with biogas fuel.     

Enhancing oxygen reduction activity and CO2-tolerance of A-site-deficient BaCo0.7Fe0.3O3-δ cathode by surface-decoration with Pr6O11 particles

Sluggish oxygen reduction reaction (ORR) activity and poor CO₂-tolerance has been the long-standing limitations for the application of alkaline earth metal oxide cathode for solid oxide fuel cells (SOFCs). Here we report this situation can be ameliorated with a composite cathode based on Ba_0.9Co_0.7Fe_0.3O_3-δ (B90CF) by surface-decorated Pr₆O₁₁ (PO) particles. A halved polarization resistance is obtained by B90CF-15PO (PO of 15 wt%) cathode (0.033 Ω cm² at 700 °C) compared to blank B90CF, suggesting boosted oxygen reduction reaction activity owing to the accelerated oxygen surface exchange kinetics introduced by PO particles. PO protective layer also brings up desirable CO₂-tolerance for B90CF cathode due to the more stable fluorite cubic structure of PO and higher acidity of Pr³⁺/Pr⁴⁺ than Ba²⁺_, which ensures the stable operation of cells. This work demonstrates the positive potential of surface-decoration with PO in developing cathodes with high performance and CO₂-tolerance.     

Enhancement of an IT-SOFC cathode by introducing YSZ: Electrical and electrochemical properties of La0.6Ca0.4Fe0.8Ni0.2O3-δ-YSZ composites

La_0.6Ca_0.4Fe_0.8Ni_0.2O_3-δ (LCFN) is synthesized by liquid mixed method. Its crystalline structure is investigated by using X-ray diffraction. The results show that it has an orthorhombic perovskite structure with Pnma space group symmetry. The 8 mol % Y₂O₃-Stabilized ZrO₂ (YSZ) is physically mixed with various weight percentages of LCFN to form composite cathodes. High-temperature 4-probe conductivity measurements are performed to investigate the electrical behavior of the system. Electrochemical impedance spectroscopy is carried out using symmetric cells with YSZ substrates under equilibrium condition from 850 °C to room temperature. The electrical conductivity is reduced from 271.3 S cm⁻¹ to 49.5 S cm⁻¹ for LCFN and 10 wt % of YSZ-added LCFN (LCFN-YSZ-9010), respectively. The best area specific resistance among all fabricated composites is 0.0080(1) Ω.cm² at 850 °C for LCFN-YSZ-9010 which exhibits almost 50% lower value than LCFN. The YSZ-based composites appear to be suitable than the other low temperature electrolyte based composite cathodes.     

A highly scalable spray coating technique for electrode infiltration: Barium carbonate infiltrated La0.6Sr0.4Co0.2Fe0.8O3-δ perovskite structured electrocatalyst with demonstrated long term durability

This work demonstrated a highly scalable spray coating process for cathode infiltration with excellent long-term stability for the oxygen reduction reaction. Barium carbonate (BaCO₃) nanoparticles have previously demonstrated excellent catalytic activity for the oxygen reduction reaction and were chosen as a model system to be applied by spray coating onto La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF) and LSCF-SDC (Sm_0.2Ce_0.8O_2-δ) cathode materials. In this work, barium acetate solutions were modified by a surfactant to lower the surface tension and decrease the contact angle on LSCF which is a benefit for the infiltration process. In the LSCF electrode, BaCO₃ nano-particles exhibited significant interfacial contact with LSCF particles by the spray coating technique. As a result, the polarization resistance of BaCO₃ infiltrated LSCF was reduced from 2.5 to 1.2 Ωcm² at 700 °C. In addition, commercial full cell SOFCs with BaCO₃ infiltrated LSCF-SDC cathodes also demonstrated higher performance due to the reduced cathode resistance. At 750 °C, the electrode overpotential of the BaCO₃ infiltrated cell was much lower than that of baseline cell during long term testing (500 h). The polarization resistance of the BaCO₃ infiltrated LSCF-SDC electrode only increased by 1.6% after 500 h.     

Preparation and characterization of a redox-stable Pr0.4Sr0.6Fe0.875Mo0.125O3-δ material as a novel symmetrical electrode for solid oxide cell application

In this work, to simultaneously meet the requirements of good electrochemical performance and redox stability, perovskite oxide Pr_0.4Sr_0.6Fe_0.875Mo_0.125O_3-δ (PSFM) material has been developed as a novel redox-stable electrode for symmetrical cell application. The experimental results obtained by X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy show that metallic Fe nanoparticles will exsolve from the parent oxide PSFM through in-situ exsolution method when treating in 97% H₂–3% H₂O atmosphere, and then completely re-incorporate into the parent oxide in air, demonstrating excellent redox stability for PSFM material. In addition, the redox stability in electrochemical performance is also studied by recording the electrochemical impedance spectra and distribution of relaxation times (DRT) analysis. It is demonstrated that a constant electrode polarization resistance (R_p) of ~0.60 Ωcm² is achieved for the symmetrical cell with PSFM electrode in air at 800 °C after activation, and R_p value is significantly increased to 1.59 Ωcm² when exposing the symmetrical cell to 97% H₂–3% H₂O, which is possibly ascribed to the significantly decreased electrical conductivity form 71.0 Scm⁻¹in air to 3.8 Scm⁻¹ in 97% H₂–3% H₂O. Moreover, it is shown that R_p value recorded in air is effectively decreased to ~0.33 Ωcm², and keeps constant during the following 200-h redox stability testing, while R_p value measured in 97% H₂–3% H₂O atmosphere is gradually decreased to 0.82 Ωcm², which can be explained by the enhanced electro-catalytic properties of PSFM electrode induced by the gradually exsolved Fe nanocatalysts from parent PSFM electrode. At the same time, DRT analysis demonstrates that the sub-electrode process including oxygen/hydrogen adsorption, dissociation ionization and surface diffusion to triple phase boundaries occurred at the electrode/electrolyte interfacial is the predominant rate-limiting step, which can be effectively accelerated by surface modification and exsolved Fe nanoparticles. These results indicate that PSFM is a promising symmetrical electrode material for symmetrical cell application because of its good electrochemical performance and excellent long-term redox stability.     

Validating the efficiency of γ-Al2O3/La0.6Sr0.4Co0.2Fe0.8O3-δ double-layer electrolyte for low temperature solid oxide fuel cell

Perovskite La_0.6Sr_0.4Co_0.2Fe_0.8O_3+δ (LSCF) as a promising cathode material possessed overwhelming electronic conduction along with certain ionic conductivity. Its strong electron conduction capability hinder the application of pure-phase LSCF as electrolyte in semiconductor membrane fuel cell (SMFC). In order to constrain the electron transport and take advantage of the decent ion conduction of LSCF, a thin layer of γ-Al₂O₃ with insulating property was added as an electron barrier layer and combine with LSCF to form a two-layer structure electrolyte. Through adjusting the weight ratio of LSCF/γ-Al₂O₃ to optimize the thickness of double layers, an open circuit voltage of 0.98 V and a maximum power density of 690 mW/cm² was received at 550 °C. At the same time, SEM, EIS and other characterization technology had proven that the LSCF/γ-Al₂O₃ bi-layer electrolyte can work efficiently at low temperature. The advantage of this work is the application of double-layer (γ-Al₂O₃/LSCF) structure electrolyte to instead of mixed material electrolyte in low-temperature solid oxide fuel cells. Structural innovation and the using of insulating materials provided clues for the further development of SMFC.