SOFC Electrolyte Research Articles

ANALISIS PENGARUH KONDUKTIVITAS IONIK MATERIAL ELEKTROLIT PADA KINERJA SOLID OXIDE FUEL CELL

SOFC electrolytes are known for their ohmic resistance aspect, which is dependent on temperature. Using COMSOL Multiphysics numerical simulation, analysis of SOFC power performance with yttria-stabilized zirconia (YSZ) and lithium sodium carbonate – gadolinium-doped ceria ((LiNa)2CO3-GDC) electrolytes was conducted to inspect the performance of these electrolytes in their application in SOFC. The ionic conductivity of YSZ was differentiated based on the mole value of the yttria content, namely 8, 8.95, 10 and 11.54 mol. Meanwhile, GDC varied based on the (LiNa)2CO3 content such as 7.8, 10, 16.8 and 30 %. With the numerical model, the calculation error is an average of 7.32 % and 6.89 % for the experimental power and voltage values. In SOFC with the YSZ electrolyte, it was found that the power output can increase 26.4–35 times with an increase in operating temperature from 500 °C to 750 °C. Whereas in SOFC with the GDC electrolyte, it was found that the power output can increase 18.6–22.6 times with an increase in operating temperature from 500 °C to 750 °C. YSZ also showed the potential for an increase in power output as the SOFC temperature increases above 750 °C, while the 30 % variation (LiNa)2CO3-GDC shows a limited increase in ionic conductivity at 750 °C.

Investigating the microstructural and electrochemical performance of novel La0.3Ba0.7Zr0.5X0.3Y0.2 (X = Gd, Mn, Ce) electrolytes at intermediate temperature SOFCs

La0.3Ba0.7Zr0.5X0.3Y0.2 (X = Gd, Mn, Ce named as LaBaZrGdY, LaBaZrMnY, and LaBaZrCeY, respectively) SOFC electrolytes were prepared via novel organic and chemical auto-combustion methods, via spinach extract and oxalic acid as chelating agents.

Zirconia-based materials in alternative energy devices - A strategy for improving material properties by optimizing the characteristics of initial powders

This work is devoted to the demonstration of a real multifunctional material – zirconia based nanopowders, which can be used in the manufacture of various types of devices that convert natural energy sources into electricity (electrolyte and anode for SOFC, moisture-to-electricity converter). It was shown that such characteristics of nanopowders as particle size, specific surface area, and type of surface centers, which depend on the temperature of nanopowder synthesis, could play both a positive and a negative role in the formation of the functional properties of a device. It was found that the synthesis of 8YSZ nanopowders at 700 °C is optimal for the manufacture of a dense electrolyte material and a porous SOFC anode material during sintering at 1400–1450 °C. The addition of a small amount of Al2O3 at the synthesis stage accelerates the sintering of the SOFC electrolyte material by 120 °C and leads to increasing the density to 97% of the theoretical value. The strength of the sintered anode material practically does not change after reduction in an atmosphere of N2–10% H2–5% CO2 and the value is 100 MPa.The synthesis temperature of 8YSZ nanopowder at 700 °C is also optimal for the manufacture of porous converters of ambient humidity into electricity. The formation of particles with a given size and type of surface centers allows generating an electric potential (100–200 mV) for hundreds of hours, which is 2–3 times higher than that of larger and smaller powders. The result of the work show that there are optimal conditions for the synthesis of powders (synthesis method, additives, synthesis temperature), as a result of which nanopowders are formed with characteristics (particle size, specific surface area, morphology) necessary and sufficient for the manufacture of several types of materials for devices of alternative energy.

Electrical Conductivity and Dielectric Properties of Zirconia-Based SOFC Electrolytes Processed by Microwave and Conventional Sintering

Electrical Conductivity and Dielectric Properties of Zirconia-Based SOFC Electrolytes Processed by Microwave and Conventional Sintering

Enigmatic structure–property behaviour in SOFC and SOEC electrolyte materials

Enigmatic structure–property behaviour in SOFC and SOEC electrolyte materials

Aqueous Thick-Film Ceramic Processing of Planar Solid Oxide Fuel Cells Using La0.20Sr0.25Ca0.45TiO3 Anode Supports

Recent research into the upscaling and implementation of Rh/Ce0.80Gd0.20O1.90 co-impregnated La0.20Sr0.25Ca0.45TiO3 (LSCTA-) anodes in electrolyte-supported SOFC at short-stack industrial scales has resulted in extremely robust performance under realistic operation and tolerance to harsh conditions. Furthermore, evaluation of the mechanical strength of LSCTA- and incorporation of this material into anode-supported SOFC also yielded promising performance at the button cell scale (using Ni and CeO2 catalyst impregnates). The knowledge on ceramic processing obtained during these previous research campaigns may be used to develop anode-supported SOFC with LSCTA- ‘backbones’ that have been optimised for high mechanical strength, high ‘effective’ electronic conductivity and sufficient porosity. Therefore, this manuscript details the preparation of anode-supported SOFC using the thick-film ceramic processing technique of aqueous tape casting, the optimisation of anode microstructure through addition of aqueous solvent-compatible graphitic and methacrylate polymer pore formers and the co-sintering of a LSCTA- support with a typical SOFC electrolyte material.

Synthesis of Borate Doped La10Ge6O27: Confirming the Presence of a Secondary Conducting Pathway

The investigation of oxide ion conductivity in apatite germanates has attracted significant interest due to potential applications in SOFC electrolyte materials. These systems conduct via interstitial oxide ions, and a range of studies have indicated the importance of the GeO4 units in the conduction process. In this paper, we investigate the effect of boron incorporation on the structure and conductivity. Studies show that heat treatment of La10Ge6O27 with H3BO3 leads to an expansion in cell volume, attributed to incorporation of borate groups in the oxygen ion channels within the structure. For low levels of dopant i.e La10Ge6O27(BO1.5)0.5, a small enhancement in conductivity was observed attributed to a transition from a triclinic to a hexagonal apatite. For further increases in boron content, the conductivity was shown to decrease attributed to the blocking of the conduction pathway down the apatite channels. Interestingly, significant oxide ion conductivity was still observed, which provides the first experimental support for a secondary conduction mechanism perpendicular to the apatite channels proposed by prior modelling studies.

On the ionic conductivity of some zirconia-derived high-entropy oxides

The reported High Entropy Oxides (HEOs) up to now exhibit lower ionic conductivity values than those of classical SOFC electrolytes. Multi-cations oxides, stabilized with the fluorite-type structure are investigated here in order to examine whether the high entropy is relevant to enhance the anionic conductivity of such HEOs, or not. The two synthesis routes that are used do not show significant impact on material properties. Based on configurational entropy (≥ 1.5 kB/f.u. for HEOs) and ionic radius difference calculations, new compositions are designed and prepared: i) the (Hf1/3Ce1/3Zr1/3)1-x(Gd1/2Y1/2)xO2-x/2 series in which the x ratio is increased so as to promote a high vacancy concentration, ii) the (HfxCeyZr1-x-y)0.85Yb0.15O1.93 series based on the critical radius concept. The ionic conductivity of these HEOs is slightly improved compared to previously reported data but does not exceed 4 × 10−4 S.cm−1 at 600 °C. Possible causes of such a low ionic conductivity value are discussed.

Highly enhanced electrical properties of lanthanum-silicate-oxide-based SOFC electrolytes with co-doped tin and bismuth in La9.33−xBixSi6−ySnyO26

Solid oxide fuel cells (SOFCs) are one of the most promising clean energy sources to be developed. However, the operating temperature of SOFCs is currently still very high, ranging between 1073 and 1273 K. Reducing the operating temperature of SOFCs to intermediate temperatures in between 773 and 1073 K without decreasing the conductivity value is a challenging research topic and has received much attention from researchers. The electrolyte is one of the components in SOFCs which has an important role in reducing the operating temperature of the SOFC compared to the other two fuel cell components, namely the anode and cathode. Therefore, an electrolyte that has high conductivity at moderate operating temperature is needed to obtain SOFC with medium operating temperature as well. La9.33Si6O26 (LSO) is a potential electrolyte that has high conductivity at moderate operating temperatures when this material is modified by doping with metal ions. Here, we report a modification of the structure of the LSO by partial substitution of La with Bi3+ ions and Si with Sn4+, which forms La9.33−xBixSi6−ySnyO26 with x = 0.5, 1.0, 1.5, and y = 0.1, 0.3, 0.5, in order to obtain an electrolyte of LSO with high conductivity at moderate operating temperatures. The addition of Bi and Sn as dopants has increased the conductivity of the LSO. Our work indicated highly enhanced electrical properties of La7.83Bi1.5Si5.7Sn0.3O26 at 873 K (1.84 × 10−2 S cm−1) with considerably low activation energy (Ea) of 0.80 eV comparing to pristine La9.33Si6O26 (0.08 × 10−2 S cm−1).

Tailoring of properties in the preparation level of nano crystalline Ce0.8Sm0.2O1.9-δ(SDC) for the use of SOFC electrolyte

Ce0.8Sm0.2O1.9-δ (SDC) has been a potential candidate for SOFC electrolyte for its compatibility with other cell components such as with Lanthanum ferrite based electrodes. Crystalline Ce0.8Sm0.2O1.9-δ (SDC) has been synthesized by a novel combustion route. A fuel rich configuration of the precursors favours the formation of agglomerate free fine particles. The XRD pattern of the powder has been observed as a function of calcination temperature. As synthesis powder has been observed phase pure except with traces of residual carbon impurities as has been observed from the FTIR pattern. The purity of the as synthesized powder has been attributed to the optimized value of elemental stoichiometric coefficient, which in turn has been attributed to the supplement of optimized thermal energy to the precursor gel. The crystallite size has been calculated and compared for the different calcination temperatures which as expected, has enhanced with the calcinations temperature. The chemical reactivity with LSCF cathode material tested under XRD reveals no reactive phase formed in the operating temperature range. The FESEM image of the powder reveals the fineness of the powder and its homogeneity. Circular discs have been pressed and sintered for densification. Density above 96% was observed from the measurement. The SEM of the sintered pellet has been checked for phase purity and pure crystalline XRD peaks confirmed the crystalline character. The sintering temperature 1450 °C has been observed to be one of the lowest of the reported values. It was attributed to the fine powder with high surface area.The study facilitates a combustion synthesis of ceramic oxide powder in general and of SDC in particular at comparatively low temperatures such as those 550 °C or even lower.

Characterization of SrFe0.9‐xCuxMo0.1O3‐δ (x = 0, 0.1 and 0.2) as cathode for intermediate‐temperature solid oxide fuel cells

SummaryCu doped perovskites SrFe0.9‐xCuxMo0.1O3‐δ (SFCM, x = 0‐0.2) are explored as cathodes for IT‐SOFCs. The influence of Cu doping on the property of SFCM series was studied in detail. The oxygen content decreases with the increase of Cu doping amount. SFCM samples are chemically compatible with LSGM electrolyte. However, the TEC values are still a bit higher than that of some common SOFC electrolytes. At 750°C, the Rp values are 0.261, 0.227 and 0.155 Ω·cm2 for SFCM0, SFCM0.1, and SFCM0.2. The obtained activation energies for x = 0, 0.1, and 0.2 are 1.01, 0.98, and 0.87 eV, respectively. These results indicate that Cu doping into SrFe0.9‐xCuxMo0.1O3‐δ has a favorable effect on the electrochemical activity of the materials.

Crystal defects and phase transitions of nanocrystalline yttria-stabilised zirconia induced by high-energy ball milling

Yttria-stabilised zirconia (YSZ) is a promising electrolyte for SOFCs and gas sensors. In this study, the particle size of a co-precipitated 5 mol% yttria-stabilised zirconia (5 YSZ) powder was refined from 10.47 μm to 130 nm via high-energy ball milling to improve its sinterability and ionic conductivity. The ball milling process increased the specific surface area of the 5 YSZ powder from approximately 11 to 22 m2 g−1. The transmission electron microscopy (TEM) and high-resolution TEM (HRTEM) results indicated that the 5 YSZ crystallites decomposed into irregular shapes with the evolution of point, linear, and planar defects. An increase in the milling duration increased the number of oxygen defects in the 5 YSZ powder, as revealed by the X-ray photoelectron spectroscopy results. The tetragonal-to-monoclinic phase transformation occurring in the powder was investigated by X-ray diffraction, Raman spectroscopy, HRTEM, and selected-area electron diffraction pattern analyses. The ball-milled powders could be easily densified, but the presence of too many crystal defects and the large fraction of the m-ZrO2 phase were detrimental to the further densification of the 5 YSZ powders. In spite of the high sintering temperature (1500 °C) used in this study, the maximum relative density of 99.67% could be achieved for the powder ball-milled for 60 min at the rotor speed of 1500 rpm. Moreover, the ionic conductivity of 5 YSZ was improved significantly from 20.6 to 36.2 mS cm−1 (850 °C) after the high-energy ball milling process.

Electrical properties of Ni-doped Sm2O3 electrolyte

Nowadays, semiconductor ionic materials have drawn significant attention for developing new electrolytes in low temperature solid oxide fuel cells (LT-SOFCs). Here we investigate the effect of nickel doping on ionic conductivity of Sm2O3 as an electrolyte material for low temperature SOFCs. The amount of Ni ion doping has an intense effect on the electrochemical properties and power generation. An optimized composition of 10 mol% nickel doped samarium oxide (10NSO) as an electrolyte in the fuel cell has a high open circuit voltage (OCV) of 1.09 V and a notable power output of 1080 mW cm−2 at 520 °C. Further investigation revealed that the 10NSO displays a superior ionic conduction up to 0.26 S cm−1 at 520 °C. Moreover, the cell demonstrates high stability up to 80 h. The high electrochemical property and good stability recommend that the NSO is a favorable candidate for symmetrical SOFC electrolyte.

Structural and ionic conductivity of Cu-doped titania (Ti0.95Cu0.05O2−δ) for high temperature energy devices

The Cu-doped titania (Ti0.95Cu0.05O2-δ) is studied here as a solid-state ionic conductor for its possible application in high temperature energy devices such as an electrolyte for SOFC. The sample in the powder form was obtained by solid state method using TiO2 and copper acetate by heating up to 1200 °C for 10 h. It was characterized by XRD, FT-IR, Raman, SEM/EDS, DRS-UV-Visible, photoluminescence, BET and ac-impedance techniques. The oxide ion conductivity (σt) values obtained from ac-impedance measurements showed a linear increase with temperature from 300 − 700 °C. The σt values are similar to that of Ln-doped ceria, and the highest conductivity of 1.41 × 10−4 Scm−1 was recorded at 700°C. The activation energy for total conductivity was found to be 0.82 eV. The ionic and electronic transport numbers are 0.79 and 0.21, respectively. This study suggests the plausible use of rutile TiO2 based (low-cost and structurally stable) materials as electrolytes in SOFC.

Facile Preparation of Cu2+-doped Tin(IV) Pyrophosphate /Potassium Metaphosphate Composite as a Highly Efficient Electrolyte for Intermediate Temperature SOFCs

Facile Preparation of Cu2+-doped Tin(IV) Pyrophosphate /Potassium Metaphosphate Composite as a Highly Efficient Electrolyte for Intermediate Temperature SOFCs

Structural, optical and enhanced electrical properties of vanadium alloyed sodium bismuth titanate solid solution synthesized by a chemical-mechanical hybrid method

This work focuses on the effect of V2O5 addition on the structural, optical and electrical properties of Sodium Bismuth Titanate (Na0.5Bi0.5TiO3) nanomaterials, for its possible application as an electrolyte in SOFC. Pure Na0.5Bi0.5TiO3 (NBT) material has been synthesized using citrate auto-ignition method and V2O5 has been reinforced in the perovskite structure by mechanical alloying. X-ray diffraction analysis confirms the formation of the rhombohedral phase of NBT perovskite with space group R3c. Rietveld Analysis indicates the presence of insoluble minor V2O5 phase in the 20% milled composition. The values of lattice parameters, particle size, and the microstrain have been found to vary with V2O5 addition. The presence of different bonds has been confirmed from FT-IR analysis. It has been found that the vanadium incorporation can tune the optical bandgap of the material. The real part of complex ac conductivity has been found to follow universal Jonscher power law. The variation in conductivity is correlated with the structural changes due to V2O5 addition. The highest conductivity achieved was 1.0143 × 10−4 at 400 °C for the 15% doped composition. The conductivity mechanism has been explained by Mott’s variable range hopping model.

Effect of Li2CO3 and LiOH on the ionic conductivity of BaCe0.9Y0.1O3 electrolyte in SOFCs with a lithium compound electrode

The effects of Li2CO3 and LiOH on the ionic conductivity of BaCe0.9Y0.1O3(BCY)-x%Li2CO3 (x = 0, 5, 10 and 30) and BCY-y%LiOH (y = 0, 2, 5 and 8) composite electrolytes were investigated. Symmetrical cells with the structure of foam Ni–Ni0.8Co0.15Al0.05LiO2 (NCAL)∖BCY-x%Li2CO3 or y%LiOH∖foam Ni-NCAL and Pt∖BCY-x%Li2CO3 or y%LiOH∖Pt were prepared with NCAL-coated foam Ni and porous Pt as symmetrical electrodes, respectively. The ionic conductivity test results of the cells with Pt as the symmetrical electrode showed that the addition of LiOH did not improve the ionic conductivity of the BCY electrolyte, while the addition of Li2CO3 could significantly improve the ionic conductivity of the BCY electrolyte. The maximum power density of the cells with the structure of foam Ni-NCAL∖BCY-x%Li2CO3 or y%LiOH∖foam Ni-NCAL decreases with the increase in the amount of Li2CO3 or LiOH, which indicates that adding Li2CO3 or LiOH to BCY via mechanical mixing did not improve the electrochemical performance of the cells with NCAL as the electrode, and the NCAL electrode has the greatest impact on the performance of the cells. The interface of Li2CO3 and BCY should be a high-speed channel for ion conduction. Increasing the effective area of the interface between BCY and Li2CO3 and optimizing its continuity in the electrolyte should be the main development direction for improving the ionic conductivity.

High ionic conductivity dysprosium and tantalum Co-doped bismuth oxide electrolyte for low-temperature SOFCs

A novel double dysprosium- and tantalum-doped bismuth oxide electrolyte synthesized by solid-state reaction for low-temperature solid oxide fuel cells (LT-SOFCs) is here reported. The phase structures at room temperature were defined by X-ray powder diffraction (XRD). A stable δ-Bi2O3 phase was obtained by co-doping Bi2O3 with Dy2O3 and Ta2O5 in specific contents. The effect of the co-dopant total content (5–15 mol%) on the ionic conductivity was measured as a function of temperature (300 to 700 °C). Results revealed that the (Dy2O3)13(Ta2O5)2(Bi2O3)85 system showed the highest ionic conductivity as 0.08 S cm−1 at 500 °C, which is three times higher than the binary system reported in the literature (E2O3)20(Bi2O3)80 (20ESB) and in the same range as the ternary system with the highest conductivity reported so far (Dy2O3)8(W2O3)4(Bi2O3)88 (8D4WSB). The lowest activation energy for our system was 0.20 eV at temperatures higher than 550 °C.

Interfacial Properties of Bilayer SOFC Electrolytes Via Scale Bridging Simulations

There has been significant interest in the bilayer materials used as Solid Oxide Fuel Cell Oxides (SOFCs) electrolytes. Multiple studies have explored the two participating materials in bilayer electrolytes, individually. However, the interfaces formed by them remain largely unexplored due to their complex nature. In order to advance the fundamental science of bilayer electrolytes, in this work a multiscale modeling study of the interface formed in commonly used SOFC electrolyte- ‘Ceria (CeO2)/yttria-stabilized zirconia (YSZ)’, was conducted. First, a realistic YSZ/CeO2 interface model containing all the important microstructural features of the interface such as dislocations, point defects, and lattice strains was prepared by using classical molecular dynamics (MD) simulations. Then, density functional theory was implemented to analyze the electronic properties of the realistic YSZ/CeO2 interface model prepared by MD. It was found that, at the interface, the overall strain in CeO2 and YSZ is compressive and tensile, respectively, as expected; however, the local strain at the core of the dislocation is converse. At dislocations, CeO2 was found to have tensile strain whereas YSZ has compressive strain. The presence of tensile strain in CeO2 at the core of the dislocations might contribute to the formation of O vacancies and reduction of Ce4+ to Ce3+, as observed in experiments. Overall, this work for the first time integrates the classical and quantum simulations to prepare and analyze a realistic working-class YSZ/CeO2 interface, resulting in the long-sought explanation for the experimentally observed Ce reduction at the YSZ/CeO2 interface.1 Acknowledgments This work was supported in part by the International Institute for Carbon-Neutral Energy Research (I2CNER) sponsored by the World Premier International Research Center Initiative (WPI) and the JSPS Core-to-Core Program, A. Advanced Research Networks and Paul Scherrer Institut. The computations were performed by using Computational Science Research Center, Okazaki, Japan, and the HPC supercomputers at I2CNER, Kyushu University, Japan.

Mechanism for Major Improvement in SOFC Electrolyte Conductivity When Using Lithium Compounds as Anode

Recent studies indicate that the electrolyte ionic conductivity in an SOFC can be considerably increased by using lithium compounds as the electrode. We found that the ionic conductivity of Gd0.1Ce...