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Ruddlesden-Popper (R–P) structure oxide has been widely used as the electrode material in low temperature solid oxide fuel cells (LT-SOFCs) because of its high catalytic activity and excellent oxygen transport performance, while the studies on this material served as the electrolyte of LT-SOFCs is rarely reported. Herein, the R–P P-type semiconductor Sm 1.2 Sr 0·8 Ni 0·6 Fe 0·4 O 4+δ (SSNF) oxide material was prepared and then used as electrolyte by constructing P–N heterostructure with the N-type semiconductor Sm 0.075 Nd 0.075 Ce 0·85 O 2-δ (SNDC) oxide material. Experimental results showed that the developed 5SSNF-5SNDC composite electrolyte exhibited a high ionic conductivity of 0.201 S·cm−1 along with remarkable fuel cell power density of 1056 mW·cm−2 at 550·°C. The constructed P–N heterostructure helps to improve the oxygen ion conductivity and thus the electrochemical properties. These results demonstrate that P–N heterojunctions constructed from oxide materials with highly catalytically active R–P structures exhibit excellent electrolyte performance. This work provides a new perspective for developing advanced electrolytes of LT-SOFCs. [Display omitted] • The composite electrolyte has a high oxygen vacancy. • The fuel cell device produces a maximum power density of 1056 mW cm−2 at 550 °C. • The composite electrolyte has a significant ionic conductivity of 0.201 S cm−1. • Ion migration was enhanced by constructing P–N heterojunctions. [ABSTRACT FROM AUTHOR]

Abstract: PrBaCo2O5+δ –Ce0.8Sm0.2O1.9 (PBCO–SDC) composite material are prepared and characterized as cathode for intermediate temperature solid oxide fuel cells (IT-SOFCs). The powder X-ray diffraction result proves that there are no obvious reaction between the PBCO and SDC after calcination at 1100°C for 3h. AC impedance spectra based on SDC electrolyte measured at intermediate temperatures shows that the addition of SDC to PBCO improved remarkably the electrochemical performance of a PBCO cathode, and that a PBCO–30SDC cathode exhibits the best electrochemical performance in the PBCO–xSDC system. The total interfacial resistances R p is the smallest when the content of SDC is 30wt%, where the value is 0.035Ωcm2 at 750°C, 0.072Ωcm2 at 700°C, and 0.148Ωcm2 at 650°C, much lower than the corresponding interfacial resistance for pure PBCO. The maximum power density of an anode-supported single cell with PBCO–30SDC cathode, Ni–SDC anode, and dense thin SDC/LSGM (La0.9Sr0.1Ga0.8Mg0.2O3−δ )/SDC tri-layer electrolyte are 364, 521 and 741mWcm−2 at 700, 750 and 800°C, respectively. [Copyright &y& Elsevier]

Abstract: The BaCo0.7Fe0.3− y Nb y O3− δ oxides (BCFNy, y =0.00–0.12) were synthesized by the conventional solid state reaction process and investigated as a novel cathode for intermediate temperature solid oxide fuel cells(IT-SOFCs). Cubic perovskite, with enhanced phase stability at higher Nb concentration, was obtained at y ⩾0.04. The unit cell volumes increased with y, reached a maximum at y =0.10, and then decreased. The niobium doping concentration also had a significant effect on the electrochemical performance of BCFNy materials. Among the various BCFNy oxides tested, BCFN0.10 possessed the smallest interfacial polarization resistance (R p). The R p was as low as 0.9406, 0.1300, 0.0211, and 0.0082Ωcm2 at 500, 600, 700, and 800°C, respectively. With a 220μm-thick Sm0.2Ce0.1O1.9 (SDC) as electrolyte and BCFN0.10 as the cathode, a fuel cell provides maximum power densities of 202, 350, 569, 820, and 1006mWcm−2 at 600, 650, 700, 750, and 800°C, respectively. The encouraging results suggested that BCFN0.10 was a very promising cathode material for IT-SOFCs. [Copyright &y& Elsevier]

Abstract: PrBaCo2O5+δ (PBCO) powder was prepared by a combined EDTA and citrate complexing method. The electrochemical performance of PBCO as a cathode for intermediate-temperature solid oxide fuel cells (IT-SOFCs) was evaluated. A porous layer of PBCO was deposited on a 42μm thick electrolyte consisting of Ce0.8Sm0.2O1.9 (SDC), prepared by a dry-pressing process. A fuel cell with a structure PBCO/SDC/Ni-SDC provides a maximum power density of 866, 583, 313 and 115mWcm−2 at 650, 600, 550 and 500°C, respectively, using hydrogen as the fuel and stationary air as the oxidant. The total resistance of the cell was about 0.41, 0.51, 0.57 and 0.77Ωcm2, respectively. This encouraging data identifies PBCO as a potential cathode material for IT-SOFCs. [Copyright &y& Elsevier]

Abstract: The electrochemical performance of Pr0.7Sr0.3Co0.9Cu0.1O3−δ –xCe0.8Sm0.2O1.9 (PSCC–xSDC, x =0–40wt%) composite cathodes has been investigated for their potential utilization in intermediate-temperature solid oxide fuel cells (SOFCs). The results showed that the addition of SDC to PSCC improved remarkably the electrochemical performance of a PSCC cathode, and that a PSCC–35SDC cathode exhibited the best electrochemical performance in the PSCC–xSDC system. When SDC was used as the electrolyte, the interfacial resistance was smallest for 35wt% SDC, where the value was 0.137Ωcm2 at 700°C and 0.062Ωcm2 at 750°C, much lower than the corresponding interfacial resistance for pure PSCC. At 700°C, the cathodic overpotential of the PSCC–35SDC cathode in the SDC electrolyte was 70mV at a current density of 0.5Acm−2. This is a factor of two lower than that for a pure PSCC cathode (152mV at 700°C) under the same current conditions. The maximum power density of a single-cell using PSCC–35SDC as the cathode was 388 and 615mWcm−2 at 650 and 700°C, respectively. [Copyright &y& Elsevier]

Ceria based electrolyte materials have shown potential application in low temperature solid oxide fuel cells (LT-SOFCs). In this paper, Sm3+ and Nd3+ co-doped CeO2 (SNDC) and pure CeO2 are synthesized via glycine-nitrate process (GNP) and the electro-chemical properties of the nanocrystalline structure electrolyte are investigated using complementary techniques. The result shows that Sm3+ and Nd3+ have been successfully doped into CeO2 lattice, and has the same cubic fluorite structure before, and after, doping. Sm3+ and Nd3+ co-doped causes the lattice distortion of CeO2 and generates more oxygen vacancies, which results in high ionic conductivity. The fuel cells with the nanocrystalline structure SNDC and CeO2 electrolytes have exhibited excellent electrochemical performances. At 450, 500 and 550 °C, the fuel cell for SNDC can achieve an extraordinary peak power densities of 406.25, 634.38, and 1070.31 mW·cm−2, which is, on average, about 1.26 times higher than those (309.38, 562.50 and 804.69 mW·cm−2) for pure CeO2 electrolyte. The outstanding performance of SNDC cell is closely related to the high ionic conductivity of SNDC electrolyte. Moreover, the encouraging findings suggest that the SNDC can be as potential candidate in LT-SOFCs application. [ABSTRACT FROM AUTHOR]

Ca 3 Co 4 O 9-δ (Ca349) cathode is prepared by sol-gel method and its performance on new Sm 0.075 Nd 0.075 Ce 0.85 O 2-δ (SNDC) electrolyte was evaluated as cathode for intermediate temperature solid oxide fuel cells (IT-SOFC). The crystal structure and chemical compatibility with SNDC electrolyte are studied by X-ray diffraction (XRD). The micromorphology and electrochemical performance of Ca349 with SNDC electrolyte are characterized. The formation of Ca349 phase and good chemical compatibility between Ca349 and SNDC electrolyte are confirmed by XRD. The Ca349 cathode sintered at 850 °C for 5 h shows the best cathode performance, the area specific resistances (ASR) of Ca349 cathode are found to be 0.236 Ω cm 2 at 800 °C, and the ASR can be further decreased by incorporating SNDC electrolyte. The composite (Ca349-50 wt% SNDC) gives the lowest ASR values (0.093 Ω cm 2 at 800 °C). Its ASR is improved by at least 60% compare to single-phase Ca349 cathode. At 800 °C, the maximal power density of anode-supported SOFCs with Ca349 cathode reaches 410.09 mW cm −2 . The total resistance of the cell was only 0.168 Ω cm 2 . These encouraging data show that Ca349 onto SNDC with good electrochemical performance could be promising as a cathode material of IT-SOFC. [ABSTRACT FROM AUTHOR]

[Display omitted] • The semiconductor heterostructure 5BKFC-5SNDC electrolyte was designed and developed using BKFC and SNDC. • 5BKFC-5SNDC electrolyte possessed good electrolyte function with high ionic conductivity. • The electron transmission was blocked and the ion transferring was promoted through p-n heterostructure in the electrolyte. • Fuel cell with 5BKFC-5SNDC electrolyte achieved high power density of 911 mWcm−2 at 550° C. A semiconductor heterostructure material based on p-type cubic perovskite Ba 0.9 K 0.1 Fe 0.5 Co 0.5 O 3-δ (BKFC) and n-type fluorite Sm 0.075 Nd 0.075 Ce 0.85 O 2-δ (SNDC) forms micro p-n junctions in the low-temperature solid oxide fuel cells (LT-SOFCs) improving the electrochemical performance. A highly power density of 911 mW·cm−2 at 550° C was obtained with this material combination as electrolyte in a fuel cell, which is 20 % higher than that of the LT-SOFCs with pure BKFC as electrolyte. An ionic conductivity of 0.14 S·cm−1 at 550° C was achieved when equal amounts of BKFC and SNDC were employed as the electrolyte. Profound analysis of the heterostructure p-n junction shows that it blocks electron transport through mixed electronic and ionic conductor and enhances ionic transport improving the electrochemical performance of the fuel cell. The BKFC-SNDC composite electrolyte materials is a potential electrolyte material for raising the power density of fuel cells at lower temperatures. [ABSTRACT FROM AUTHOR]

Highlights • BaCo 0.7 Nb 0.2 Ta 0.1 O 3−δ (BCNT) cathode were prepared was prepared by solid phase reaction method. • The stability evaluation of the cathode showed the BCNT had sufficient stability during the operation. • Maximum power density of SDC electrolyte-supported cell reaches 626.41 mW·cm−2 at 800 °C. Abstract The BaCo 0.7 Nb 0.2 Ta 0.1 O 3−δ (BCNT) perovskite-type oxide was prepared by the conventional solid phase reaction method as a potential electrocatalyst for the oxygen reduction reaction. Its electrochemical properties were characterized. The results indicated that the BCNT oxide sintered at 1100 °C for 10 h had formed a single-phase cubic perovskite structure. And the BCNT–Sm 0.2 Ce 0.8 O 1.9 (SDC) mixture co-sintered at the same conditions showed good chemical compatibility and stability between BCNT and SDC. The BCNT cathode sintered at 1000 °C for 4 h on SDC electrolyte exhibited the lowest the polarization resistance (about 0.0495 Ω·cm2 at 800 °C). Moreover, with a 351 μm-thick SDC as electrolyte and BCNT as the cathode, maximum power densities of the single cell reached 466.81 and 626.41 mW·cm−2 at 750 and 800 °C, respectively, and the corresponding total interface polarization resistance of the cell were 0.0913 Ω·cm2 and 0.0552 Ω·cm2. Short-term stability of the cell showed that the cell was quite stable at 750 °C for 15 h. This suggested that BCNT was a very promising cathode material for IT-SOFCs. [ABSTRACT FROM AUTHOR]

• A novel CBP 0.4 C material is developed as a potential cathode of IT-SOFCs. • Doping with Pr ions can improve the electrochemical performance of the cathode. • Maximum power density of cell with CBP 0.4 C cathode reached 0.705 W/cm2 at 800 °C. The Ca 2.9−x Bi 0.1 Pr x Co 4 O 9−δ (CBP x C, x = 0–0.6) oxides were prepared by sol–gel method, as the potential cathode of anode-supported intermediate temperature solid oxide fuel cells (IT-SOFCs). The electrochemical performance test showed that the CBP x C oxide sintered at 700 °C for 10 h could form a single-phase crystal structure, and when the doping ratio of Pr ion was x = 0.4, the CBP x C cathode on the SDC electrolyte sintered at 950 °C for 5 h obtained the minimum interface polarization resistance (about 0.406 Ω·cm2 at 800 °C). Meanwhile, on the basis of the above conditions, we had fabricated Ni 0.95 Cu 0.05 O x -SDC/SDC/CBP 0.4 C single cell with the optimized CBP x C (x = 0.4) cathode, in which the SDC electrolyte thickness was 55.6 μm. The maximum power densities of the single cell reached 0.705 W/cm2 and 0.570 W/cm2 at 800 °C and 750 °C, the corresponding polarization resistances were 0.051 Ω·cm2 and 0.153 Ω·cm2, respectively. This suggested that CBP 0.4 C was a very promising cathode material for IT-SOFCs. [ABSTRACT FROM AUTHOR]

Abstract: The electrolyte materials Ce0.85Sm0.15O1.925–x at.% FeO1.5 (x =0, 0.5, 1, 2, 3) were synthesized by means of glycine–nitrate process (GNP). Their structures and ionic conductivities were characterized by X-ray diffraction, SEM and AC impedance spectroscopy. All the electrolytes were found to be ceria-based solid solutions of fluorite type structures. Grain size increased with increased Fe2O3 content up to 0.5at.% and then became almost constant with further addition of Fe2O3. The grain-boundary resistance could be significantly decreased by small addition of Fe2O3. Electrolyte-supported solid oxide fuel cells (SOFC) fabricated with Ce0.85Sm0.15O1.925–x at.% FeO1.5 (x =0.5, 3) electrolytes were studied and compared with the fuel cell with Ce0.85Sm0.15O1.925 as electrolyte. [Copyright &y& Elsevier]

Abstract: Ce0.85Sm0.15O1.925 samples have been prepared using the glycine-nitrate process. The effects of microstructure on their electrical properties were investigated by X-ray diffraction, density measurements, scanning electron microscopy and AC impedance spectroscopy. The grain-boundary conductivities and total conductivities increase with decreasing grain size for sintered densities of 95% or greater. The bulk conductivities are nearly independent of grain size for sintered densities of 95% or greater. It is found that the space-charge potential is nearly independent of grain size and the increase of the conduction path width is responsible for the increase of the apparent specific grain-boundary conductivity. The power densities and current densities of single cells based on Ce0.85Sm0.15O1.925 electrolytes with different grain size are evaluated. [Copyright &y& Elsevier]