LSCF Surface Research Articles

Cobalt oxide enhanced lanthanum strontium cobalt ferrite electrode for solid oxide fuel cells

A Co3O4 enhanced La0.8Sr0.2Co0.5Fe0.5O3 - δ (LSCF) electrode is developed for use in air electrodes with proton conducting solid oxide fuel cell (SOFC). The incipient wetness impregnation method enables Co3O4 nanoparticles on the LSCF surface without altering the bulk porosity of the LSCF electrode. The polarization resistance of LSCF electrodes is significantly reduced by Co3O4 doping, and both charge transfer and diffusion/conversion resistances were positively affected. The highest reduction in charge transfer resistance is obtained at 700 °C, which is increased from 21 % to 32 % through reduction of po2. Conversely, the highest reduction in diffusion/conversion resistance is achieved at 550 °C. By increasing po2, the reduction is increased from 57 % to 66 % and its activation energy is reduced up to 33 % compared to pure LSCF. The lowest total area specific resistances obtained under air are 1.45 Ω·cm2, 2.95 Ω·cm2, 6.75 Ω·cm2 and 16.45 Ω·cm2 at 700 °C, 650 °C, 600 °C and 550 °C, respectively.

Catalyst-modified perovskite hollow fiber membrane for oxidative coupling of methane

The catalytic oxidative coupling of methane (OCM) to C2 hydrocarbons (C2H6 and C2H4) represents one of the most effective ways to convert natural gas to more useful products, which can be performed effectively using La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) perovskite hollow fiber membrane microreactor. In this work, the effects of adding a thin BaCe0.8Gd0.2O3−δ (BCG) catalyst film onto the inner LSCF fiber surface as the OCM catalyst and a porous Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) perovskite layer onto the outer LSCF surface to improve the oxygen permeation were evaluated. Between 700 °C and 1000 °C, methane conversion increased in the order of uncoated, BCG and BSCF-coated, and BCG-coated LSCF hollow fiber while C2-selectivity and C2-yield increased in the order of BCG and BSCF-coated, uncoated, and BCG-coated LSCF hollow fiber. Oxygen permeation flux at the same temperature range, on the other hand, was enhanced in the order of uncoated, BCG-coated, and BCG and BSCF-coated LSCF hollow fiber. This finding demonstrates the complex interplay between oxygen permeation and OCM performance. The BCG and BSCF-coated hollow fiber was also subjected to thermal cycles between 850 °C and 900 °C for up to 175 hours during which the fiber showed minor degradation in oxygen permeation fluxes and relatively stable OCM performance.

Gold particle effect on high temperature oxygen reduction reaction via lanthanum strontium cobaltite ferrite electrocatalyst

Gold is generally considered to be inert for electrochemical reactions in solid oxide fuel cells (SOFCs). It is thus used as the standard current collector to characterize the catalytic activity of various cathode materials including the state-of-the-art lanthanum strontium cobalt iron oxide (LSCF). This work shows that gold is not inert but active for oxygen reduction reaction (ORR) via LSCF. Electrical conductivity relaxation measurement shows that scattered gold particles on LSCF surface can greatly increase the ORR rate. Gold improves the chemical oxygen surface exchange coefficient by a factor up to 27.5. The improvement is much high at reduced temperature from 800 to 650 °C. In addition, gold particles with smaller size show better performance in enhancing the ORR activity.

Physical characterization of LSCF-CuO via enhanced modified sol–gel method for intermediate temperature Solid oxide Fuel Cells (IT-SOFCs)

Enhanced modified sol–gel with addition of EDTA as chelating agent was used to produce composite cathode LSCF-CuO for Intermediate Temperature Solid Oxide Fuel Cells (IT-SOFC). Physical properties of La0.6Sr0.4Co0.2Fe0.8-CuO (LSCF-CuO) composite cathode prepared using modified sol–gel method was compared with conventional Pechini method from previous study. LSCF-CuO was calcined at varied range of temperature from 600 °C to 900 °C. TGA results showed LSCF achieved complete perovskite formation after calcined above 600 °C and DTA showed formation of lattice oxygen happened at 570 °C. Although weight loss curve flattened after 600 °C, there were still small weight loss occurred until 800 °C where there is completely no weight loss recorded after that temperature suggesting that LSCF-CuO completely formed after this temperature. Meanwhile, XRD analysis showed no shifted peak with high purity of LSCF-CuO were achieved after calcined at 800 °C with nano size crystal of 40.67 nm based from Scherrer equation. SEM and BET showed similar analysis pattern where particle size increase as the calcining temperature increases. Key mapping data from EDX analysis shows a good scatter of CuO across the cathode surface indicating a good distribution of CuO across LSCF surface where the infiltration on B-Site of cathode was succeed.

Combined Cr and S poisoning behaviors of La1−xSrxMnO3±δ and La1−xSrxCo1−yFeyO3−δ cathodes in solid oxide fuel cells

Although the individual effects of airborne Cr and S contaminants on SOFC cathode performance degradation have been extensively studied, the combined effects of Cr and S contaminants remain largely unexplored. Under the real SOFC operating condition where the Cr and S species coexist, their effects may compete, affecting the poisoning behavior. Our investigation reveals that the combined Cr and S poisoning behavior of LSCF remains different from those of individual Cr and S poisonings, while the combined poisoning mechanism of LSM is equivalent to the sum of those of individual Cr and S effects. For LSCF electrode, gaseous Cr species are deposited mainly at the LSCF/GDC interface by electrochemical reduction, rather than forming SrCrO4 on LSCF surfaces (as in the case of Cr-only poisoning), indicating no reaction between Cr vapors and SrO on the LSCF surface. Thermodynamic analysis demonstrates that the SrO on LSCF surface absorbs SO2 (g) and thereby loses the Cr-gettering effect, allowing Cr vapors to flow through LSCF and to reach the LSCF/GDC interface where the Cr deposition occurs. Unlike LSCF, LSM electrode shows cumulative effects of Cr and S, as Cr accumulation occurs at the triple-phase boundary and S absorption takes place at localized Sr-rich regions.

A detailed kinetic model for the reduction of oxygen on LSCF-GDC composite cathodes

A kinetic investigation of the Oxygen Reduction Reaction (ORR) is performed on LSCF-GDC composite cathodes (La0.4Sr0.6Co0.2Fe0.8O3-δ/Ce0.9Gd0.1O2-δ 50/50) spanning a wide range of operating conditions. EIS tests are carried out on symmetric cells between 700 °C and 560 °C at OCV, with O2/N2 mixtures at varying O2 molar fraction (5–21%). A dynamic, one-dimensional, physic model of the LSCF-GDC electrode is applied to rationalize the experimental results. The model simulates the spectra by solving mass and charge conservation equations, including terms for gas diffusion in the porous electrode and solid state transport in both the LSCF and the GDC lattice. A thermodynamically consistent, detailed kinetic scheme is applied to describe the ORR mechanism, which takes into account elementary steps of adsorption and desorption, first and second electronation at the gas/electrode interface, interfacial and lattice ion transfer. A full set of rate parameters (pre-exponential factors and activation energies) is derived by fitting to inhouse-measured impedance data, and validated against a well-established literature dataset. The sensitivity analysis supports the prevailing role of the TPB route over the 2PB route, and highlights that the transfer of a single-charged oxygen adatom from the LSCF surface to the GDC lattice governs the ORR. The model clarifies the origin of distortions in measured impedance arcs, and captures the effect of O2 pressure on the observed electrochemical activity.

Magnesium oxide as synergistic catalyst for oxygen reduction reaction on strontium doped lanthanum cobalt ferrite

MgO has been demonstrated to have positive effects on the oxygen reduction reaction (ORR) at the strontium doped lanthanum cobalt ferrite (LSCF) cathode for solid oxide fuel cells. MgO particles, which were prepared by the infiltration technique using magnesium nitrate as the precursor, are compatible with LSCF under the experimental conditions for electrode fabrication. Electrical conductivity relaxation investigation demonstrated that the chemical oxygen surface exchange coefficient at 750 °C can be improved by a factor up to 2.4 through coating LSCF surface with MgO particles. Electrochemical impedance analysis showed that the area specific interfacial polarization resistance can be obviously reduced, such as from 0.49 Ω cm2 to 0.31 Ω cm2 at 650 °C when a porous LSCF electrode supported on samaria-doped ceria electrolyte was infiltrated with 1.01 wt% MgO particles. Distribution of relaxation time (DRT) analysis suggested that the resistance reduction is associated with the charge transfer process. Thus, MgO can enhance ORR on LSCF electrocatalyst, like the previously reported alkaline earth metal compounds of BaCO3, SrCO3 and CaO.

A Multiscale Model for Electrochemical Reactions in LSCF Based Solid Oxide Cells

Lanthanum Strontium Cobalt Ferrite (La1 − xSrxCo1 − yFeyO3 − δ or LSCF), a mixed ionic-electronic conductor is widely used as an electrode in solid oxide cells (SOCs). The reactions and transport at this oxygen electrode are complex and distributed across several length and time scales. However, a comprehensive computational model that could provide accurate and reliable linkages between different scales to predict the electrochemical characteristics of these electrodes is missing. Here, we develop a multiscale model combining density functional theory calculations, transition state theory and continuum modeling for the oxygen-based reactions at the cathode/anode in LSCF based solid oxide fuel cells (SOFC)/electrolysis cells (SOEC), to elucidate the critical reaction steps and predict the performance of the device. Density functional theory calculations were used to obtain the free energy barriers for different reaction steps while transition state theory was used to predict the reaction rate constants/diffusivities for each step based on the free energy barriers. The continuum theory utilized these reaction rate constants and diffusivities to obtain the overpotential-current density relations. The proposed multiscale model yields a quantitative agreement with the overpotential-current density data from experiments. The results indicate that oxygen exchange at the LSCF surface, rather than the triple-phase boundary, is the main contributing reaction pathway for a single phase LSCF electrode. For the entire cathodic and anodic reaction pathway, the reaction step involving the splitting of the surface peroxo units into oxo units under SOFC mode or the combination of surface oxo units into peroxo units under SOEC mode is the rate-limiting reaction step, and the diffusion of oxide ions in bulk LSCF is the rate-limiting diffusion step. We also predict that the SrO terminated LSCF surface is not an efficient surface structure for oxide ion diffusion.

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 La0.6Sr0.4Co0.2Fe0.8O3−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.

Evaluation of La0.6Sr0.4Co0.2Fe0.8O3-Gd0.1Ce0.9O1.95 composite cathode with three dimensional microstructure reconstruction

Abstract In the present study, the polarization characteristics of La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3 (LSCF) - Gd 0.1 Ce 0.9 O 1.95 (GDC) composite cathodes with different volume ratios were investigated. Samples with volume ratios of 20:80, 30:70, 50:50, 70:30 and 100:0 vol % were tested. The electrochemical impedance spectroscopy tests and current voltage curve measurements were carried out for the current densities from 0 to 0.2 Acm −2 with an interval of 0.05 Acm −2 . The results showed that a volume ratio of LSCF:GDC = 30:70 composite cathode led to the lowest overpotential, and the overpotential increased in the order of 30:70, 50:50, 70:30, 100:0, 20:80 vol %. Three dimensional microstructures of composite cathodes were reconstructed and quantified by dual beam focused ion beam-scanning electron microscope (FIB-SEM). The results showed that neither LSCF surface area nor triple phase boundary (TPB) alone could explain the dependence of polarization characteristics on volume ratios. Current and electrochemical potential distributions were simulated by the Lattice Boltzmann method, in which both surface and TPB reactions were considered. Prediction considering both surface and TPB reactions could predict qualitatively the dependence of overpotentials on LSCF - GDC cathode composition.

Plasma Glow Discharge as a Tool for Surface Modification of Catalytic Solid Oxides: A Case Study of La0.6Sr0.4Co0.2Fe0.8O3−δ Perovskite

Performance of solid oxide fuel cells (SOFCs) is hindered by the sluggish catalytic kinetics on the surfaces of cathode materials. It has recently been reported that improved electrochemical activity of perovskite oxides can be obtained with the cations or the oxides of some metallic elements at the surface. Here, we used a cost-effective plasma glow charge method as a generic tool to deposit nano-size metallic particles onto the surface of SOFC materials. Ni nano-scale patterns were successfully coated on the La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) surface. The microstructure could be well controlled. The kinetics of oxygen exchange on the modified LSCF surface was promoted significantly, confirmed by electrical conductivity relaxation (ECR) measurement.

Copper oxide as a synergistic catalyst for the oxygen reduction reaction on La0.6Sr0.4Co0.2Fe0.8O3−δ perovskite structured electrocatalyst

Abstract This work presents the effect of dispersed copper oxide (CuO) nanoparticles on the oxygen reduction reaction (ORR) on a typical solid oxide fuel cell (SOFC) electrocatalyst, La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF). The ORR kinetics were enhanced by a factor up to 4 at 750 °C as demonstrated by electrical conductivity relaxation measurements used to determine the chemical surface exchange coefficient, kchem. The value of kchem increased from 2.6 × 10−5 cm s−1 to 9.3 × 10−5 cm s−1 at 750 °C when the LSCF surface was coated with submicron CuO particles. The enhanced kchem was attributed to additional reactions that occur on the CuO surface and at the LSCF-CuO-gas three-phase boundaries (3PBs) as suggested by the kchem dependence on CuO coverage and 3PB length. This enhancement was further demonstrated by the introduction of CuO nanoparticles into LSCF electrodes. CuO infiltrated electrodes reduced the interfacial polarization resistance from 2.27 Ω cm2 to 1.5 Ω cm2 at 600 °C and increased the peak power density from 0.54 W cm−2 to 0.72 W cm−2 at 650 °C. Electrochemical impedance spectroscopy indicated that the reduced resistance was due to the shrinkage of the low frequency arc, which is associated with the electrochemical surface exchange reaction.

PHYSICALLY-BASED DECONVOLUTION OF IMPEDANCE SPECTRA: INTERPRETATION, FITTING AND VALIDATION OF A NUMERICAL MODEL FOR LANTHANUM STRONTIUM COBALT FERRITE-BASED SOLID OXIDE FUEL CELLS

In this study, a physically-based model for the interpretation of the impedance spectra of an anode-supported LSCF/GDC/YSZ/Ni:YSZ solid oxide fuel cell is presented. The model locally describes transport and reaction phenomena within the cell components through mass conservation equations. The microstructural properties of the electrodes are predicted through numerical three-dimensional reconstruction of the microstructure, with input parameters obtained from the analysis of SEM pictures of each layer. Simulations show that the model reproduces impedance spectra obtained in different operating conditions with the same set of fitting parameters, comprising material-specific kinetic constants and electrochemical capacitances, which fairly agree with independent literature data and a previous analysis of the spectra through DRT. The model allows for the deconvolution and quantification of the characteristic resistance and frequency of the different physical processes that build up the impedance of the cell. In particular, 7 processes are identified: charge-transfer reactions between LSCF/GDC, GDC/YSZ and Ni/YSZ interfaces appear in the high-frequency range, the medium-frequency feature is due the oxygen reduction reaction and the gas diffusion in the anode, while the low-frequency arc is mainly due to the gas conversion in the anodic channel. An additional low frequency contribution (<1Hz), not considered in the model, is observed and tentatively attributed to the adsorption of oxygen onto the LSCF surface. Simulation results suggest that more efforts must be dedicated to characterize and improve the oxygen transfer at the LSCF/GDC and GDC/YSZ interfaces. The study shows that a quantitative interpretation of impedance spectra is possible with a reduced number of fitting parameters when a physically-based approach is adopted, making the model an attractive tool for diagnostic purposes.

Nonlinear Impedance Analysis of La0.4Sr0.6Co0.2Fe0.8O3-δ Thin Film Oxygen Electrodes

Linear and nonlinear electrochemical impedance spectroscopy (EIS, NLEIS) were used to study 20 nm thin film La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF-6428) electrodes at 600°C in oxygen environments. LSCF films were epitaxially deposited on single crystal yttria-stabilized zirconia (YSZ) with a 5 nm gadolinium-doped ceria (GDC) protective interlayer. Impedance measurements reveal an oxygen storage capacity similar to independent thermogravimetry measurements on semi-porous pellets. However, the impedance data fail to obey a homogeneous semiconductor point-defect model. Two consistent scenarios were considered: a homogeneous film with non-ideal thermodynamics (constrained by thermogravimetry measurements), or an inhomogeneous film (constrained by a semiconductor point-defect model with a Sr maldistribution). The latter interpretation suggests that gradients in Sr composition would have to extend beyond the space-charge region of the gas-electrode interface. While there is growing evidence supporting an equilibrium Sr segregation at the LSCF surface monolayer, a long-range, non-equilibrium Sr stratification caused by electrode processing conditions offers a possible explanation for the large volume of highly reducible LSCF. Additionally, all thin films exhibited fluctuations in both linear and nonlinear impedance over the hundred-hour measurement period. This behavior is inconsistent with changes solely in the surface rate coefficient and possibly caused by variations in the surface thermodynamics over exposure time.

Highly active YSB infiltrated LSCF cathode for proton conducting solid oxide fuel cells

An oxygen ion conductor, Y0.25Bi0.75O1.5 (YSB), infiltrated La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) is prepared as the electrode of proton conducting solid oxide fuel cells (H–SOFCs). The YSB is deposited onto LSCF surface by infiltration way at 600 °C with a good chemical compatibility. The electrochemical performance of YSB infiltrated LSCF electrode is evaluated regarding the infiltration process. When the loading of YSB increases, the interfacial polarization resistance (RP) of the symmetric cell decreases gradually and then increases. The results of symmetric cell and single cell test indicate that the electrochemical activity of YSB infiltrated LSCF cathode is higher than that using traditional mixed SSC-SDC cathode. The encouraging results open a promising strategy to develop cathode materials for H–SOFCs at low temperature.

ChemInform Abstract: B‐Site Metal (Pd, Pt, Ag, Cu, Zn, Ni) Promoted La1‐xSrxCo1‐yFeyO3‐ δ Perovskite Oxides as Cathodes for IT‐SOFCs

AbstractReview: 77 refs.

Fundamental Impact of Humidity on SOFC Cathode Degradation

The durability of SOFCs under real working conditions is still an issue for commercial deployment. In particular cathode exposure to atmospheric air contaminants, such as humidity, can result in long-term performance degradation issues. Therefore, a fundamental understanding of the interaction between water molecules and cathodes is essential to resolve this issue and further enhance cathode durability. To study the effects of humidity on the ORR, we used insitu 18O isotope exchange techniques to probe the exchange of water with two of the most common SOFC cathode materials, LSM and LSCF. In this experiment, heavy water, D2O (mass/charge ratio of m/z=20), is used to avoid overlapping of H2O and 18O2 cracking fraction (m/z=18). Temperature programmed isotope exchange measurements were performed to comprehensively study the interaction of water with the cathode surface as a function of temperature, oxygen partial pressure, and water vapor concentration. The results suggest that H2O and O2 share the same surface exchange sites. Therefore, the presence of H2O competes with O2 for the available surface sites. Our findings show that H2O prefers to exchange with LSM and LSCF at a lower temperature, ~300-450°C. For LSM, O2 is more favorable than H2O to be adsorbed on LSM surface and the presence of O2 limits H2O exchange with LSM. H2O has two different exchange mechanisms to react with the LSCF surface, and each mechanism dominates in a different temperature region. The data are summarized to a Temperature-PO2 diagram to visualize the dominant reactions at temperature and PO2 for the two cathode materials.

B-Site Metal (Pd, Pt, Ag, Cu, Zn, Ni) Promoted La1−xSrxCo1−yFeyO3–δ Perovskite Oxides as Cathodes for IT-SOFCs

Perovskite oxides La1−xSrxCo1−yFeyO3–δ (LSCF) have been extensively investigated and developed as cathode materials for intermediate temperature solid oxide fuel cells (IT-SOFCs) due to mixed ionic–electronic conductivity and high electrooxygen reduction activity for oxygen reduction. Recent literature investigations show that cathode performances can be improved by metal surface modification or B-site substitution on LSCF. Although the specific reaction mechanism needs to be further investigated, the promoting effect of metal species in enhancing oxygen surface exchange and oxygen bulk diffusion is well recognized. To our knowledge, no previous reviews dealing with the effect of metal promotion on the cathodic performances of LSCF materials have been reported. In the present review, recent progresses on metal (Pd, Pt, Ag, Cu, Zn, Ni) promotion of LSCF are discussed focusing on two main aspects, the different synthesis approaches used (infiltration, deposition, solid state reaction, one pot citrate method) and the effects of metal promotion on structural properties, oxygen vacancies content and cathodic performances. The novelty of the work lies in the fact that the metal promotion at the B-site is discussed in detail, pointing at the effects produced by two different approaches, the LSCF surface modification by the metal or the metal ion substitution at the B-site of the perovskite. Moreover, for the first time in a review article, the importance of the combined effects of oxygen dissociation rate and interfacial oxygen transfer rate between the metal phase and the cathode phase is addressed for metal-promoted LSCF and compared with the un-promoted oxides. Perspectives on new research directions are shortly given in the conclusion.

Enhanced catalytic activity toward O₂ reduction on Pt-modified La₁-xSrxCo₁-yFeyO₃-δ cathode: a combination study of first-principles calculation and experiment.

Using the first-principles calculation and the electronic conductivity relaxation (ECR) experimental technique, we investigated the adsorption and dissociation behaviors of O2 on Pt-modified La0.625Sr0.375Co0.25Fe0.75O3-δ (LSCF) surface. Toward the O2 reduction, the calculation results show that the perfect LSCF (100) surface is catalytically less active than both the defective (100) surface and the perfect (110) surface. O2 molecule can weakly adsorb on the perfect LSCF (100) surface with a small adsorption energy of about -0.30 eV, but the dissociation energy barrier of the O2 molecule is about 1.33-1.43 eV. Doping of Pt cluster on the LSCF (100) surface can remarkably enhance its catalytic activity. The adsorption energies of O2 molecules become -1.16 and -1.89 eV for the interfacial Feint site and the Ptbri bridge site of Pt4-cluster, respectively. Meanwhile, the dissociation energy barriers are reduced to 0.37 and 0.53 eV, respectively. The migration energy barrier of the dissociated oxygen from the interfacial Pt to the LSCF surface is 0.66 eV, and it is 2.58 eV from the top site of the Pt cluster to the interfacial Pt site, suggesting that it is extremely difficult for oxygen to migrate over the Pt cluster. The Bader charge analysis results further indicate that the charges transferring from Pt cluster to LSCF surface promote the adsorption and dissociation of O2 molecules. Experimentally, a dramatic decrease of the surface oxygen exchange relaxation time was observed on Pt-modified LSCF cathode, with a chemical surface exchange coefficient increased from 6.05 × 10(-5) cm/s of the bare LSCF cathode to 4.04 × 10(-4) cm/s of the Pt-modified LSCF cathode, agreeing very well with our theoretical predictions.

Oxygen incorporation at the three-phase boundary of LSCF–SDC composite

Oxygen reduction at LSCF–SDC (La0.6Sr0.4Co0.2Fe0.8O3 − δ–Sm0.2Ce0.8O1.9) composite cathode might take place at the LSCF-gas two-phase interface (2 PB) and the LSCF–SDC-gas three-phase boundary (3 PB). A method is developed to determine the oxygen incorporation rate and the amount of incorporated oxygen at 3 PB using the electrical conductivity relaxation technique. The obtained results are powerful supports to the viewpoint that oxygen incorporation at 3 PB is much more facile than that at 2 PB. The amount of oxygen incorporated absolutely at 3 PB plays a dominating role in the total process, which actually contributes an average of more than 70% when only 4.5 vol. % SDC is added to LSCF. The incorporation rate at 3 PB is found to be affected not only by the 3 PB length but also the diffusion of oxygen species on the LSCF surface. An effective surface diffusion length of about 1.5 μm is suggested by the relation between the rate, 3 PB length and LSCF surface area.