Study on durability of novel core-shell-structured La0.8Sr0.2Co0.2Fe0.8O3-δ@Gd0.2Ce0.8O1.9 composite materials for solid oxide fuel cell cathodes

Core-shell-structured La_0.8Sr_0.2Co_0.2Fe_0.8O_3-δ@Gd_0.2Ce_0.8O_1.9 (LSCF@GDC) composite materials are synthesized and sintered as the SOFC cathodes by screen-printing method. The durability of core-shell-structured LSCF@GDC composite cathodes are evaluated through constant current polarizations (CCP) process at 750 °C and the results indicate that the core-shell-structured LSCF@GDC composite cathode (nanorod, 0.6) possesses an excellent long-term stability. In addition, molecular dynamics (MD) model is developed and applied to simulate the interaction between LSCF and GDC particles. According to the simulation results, compressive stress is generated at the cathode-electrolyte interface by the coated GDC layer. Combining with the X-ray diffraction (XRD) refinement results, it's revealed that the lattice strains are introduced in LSCF lattices because of the compressive stress. Furthermore, XPS results show that the core-shell-structured LSCF@GDC composite cathode (nanorod, 0.6) possess a better inhibition ability for Sr surface segregation. This study provides a possible way to suppress Sr surface segregation.     

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.     

Effects of PdO modification on the performance of La0.6Sr0.4Co0.2Fe0.8O3−δ cathodes for solid oxide fuel cells: A first principle study

Effects of palladium (Pd) impregnation on the performance of La_0.6Sr_0.4Co_0.2Fe_0.8O_3?δ (LSCF) cathodes are investigated with density functional theory plus U (DFT + U) and experimental methods. In-situ high temperature X-ray diffractometer results show that the impregnated Pd species exist at states of palladium oxide (PdO) at 700 °C. The measured electrochemical impedance spectroscopy at 700 °C indicates PdO modification promotes the catalytic activity of LSCF cathodes. The modification structure of PdO on LSCF surfaces and effects of PdO modification on the performance of LSCF cathodes are investigated with DFT + U methods. The results show that B-8 with PdO molecule modification by a parallel posture on LSCF surface is the most stable structure. O₂ prefers to be adsorbed on AO-terminated surfaces rather than that on BO₂-terminated ones. The oxygen surface adsorption activity of LSCF surface is improved by PdO modification. The calculated partial densities of states (PDOS) and Fermi level of O₂ adsorption on LSCF surfaces imply that the charge transfer is easier with PdO modification than that without PdO modification because PdO acts as a metal-like modification. The PdO modification on LSCF surface leads to a better oxygen surface adsorption activity of LSCF cathodes.     

Nanocomposite BaZr0.7Sm0.1Y0.2O3−δ–La0.8Sr0.2Co0.2Fe0.8O3−δ materials for single layer fuel cell

Single layer fuel cell (SLFC) is a novel breakthrough in energy conversion technology. This study is to realize the physical-electrochemical co-driving mechanism of a single component device composed of mixed ionic and semiconductor material. This paper is focused on investigating the mechanism and characterization of synthesized nanocomposite BaZr_0.7Sm_0.1Y_0.2O_3?δ (BZSY)–La_0.8Sr_0.2Co_0.2Fe_0.8O_3?δ (LSCF) in proportion 1:1 and 3:7 for SLFC. The crystallographic structure and morphology is studied with X-ray diffraction (XRD) and scanning electron microscopy (SEM). The nano-particles lie in the range of 100–210 nm. Ultraviolet (UV) and electrochemical impedance spectroscopy (EIS) is used to analyze the semiconducting nature of nanocomposite (BZSY–LSCF). The performance of SLFC was carried out at different temperatures ranging between 400 and 650 °C. The mixed conductivity of the synthesized material was about 2.3 S cm^?1. The synergic effect of junction and energy band gap towards charge separation as well as the promotion of ion transport by junction built in field contributes to the working principle and high power output in the SLFC.     

Improved stability of nano-sized La0.6Sr0.4Co0.2Fe0.8O3-δ-Ce0.8Sm0.2O1.9 composite cathodes by substituting Sr2+ with Ca2+

The nano-sized composite cathodes prepared by infiltrating La_0.6Sr_{0. 4}Co_0.2Fe_0.8O_3-δ (LSCF) or La_0.6Ca_0.4Co_0.2Fe_0.8O_3-δ (LCCF) into the Ce_0.8Sm_0.2O_1.9 (SDC) scaffolds exhibit different electro-catalytic activity and microstructure evolution. Compared with LSCF-SDC nano-sized composite cathode, the LCCF-SDC composite cathode shows the higher microstructure stability. There is no observable coarsening or sintering and no diffraction peaks of other impurity phase are detected for both LSCF and LCCF after being aged at 600 °C for 500 h, but the lattice distortion is less if La³⁺ ions are substituted by Ca²⁺ ions instead of by Sr²⁺ in LaCo_0.2Fe_0.8O_3-δ (LCFO) lattice. The oxygen vacancy concentration is also less in LCCF than in LSCF. The less lattice distortion and oxygen vacancy concentration prohibit the Ca²⁺ ions segregation on the LCCF cathode surface because of less strain in the LCCF lattice and less electrostatic interactions between the negatively charge A-site dopants (Ca′_La) and the positively charged oxygen vacancies (V_o^··) on LCCF surface. The greater binding energy of Ca–O maybe also hinder the enrichment of Ca²⁺ ions on the cathode surface. After being aged in air at 600 °C for 500 h, more Sr²⁺ ions gather on the LSCF cathode surface to form a Sr-rich inert phase, which is detrimental to the oxygen reduction reaction on the cathode surface.     

Influence of polarization on the electrochemical activity of La2–xCaxNiO4+δ electrodes in contact with Ce0.8Sm0.2O1.9 electrolyte

The effect of electrode polarization on the electrochemical activity of La₂NiO_4+δ and La_1.9Ca_0.1NiO_4+δ electrodes in contact with the Ce_0.8Sm_0.2O_1.9 electrolyte is studied by impedance spectroscopy. It is found that anodic polarization facilitates electrode reaction for both electrodes leading to significant decrease in the polarization resistance. The effect of cathodic polarization differs between the electrodes: the polarization resistance of La₂NiO_4+δ electrode slightly increases, while the polarization resistance of La_1.9Ca_0.1NiO_4+δ electrode strongly decreases with the increase in the applied potential. It is established that in all cases the polarization mostly affects the low-frequency stage of the electrode reaction, connected with oxygen surface exchange and diffusion. The surface state of the samples after exposure under polarization is studied by X-ray photoelectron spectroscopy. Correlations between electrochemical activity of the electrodes and the changes in their surface composition under polarization are discussed.     

Effects of humidity on Ba0.9Co0.7Fe0.2Nb0.1O3−δ cathode performance and durability of Solid Oxide Fuel Cells

Solid Oxide Fuel Cells (SOFCs) cathode often suffers from degradation resulting from different contaminations, such as water vapor from air, when operated under the realistic environments. In this work, we demonstrate an excellent water vapor tolerant Ba_0.9Co_0.7Fe_0.2Nb_0.1O_3?δ (BCFN) cathode for SOFCs. The concentration effects of humidity on BCFN cathode performance including oxygen reduction reaction (ORR) kinetics and durability have been studied. The X-ray diffraction measurement indicates that humidity has no observable effects on BCFN materials. The electrochemical performance change in BCFN cathode seems to be more sensitive to the humidity at a lower temperature such as 650 °C than that at 800 °C. A low polarization resistance of 0.069 Ω cm² at 650 °C is obtained in 3% water vapor, and then the polarization resistance increases with increase of water vapor content. Furthermore, the electrochemical impedance spectra indicate that BCFN cathode contaminated by higher humidity can be recovered by purging air again.     

Kinetics of oxygen reaction in porous La0.6Sr0.4Co0.2Fe0.8O3–δ-Ce0.8Gd0.2O1.9 composite electrodes for solid oxide cells

Kinetics of oxygen reaction in porous La_0.6Sr_0.4Co_0.2Fe_0.8O_3–δ (LSCF) and La_0.6Sr_0.4Co_0.2Fe_0.8O_3–δ-Ce_0.8Gd_0.2O_1.9 (LSCF-GDC) electrodes are systematically studied. Normally, there are two pathways of oxygen reaction in porous LSCF: in reaction region with oxygen exchanging at electrode/air interface, and around electrode/electrolyte interface with oxygen exchanging at electrode/electrolyte/air triple-phase boundary (TPB). GDC in porous LSCF-GDC accelerates oxygen transport and oxygen gas diffusion during oxygen reaction. In addition, because the formation of LSCF/GDC interface increases the length of TPB and affects the geometry of reaction region, oxygen reaction in LSCF-GDC tends to proceed in the TPB pathway. The performance and oxygen reactions of LSCF-GDC are evaluated at 650 °C and 850 °C. Oxygen reaction in LSCF-GDC is suppressed by CO₂, but increasing GDC content is able to improve the CO₂ tolerance of electrode. Though the performance reduction by H₂O is unobvious, H₂O can aggravate CO₂ degradation at low temperature.     

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.     

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.     

High-performance anode-supported solid oxide fuel cells with co-fired Sm0.2Ce0.8O2-δ/La0.8Sr0.2Ga0.8Mg0.2O3−δ/Sm0.2Ce0.8O2-δ sandwiched electrolyte

In this study, intermediate-temperature solid oxide fuel cells (IT-SOFCs) with a nine-layer structure are constructed via a simple method based on the cost-effective tape casting-screen printing-co-firing process with the structure composed of a NiO-based four-layer anode, a Sm_0.2Ce_0·8O_2-δ(SDC)/La_0·8Sr_0.2Ga_0.8Mg_0·2O_3?δ (LSGM)/SDC tri-layer electrolyte, and an La_0·6Sr_0·4Co_0·2Fe_0·8O_3-δ (LSCF)-based bi-layer cathode. The resultant SDC (4.14 μm)/LSGM (1.47 μm)/SDC (4.14 μm) tri-layer electrolyte exhibits good continuity and a highly dense structure. The R_o and R_p values of the single cell are observed to be 0.15 and 0.08 Ω cm² at 800 °C, respectively, and the MPD of the cell is 1.08 Wcm-2. The high MPD of the cell appears to be associate with the significantly lower area-specific resistance and the reasonably high OCV. Compared to those with a similar electrolyte thickness reported in prior studies, the nine-layer anode-supported IT-SOFC with a tri-layer electrolyte developed by the study demonstrates superior cell properties.     

Role of mixed conducting Pr0.1Gd0.1Ce0.8O1.9-δ barrier layer on the promotion of SOFC performance

The cathode activity in a solid oxide fuel cell can be promoted by introducing various catalysts to reduce its polarization resistance towards oxygen reduction, and thus improve cell performance. In this work, the La_0.6Sr_0.4Co_0.2Fe_0.8O₃ (LSCF) cathode surface is modified by the infiltration of Pr₆O₁₁ and the power density at 0.8 V and 750 °C is improved by 21%. Moreover, by replacing the traditional barrier layer Gd_0.2Ce_0.8O_1.9 with mixed conducting Pr_0.1Gd_0.1Ce_0.8O_1.9 (PGCO), the power density increases by 38%. The ohmic resistance is dramatically reduced by applying the PGCO interlayer. The distribution of relaxation time was used to analyze the mechanism for which the polarization resistance was decreased, attributing to the mixed conduction nature in PrO_x. An increase of power density, ～0.358 W/cm² (71%) at 0.8 V, is achieved with the implementation of both surface modification and buffer layer engineering.     

Electrochemical and thermal properties of SmBa0.5Sr0.5Co2O5+δ cathode impregnated with Ce0.8Sm0.2O1.9 nanoparticles for intermediate-temperature solid oxide fuel cells

SmBa_0.5Sr_0.5Co₂O_5+δ (SBSC55) impregnated with nano-sized Ce_0.8Sm_0.2O_1.9 (SDC) powder has been investigated as a candidate cathode for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The cathode chemical compatibility with electrolyte, thermal expansion behavior, and electrochemical performance are investigated. For compatibility, a good chemical compatibility between SBSC55 and SDC electrolyte is still kept at 1100 °C in air. For thermal dilation curve, it could be divided into two regions, one is the low temperature region (100–265 °C); the other is the high temperature region (265–850 °C). In the low temperature region (100–265 °C), a TEC value is about 17.0 × 10^?6 K^?1 and an increase in slope in the higher temperatures region (265–800 °C), in which a TEC value is around 21.1 × 10^?6 K^?1. There is an inflection region ranged from 225 to 330 °C in the curve of d(δL/L)/dT vs. temperature. The peak inflection point located about 265 °C is associated to the initial temperature for the loss of lattice oxygen and the formation of oxygen vacancies. For electrochemical properties, the polarization resistances (R_p) significantly reduced from 4.17 Ω cm² of pure SBSC55 to 1.28 Ω cm² of 0.65 mg cm^?2 of SDC-impregnated SBSC55 at 600 °C. The single cell performance of SBSC55∣SDC∣Ni-SDC loaded with 0.65 mg cm^?2 SDC exhibited the optimum power density of 823 mW cm^?2 at operating temperature of 800 °C. Based on above-mentioned properties, SBSC55 impregnated with an appropriate SDC is a potential cathode for IT-SOFCs.     

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.     

Synthesis and electrochemical characterization of La0.6Sr0.4Co0.2Fe0.8O3–δ / Ce0.9Gd0.1O1.95 co-electrospun nanofiber cathodes for intermediate-temperature solid oxide fuel cells

Synthesis and electrochemical characterization of composite cathodes, formed from a mixture of La_0.6Sr_0.4Co_0.2Fe_0.8O_3–δ (LSCF) and Ce_0.9Gd_0.1O_1.95 (GDC) nanofibers, is reported. The electrodes are obtained by simultaneous electrospinning of the two precursor solutions, using apparatus equipped with two spinnerets working in parallel. Results of electrochemical testing carried out through electrochemical impedance spectroscopy (EIS) are presented and discussed. The results suggest that the electrochemical reaction takes place in an electrode region close to the electrode/current collector interface and that the oxygen ions then flow along the ionic conducting path of the GDC fibers. At 650 °C, the polarization resistance is R_p = 5.6 Ω cm^?2, in line with literature values reported for other IT-SOFC cathodes.     

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.     

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.     

La0.8Sr0.2Mn0.8Co0.2O3-δ perovskite as an efficient functional electrocatalyst for oxygen reduction reactions

The negative effects of the widespread and rough use of fossil energy have promoted the emergence of new energy technologies. Cost-effective electrocatalysts play an irreplaceable role in energy conversion and storage, especially oxygen reduction reactions (ORR) catalysts. While the reserves of precious metal catalysts are rare and expensive, it is of prime importance to develop catalysts that can replace precious metals. In the present work, La_0.8Sr_0.2Mn_0.8Co_0.2O_3-δ (LSMC) with Mn and Co is successfully prepared by sol-gel method and subsequent calcination. The characterizations of physical phase, microstructure, BET and valence state of elements demonstrate that LSMC material possesses ample mesoporous structure, large specific surface area, and multivalent elements, which can provide abundant active sites for ORR. The electrochemical tests reveal that the LSMC delivers outstandingly higher electrocatalytic activity for ORR, relatively lower overpotential and Tafel slope and a better long-term stability than the other perovskites (LSM, LSC) under alkaline condition. Furthermore, the coupling effects of high content of high-valence Co, multivalent Mn and large amounts of adsorbed oxygen endow the catalyst excellent ORR electrocatalytic activity. The present work investigating the effect of Mn and Co elements on the electrocatalysis of LSMC perovskite, will provide the possibility of developing a new type of perovskite electrocatalyst with excellent ORR electrocatalytic activity and low cost.     

Electrochemical performance of La0.65Sr0.35MnO3 oxygen electrode with alternately infiltrated Sm0.5Sr0.5CoO3-δ and Sm0.2Ce0.8O1.9 nanoparticles for reversible solid oxide cells

La_1-xSr_xMnO₃ is a well-known oxygen electrode for reversible solid oxide cells (RSOCs). However, its poor ionic conductivity limits its performance in redox reaction. In this study, we selected Sm_0.5Sr_0.5CoO_3-δ (SSC) as catalyst and Sm_0.2Ce_0.8O_1.9 (SDC) as ionic conductor and sintering inhibitor to co-modify the La_0.65Sr_0.35MnO₃ (LSM) oxygen electrode through an alternate infiltration method. The infiltration sequence of SSC and SDC showed an influence on the morphology and performance of LSM oxygen electrode, and the influence was gradually weakened with the increasing infiltration time. The polarization resistance of the alternately infiltrated LSM-SSC/SDC electrode was 0.08 Ω cm² at 800 °C in air, which was 3.36% of the LSM electrode (2.38 Ω cm²). The Ni-YSZ/YSZ/LSM-SSC/SDC single cell attained a maximum power density of 1205 mW cm^?2 in SOFC mode at 800 °C, which was 8.73 times more than the cell with LSM electrode. The current density achieved 1620 mA .cm^?2 under 1.5 V at 800 °C in SOEC mode and the H₂ generation rate was 3.47 times of the LSM oxygen electrode.     

A promising Bi-doped La0.8Sr0.2Ni0.2Fe0.8O3-δ oxygen electrode for reversible solid oxide cells

Reversible solid oxide cells (RSOCs) are clean and effective electrochemical conversion devices that require highly active electrodes and stable electrochemical performance for the practical application. Herein, we investigate a series of La_0.8-xBi_xSr_0.2Ni_0.2Fe_0.8O_3-δ (LBSNF-x, x = 0.0, 0.05, 0.1, 0.15) oxides as the potential oxygen electrode material for RSOCs. The properties of electrical conductivity, thermal expansion coefficient, and chemical compatibility with the Ce_0.9Gd_0.1O_1.95 (GDC) barrier layer of LBSNF-x oxides are evaluated. When LBSNF-0.1 and GDC forms a composite oxygen electrode with the ratio of 7:3, it shows the lowest polarization resistance with fastest oxygen reduction reaction activity in the symmetrical cell test. Then the cell with the configuration of Ni-YSZ/YSZ/GDC/LBSNF-0.1-GDC was prepared and evaluated both in fuel cell (FC) and electrolysis cell (EC) mode. The maximum power density of 824 mW cm⁻² is obtained at 800 °C in FC mode, and current density of 1.20 A cm⁻² is achieved under 50% steam content at 1.3 V in EC mode. Additionally, the cell exhibits good stability both in FC and EC mode after 80 h test at 700 °C. The results of this work provide a strong support for application of the LBSNF-0.1-GDC oxygen electrode for reversible solid oxide cells.