Infiltrated multiscale porous cathode for proton-conducting solid oxide fuel cells

A Sm_0.5Sr_0.5CoO_3−δ (SSC)-BaZr_0.1Ce_0.7Y_0.2O_3−δ (BZCY) composite cathode with multiscale porous structure was successfully fabricated through infiltration for proton-conducting solid oxide fuel cells (SOFCs). The multiscale porous SSC catalyst was coated on the BZCY cathode backbones. Single cells with such composite cathode demonstrated peak power densities of 0.289, 0.383, and 0.491 W cm⁻² at 600, 650, 700 °C, respectively. Cell polarization resistances were found to be as low as 0.388, 0.162, and 0.064 Ω cm² at 600, 650 and 700 °C, respectively. Compared with the infiltrated multiscale porous cathode, cells with screen-printed SSC-BZCY composite cathode showed much higher polarization resistance of 0.912 Ω cm² at 600 °C. This work has demonstrated a promising approach in fabricating high performance proton-conducting SOFCs.     

A simple Ce-doping strategy to enhance stability of hybrid symmetrical electrode for solid oxide fuel cells

Symmetrical solid oxide fuel cell (SSOFC) is a simple and very promising cell for the rest of the most important commercialization process, which has been longing for stable and efficient symmetrical electrodes, from single-phase perovskites to reducible perovskites with in-situ exsolved metal nanoparticles. Herein, we present a new-type hybrid symmetrical electrode consisting of two different perovskite phases for SSOFC, which interact by dynamic compositional change and accordingly improve the electrochemical activity. Furthermore, a simple Ce-doping strategy is successfully developed to solve the redox stability issue of the hybrid symmetrical electrode for SSOFC. Typical Gd_0.65Sr_0.35Co_0.25Fe_0.75O_3-δ (GSCF) consisting of a cubic perovskite phase and an orthorhombic perovskite phase is chosen as a proof-of-concept. Gd_0.65Sr_0.35(Co_0.25Fe_0.75)_0.9Ce_0.1O_3-δ (Ce-GSCF) with an optimized Ce content of only 10% exhibit the enhanced chemical and thermal stability, consisting of a cubic perovskite phase, an orthorhombic perovskite phase and an in-situ exsolved cubic fluorite phase (GDC). More importantly, Ce-GSCF exhibits very high stability in H₂ at 700 °C and a dramatical reduction of averaged thermal expansion coefficient from 19.5 × 10⁻⁶ K⁻¹ to 16.4 × 10⁻⁶ K⁻¹. The single-cell with Ce-GSCF hybrid symmetrical electrode reaches a high maximum power density of 224 mW/cm² at 700 °C, and can work stably for 180 h without any degradation, indicating that the simple Ce-doping strategy is promising to improve stability of hybrid symmetrical electrode for SOFCs.     

Sr2Fe4/3Mo2/3O6 as anodes for solid oxide fuel cells

Sr₂Fe_4/3Mo_2/3O₆ has been synthesized by a combustion method in air. It shows a single cubic perovskite structure after being reduced in wet H₂ at 800 °C and demonstrates a metallic conducting behavior in reducing atmospheres at mediate temperatures. Its conductivity value at 800 °C in wet H₂ (3% H₂O) is about 16 S cm⁻¹. This material exhibits remarkable electrochemical activity and stability in H₂. Without a ceria interlayer, maximum power density (P_max) of 547 mW cm⁻² is achieved at 800 °C with wet H₂ (3% H₂O) as fuel and ambient air as oxidant in the single cell with the configuration of Sr₂Fe_4/3Mo_2/3O₆|La_0.8Sr_0.2Ga_0.83Mg_0.17O₃ (LSGM)| La_0.6Sr_0.4Co_0.2Fe_0.8O₃ (LSCF). The P_max even increases to 595 mW cm⁻² when the cell is operated at a constant current load at 800 °C for additional 15 h. This anode material also shows carbon resistance and sulfur tolerance. The P_max is about 130 mW cm⁻² in wet CH₄ (3% H₂O) and 472 mW cm⁻² in H₂ with 100 ppm H₂S. The cell performance can be effectively recovered after changing the fuel gas back to H₂.     

Investigation of layered Ni0.8Co0.15Al0.05LiO2 in electrode for low-temperature solid oxide fuel cells

A symmetrical cell composed of Ce_0.9Gd_0.1O_2?δ electrolyte is constructed with 0.5 mm thickness and Ni_0.8Co_0.15Al_0.05LiO₂ (NCAL)-foam Ni composite electrodes. Electrochemical performance of the cell and electrochemical impedance spectra (EIS) are measured using the three-electrode method. The maximum power densities of the cell are 93.6 and 159.7 mW cm^?2 at 500 and 550 °C, respectively. The polarization resistances of the cathode are 0.393 and 0.729 Ω cm^?2 at 550 and 500 °C, indicating that NCAL has good ORR activity. HT-XRD results for NCAL do not show phase transitions or any additional new phases at elevated temperatures, indicating that NCAL has a stable phase structure. The surface characteristics of the NCAL powders are studied by XPS and FTIR. The results reveal that Li₂CO₃ and the cation-disordered “NiO-like” phase are formed on the surface of the layered NCAL structure due to prolonged exposure to air and contain a large number of oxygen vacancies. The cation-disordered “NiO-like” phase and Li₂CO₃ composite in the melt and partial melt states in the high temperature region are considered to possess very high ionic conductivity and lower activation energy for oxygen reduction reactions.     

A promising NiCo2O4 protective coating for metallic interconnects of solid oxide fuel cells

The NiCo₂O₄ spinel coating is applied onto the surfaces of the SUS 430 ferritic stainless steel by the sol-gel process; and the coated alloy, together with the uncoated as a comparison, is cyclically oxidized in air at 800 °C for 200 h. The oxidation behavior and oxide scale microstructure as well as the electrical property are characterized. The results indicate that the oxidation resistance is significantly enhanced by the protective coating with a parabolic rate constant of 8.1 × 10⁻¹⁵ g² cm⁻⁴ s⁻¹, while the electrical conductivity is considerably improved due to inhibited growth of resistive Cr₂O₃ and the formation of conductive spinel phases in the oxide scale.     

Bi0.5Sr0.5MnO3 as cathode material for intermediate-temperature solid oxide fuel cells

Bi_0.5Sr_0.5MnO₃ (BSM), a manganite-based perovskite, has been investigated as a new cathode material for intermediate-temperature solid oxide fuel cells (SOFCs). The average thermal-expansion coefficient of BSM is 14 × 10⁻⁶ K⁻¹, close to that of the typical electrolyte material. Its electrical conductivity is 82-200 S cm⁻¹ over the temperature range of 600-800 °C, and the oxygen ionic conductivity is about 2.0 × 10⁻⁴ S cm⁻¹ at 800 °C. Although the cathodic polarization behavior of BSM is similar to that of lanthanum strontium manganite (LSM), the interfacial polarization resistance of BSM is substantially lower than that of LSM. The cathode polarization resistance of BSM is only 0.4 Ω cm² at 700 °C and it decreases to 0.17 Ω cm² when SDC is added to form a BSM-SDC composite cathode. Peak power densities of single cells using a pure BSM cathode and a BSM-SDC composite electrode are 277 and 349 mW cm² at 600 °C, respectively, which are much higher than those obtained with LSM-based cathode. The high electrochemical performance indicates that BSM can be a promising cathode material for intermediate-temperature SOFCs.     

Preparation and electrochemical performance of Pr2Ni0.6Cu0.4O4 cathode materials for intermediate-temperature solid oxide fuel cells

Cathode material Pr₂Ni_0.6Cu_0.4O₄ (PNCO) for intermediate-temperature solid oxide fuel cells (IT-SOFCs) is synthesized by a glycine-nitrate process using Pr₆O₁₁, NiO, and CuO powders as raw materials. X-ray diffraction analysis reveals that nanosized Pr₂Ni_0.6Cu_0.4O₄ powders with K₂NiF₄-type structure can be obtained from calcining the precursors at 1000 °C for 3 h. Scanning electron microscopy shows that the sintered PNCO samples have porous microstructure with a porosity of more than 30% and grain size smaller than 2 μm. A maximum conductivity of 130 S cm⁻¹ is obtained from the PNCO samples sintered at 1050 °C. A single fuel cell based on the PNCO cathode with 30 μm Sm_0.2Ce_0.8O_1.9 (SCO) electrolyte film and a 1 mm NiO-SCO anode support is constructed. The ohmic resistance of the single Ni-SCO/SCO/PNCO cell is 0.08 Ω cm² and the area specific resistance (ASR) value is 0.19 Ω cm² at 800 °C. Cell performance was also tested using humidified hydrogen (3% H₂O) as fuel and air as oxidant. The single cell shows an open circuit voltage of 0.82 V and 0.75 V at 700 °C and 800 °C, respectively. Maximum power density is 238 mW cm⁻² and 308 mW cm⁻² at 700 °C and 800 °C, respectively. The preliminary tests have shown that Pr₂Ni_1−xCu_xO₄materials can be a good candidate for cathode materials of IT-SOFCs.     

Ni-Sm2O3 cermet anodes for intermediate-temperature solid oxide fuel cells with stabilized zirconia electrolytes

Ni-LnO_x cermets (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd), in which LnO_x is not an oxygen ion conductor, have shown high performance as the anodes for low-temperature solid oxide fuel cells (SOFCs) with doped ceria electrolytes. In this work, Ni-Sm₂O₃ cermets are primarily investigated as the anodes for intermediate-temperature SOFCs with scandia stabilized zirconia (ScSZ) electrolytes. The electrochemical performances of the Ni-Sm₂O₃ anodes are characterized using single cells with ScSZ electrolytes and LSM-YSB composite cathodes. The Ni-Sm₂O₃ anodes exhibit relatively lower performance, compared with that reported Ni-SDC (samaria doped ceria) and Ni-YSZ (yttria stabilized zirconia) anodes, the state-of-the-art electrodes for SOFCs based on zirconia electrolytes. The relatively low performance is possibly due to the solid-state reaction between Sm₂O₃ and ScSZ in fuel cell fabrication processes. By depositing a thin interlayer between the Ni-Sm₂O₃ anode and the ScSZ electrolyte, the performance is substantially improved. Single cells with a Ni-SDC interlayer show stable open circuit voltage, generate peak power density of 410 mW cm⁻² at 700 °C, and the interfacial polarization is about 0.7 Ω cm².     

Electrochemical reduction of CO2 in solid oxide electrolysis cells

This paper describes results on the electrochemical reduction of carbon dioxide using the same device as the typical planar nickel-YSZ cermet electrode supported solid oxide fuel cells (H₂-CO₂, Ni-YSZ|YSZ|LSCF-GDC, LSCF, air). Operation in both the fuel cell and the electrolysis mode indicates that the electrodes could work reversibly for the charge transfer processes. An electrolysis current density of ≈1 A cm⁻² is observed at 800 °C and 1.3 V for an inlet mixtures of 25% H₂-75% CO₂. Mass spectra measurement suggests that the nickel-YSZ cermet electrode is highly effective for reduction of CO₂ to CO. Analysis of the gas transport in the porous electrode and the adsorption/desorption process over the nickel surface indicates that the cathodic reactions are probably dominated by the reduction of steam to hydrogen, whereas carbon monoxide is mainly produced via the reverse water gas shift reaction.     

Structural,electrical, and electrochemical properties of cobalt-doped NiFe2O4 as a potential cathode material for solid oxide fuel cells

In this work, Co-doped NiFe₂O₄ spinels (NFCO-x) are successfully fabricated and characterized as possible cathode materials for the intermediate-temperature solid oxide fuel cells (SOFC). Results of the binding energy calculations using the density functional theory suggest that the reverse spinel structure is stable when Co³⁺ occupies the octahedral interstitial sites. Total and ionic-only conductivities indicate that NFCO-x are a kind of mixed electronic-ionic conductors. Ionic transferring numbers are approximately 0.049 and 0.006 for NFCO-0.1 and NFCO-0.5, respectively, measured at 700 °C in air. Co dopant in the NFCO-x improves the electronic conductivity at the expense of the ionic conductivity. For NFCO-0.5, electronic and ionic conductivities are approximately 0.24 and 9.6 × 10⁻⁴ S cm⁻¹, respectively, measured also at 700 °C in air. Unlike behaviour of the conductivities, the polarization resistance of symmetric cells with NFCO-x electrodes decreases when increasing the Co content (x) to a certain level, and then increases. The cell containing the NFCO-0.5 electrode exhibits the lowest polarization resistance (R_p), which is approximately 1.51 Ω cm² at 650 °C. For single cells, the maximum power density is 320 mW cm⁻² measured at 650 °C using a 38-μm-thick SDC electrolyte and an NFCO-0.5 cathode.     

Layered GdBa0.5Sr0.5Co2O5+δ as a cathode for intermediate-temperature solid oxide fuel cells

The layered GdBa_0.5Sr_0.5Co₂O_5+δ (GBSC) perovskite oxides are synthesized by Pechini method and investigated as a novel cathode material for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The single cell of NiO–SDC (Sm_0.2Ce_0.8O_1.9)/SDC (20 μm)/GBSC (10 μm) is operated from 550 to 700 °C fed with humidified H₂ as fuel and the static air as oxidant. An open circuit voltage of 0.8 V and a maximum power density of 725 mW cm⁻² are achieved at 700 °C. The interfacial polarization resistance is as low as 0.88, 0.29, 0.13 and 0.05 Ω cm² at 550, 600, 650 and 700 °C, respectively. The ratio of polarization resistance to total cell resistance decreases with the increase in the operating temperature, from 60% at 550 °C to 21% at 700 °C, respectively. The experimental results indicate that GBSC is a promising cathode material for IT-SOFCs.     

Preparation and electrochemical properties of strontium doped Pr2NiO4 cathode materials for intermediate-temperature solid oxide fuel cells

Pr_2−xSr_xNiO₄ (PSNO, x = 0.3, 0.5 and 0.8) cathode materials for intermediate-temperature solid oxide fuel cell (IT-SOFC) were synthesized by a glycine-nitrate process using Pr₆O₁₁, Ni(NO₃)₂·6H₂O and SrCO₃ powders as raw materials. Phase structure of the synthesized powders was characterized by X-ray diffraction analysis (XRD). Microstructure of the sintered PSNO samples was observed and thermal expansion coefficient (TEC) and electrical conductivity were investigated. Electrochemical impedance spectroscopy (EIS) measurement of the PSNO materials on Sm_0.2Ce_0.8O_1.9 (SCO) electrolyte was carried out, and single cells based on the PSNO cathodes were also assembled and their performances were tested. The results show that the synthesized PSNO powders have pure K₂NiF₄-type structure and the PSNO materials are chemically stable with Sm_0.2Ce_0.8O_1.9 (SCO) electrolyte. The sintered PSNO samples have porous and fine microstructure with pore size smaller than 1 μm. Average thermal expansion coefficient of the PSNO materials is about 12–13 × 10⁻⁶ K⁻¹ at 200–800 °C and the electrical conductivity is in the range of 70–120 Scm⁻¹ at 800 °C. Area specific resistance (ASR) of the Pr_2−xSr_xNiO₄ materials on SCO electrolyte is 0.407 Ωcm², 0.126 Ωcm² and 0.112 Ωcm² for x = 0.3, 0.5 and 0.8 at 800 °C, respectively. Maximum open circuit voltage (OCV) and power density of the single NiO-SCO/SCO/PSNO cells are 0.75 V and 298 mWcm⁻² at 700 °C, respectively, which indicates that Pr_2−xSr_xNiO₄ may be a potential cathode material for IT-SOFC.     

Preparation and electrochemical properties of Sr-doped Nd2NiO4 cathode materials for intermediate-temperature solid oxide fuel cells

Cathode materials Nd_2 − xSr_xNiO₄ were prepared by the glycine-nitrate process and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), AC impendence spectroscopy and DC polarization method, respectively. The results show that no reaction occurred between the electrode and the CGO electrolyte at 1100 °C and the electrode formed good contact with the electrolyte after being sintered at 1000 °C for 4 h. The rate-limiting step for oxygen reduction reaction on Nd_1.6Sr_0.4NiO₄ electrode changed with oxygen partial pressure and measurement temperature. The Nd_1.6Sr_0.4NiO₄ electrode gave a polarization resistance of 0.93 Ω cm² at 700 °C in air, which indicates that Nd_2 − xSr_xNiO₄ electrode is a promising cathode material for intermediate-temperature solid oxide fuel cell (IT-SOFC).     

The heterogeneous electrolyte of CuFeO2 nano-flakes composited with flower-shaped ZnO for advanced solid oxide fuel cells

The flower-shaped ZnO was synthesized to form composite with the delafossite structure CuFeO₂. The composite heterojunction formed for the ZnO-CuFeO₂ composite material demonstrates a profound significance for exploring novel materials in solid oxide fuel cell (SOFC) field. At 550 °C, power outputs of 300 mW cm^?2 and 468 mW cm^?2 were achieved for SOFC devices using pure ZnO and composite with CuFeO₂ as the electrolytes, respectively. The composite showed a good performance at low temperatures, for instance, it showed a power output of 148 mW cm^?2 at 430 °C. The studies on photocurrent-time curves with visible light on/off irradiation provided an evidence for electron-hole separation. The heterojunctions separate holes and electrons, preventing short-circuiting while used in the SOFC device. These results demonstrate that introducing the heterojunctions in the electrolyte is an innovative approach for advanced SOFCs.     

Cobalt-free layered perovskite GdBaFe2O5+x as a novel cathode for intermediate temperature solid oxide fuel cells

A cobalt-free layered perovskite oxide, GdBaFe₂O_5+x (GBF), was investigated as a novel cathode for intermediate temperature solid oxide fuel cells (IT-SOFCs). Area-specific resistance (ASR) of GBF was measured by impedance spectroscopy in a symmetrical cell. The observed ASR was as low as 0.15 Ω cm² at 700 °C and 0.39 Ω cm² at 650 °C, respectively. A laboratory sized Sm_0.2Ce_0.8O_1.9 (SDC)-based tri-layer cell of NiO-SDC/SDC/GBF was tested under intermediate temperature conditions of 550-700 °C with humidified H₂ (∼3% H₂O) as a fuel and the static ambient air as an oxidant. A maximal power density of 861 mW cm⁻² was achieved at 700 °C. The electrode polarization resistance was as low as 0.57, 0.22, 0.13 and 0.08 Ω cm² at 550, 600, 650 and 700 °C, respectively. The experimental results indicate that the layered perovskite GBF is a promising cathode candidate for IT-SOFCs.     

High performance and stability of nanocomposite oxygen electrode for solid oxide cells

Solid oxide electrochemical cell (SOC) is a highly promising alternative for fuel conversion and power-to-gas due to its high efficiency and low emission. However, degradation resulting from the electrolyte-electrode interface is a major challenge in both fuel cell mode and electrolysis mode. Here, a co-sintering tri-layer structure cell with nanocomposite oxygen electrode is developed to mitigate the interface issue. A 10 × 10 cm² NiO/YSZ||YSZ||YSZ-La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF) cell has been conducted under different fuels in SOFC mode. A power density output of 558 mW/cm² @0.7 V-800 °C in wet H₂ and a durability of 300 h in simulated syngas have been obtained. The performance of LSF, LSCF and SSC oxygen electrodes have been studied in both SOFC and SOEC modes. It suggests that three oxygen electrodes have an order of SSC > LSCF > LSF in electrochemical performance, and an opposite order in stability of SOEC. The degradation of the LSCF and SSC can be derived from the solid-state reactions at the interface between Co-containing perovskites and YSZ during operation. It demonstrates that GDC and Ag modification can enhance the oxygen electrode stability by impeding the solid-state reactions and the nanoparticles sintering. Results suggest that GDC has a negative effect on the cell performance and Ag has a positive effect, implying that enhancing the electric conductivity of YSZ-LSCF is the key to improve the cell performance. Moreover, cell with YSZ-SFM/GDC has been applied in CH₄ assisted SOEC process (CH₄-SOEC), in which a significant reduction of electricity consume can be realized.     

Effects of chromium poisoning on the long-term oxygen exchange kinetics of the solid oxide fuel cell cathode materials La0.6Sr0.4CoO3 and Nd2NiO4

The influence of chromium poisoning on the long-term stability of the oxygen exchange kinetics of the promising IT-SOFC cathode materials La_0.6Sr_0.4CoO_3−δ (LSC) and Nd₂NiO_4+δ (NDN) is investigated in-situ by dc-conductivity relaxation experiments. The as-prepared LSC and NDN samples show high chemical oxygen surface exchange coefficients k_chem. After the deposition of a 10 nm thick Cr-layer onto the surface, k_chem of LSC decreases to 50% of the initial value. Additional chromium deposition of 20 nm on LSC leads to a further decrease of k_chem to 27% of the initial value. In contrast, the effect of a 10 nm thick Cr-layer on k_chem of NDN is negligible. Even with additional 20 nm of chromium and a total testing time of 1750 h, the nickelate retains a k_chem of 60% of the initial value. X-ray photoelectron spectroscopy (XPS) of the degraded. LSC shows a significantly altered surface cation composition with Sr-enrichment down to 30 nm depth while XPS analysis of the degraded NDN reveals a thin surface zone of approximately 30 nm containing nickel and chromium. In contrast to LSC, the changes in the surface composition of NDN due to Cr-poisoning ultimately had only a minor influence on the surface exchange properties.     

Nanoscale bismuth oxide impregnated (La,Sr)MnO3 cathodes for intermediate-temperature solid oxide fuel cells

Bismuth oxide based oxygen ion conductors are incorporated into (La,Sr)MnO₃ (LSM), the classical cathode material for solid oxide fuel cells (SOFC), to improve the cathode performance. Yttria-stabilized bismuth oxide (YSB) is taken as an example and is impregnated into a preformed porous LSM frame, forming a highly active cathode for intermediate-temperature SOFCs (IT-SOFCs) with doped ceria electrolytes. X-ray diffraction indicates that YSB is chemically compatible with LSM at intermediate temperatures below 800 °C. The impregnated YSB particles are nanosized and are deposited on the surface of the framework. Significant performance improvement is achieved by introducing nanosized YSB into the LSM electrodes. At 600 °C, the interfacial polarization resistance under open-circuit conditions for electrodes impregnated with 50% YSB is only 1.3% of the original value for a pure LSM electrode. The resistance is further reduced dramatically when current is passed through. In addition, the YSB impregnated LSM electrodes has the highest electrochemical performance among those based on LSM. Single cell with 25% of YSB impregnated LSM cathode generates maximum power density of 300 mW cm⁻² at 600 °C, indicating the promise of using LSM-based electrodes for IT-SOFC.     

High performance layered SmBa0.5Sr0.5Co2O5+δ cathode for intermediate-temperature solid oxide fuel cells

The layered SmBa_0.5Sr_0.5Co₂O_5+δ (SBSC) perovskite oxide is synthesized by the Pechini method and investigated as a novel cathode material for intermediate-temperature solid oxide fuel cells (IT-SOFCs). A laboratory-sized Sm_0.2Ce_0.8O_1.9 (SDC)-based tri-layer cell of NiO–SDC/SDC/SBSC is operated from 500 to 700 °C fed with humidified H₂ (3% H₂O) as a fuel and the static ambient air as oxidant. A maximum power density of 1147 mW cm⁻² is achieved at 700 °C. The interfacial polarization resistance is as low as 1.01, 0.38, 0.16, 0.06 and 0.03 Ω cm² at 500, 550, 600, 650 and 700 °C, respectively. The experimental results indicate that SBSC is a very promising cathode material for IT-SOFCs.     

Advance fuel cells using Al2O3-nNaAlO2 composite as ion-conducting membrane

In present work, we reported an novel oxide-salt Al₂O₃NaAlO₂ composite, which was prepared by mixing Al₂O₃ and Na₂CO₃ two phase materials in different weight ratio, and then sintering at 1100 °C. The X-ray diffraction pattern, scanning-electron microscope and impedance spectra are applied to characterize the crystal structure, morphology and electrical properties of the Al₂O₃NaAlO₂ composite. The Al₂O₃NaAlO₂ composite as electrolyte membrane was sandwiched by two pieces of Ni_0.8Co_0.15Al_0.05Li-oxide (NCAL) electrode layer to construct advanced fuel cell. Optimizing the weight ratio of Al₂O₃ and NaAlO₂, such cell delivered an highest power density of 789 mW/cm² and an open circuit voltage (V_oc) of 1.13 V at 575 °C. The superior performance is mainly due to the excellent ion-conducting of Al₂O₃NaAlO₂ composites and the outstanding catalysis activity of the NCAL eletrodes. The EIS results revealed that the Al₂O₃NaAlO₂ composite possessed superior ionic conductivity of 0.121 S/cm at 575 °C. The interfacial effects between oxide-salt two phase including space-charge and structural misfit at the interface region dominated the ion transport for Al₂O₃NaAlO₂ composite.