CeO2 and Nb2O5 modified Ni-YSZ anode for solid oxide fuel cell

Precise porosity control is highly desirable for improving the electrochemical performance of solid oxide fuel cells (SOFCs). Freeze casting is an established method for enabling high bulk porosity in structures and controlling pore orientation. In this study, freeze casting was used to fabricate tubular, anode-supported SOFCs with aligned and varying amounts of porosity by controlling the solids/water ratio in different casting slurries. SOFCs were prepared with a Ni/yttria and scandia stabilized zirconia (ScYSZ) anode support (AS), an anode functional layer (AFL), a ScYSZ electrolyte, a lanthanum strontium manganite (LSM)/ScYSZ cathode interlayer (CIL), and an LSM cathode. The permeability of the anode support was found to increase from 1.4 × 10−2 to 1.8 × 10−2 m2 as porosity was increased from 57 to 64 vol%, while the total cell resistance decreased by 35% from 0.93 to 0.60 Ohm cm2. When evaluated with 30 vol% H2 as the fuel at 800 °C, the decrease of concentration polarization enabled an increase in electrochemical performance by 42% from 0.35 to 0.50 W/cm2 as the porosity in the anode support was increased. Mechanical strength characterization using a three-point method showed there is a practical upper limit of the amount of porosity that can be designed into the anode support. This work paves a way for controlling porosity by freeze casting and understanding the correlation between porosity and concentration polarization losses in SOFCs.

Development and testing of anode-supported solid oxide fuel cells with slurry-coated electrolyte and cathode

Ni-Gd doped ceria (Ni-GDC) anodes exhibit high durability during direct butane utilization in solid oxide fuel cells (SOFCs). However, the cells containing Ni-GDC anodes showed less performance compared to those containing conventional Ni-Y stabilized zirconia (Ni-YSZ) anodes, when zirconia-ceria solid solution formed at the interface between the YSZ electrolyte and Ni-GDC anode during co-sintering at high temperature in anode-supported SOFCs. The formation of the solid solution increases electrochemical impedance at low frequencies due to oxygen nonstoichiometric variation process. To prevent the formation of this solution, La doped ceria (LDC) was infiltrated into the Ni-YSZ anode after sintering. The maximum power density of the cell containing Ni-YSZ anode with LDC infiltration (Ni-YSZ+LDC) was higher than those containing Ni-YSZ and Ni-GDC anodes. Distribution of relaxation times (DRT) analysis revealed that the polarization resistance of fuel oxidation process decreased, and the oxygen nonstoichiometric variation process was not observed after LDC infiltration. Power was continuously generated over 100 h using butane fuel for the Ni-YSZ+LDC. No carbon deposition was observed after the durability test, because the LDC nanoparticles enhanced the catalytic activity toward carbon oxidation. The LDC infiltration is an method to obtain the comparability of performance and durability for direct butane utilization.

In this chapter, the construction, principle of operation, types and production technologies of SOFCs are presented and characterized. Three main types of SOFC are described according to the type of support layer responsible for the mechanical strength of the cell: electrolyte-supported solid oxide fuel cells (ES-SOFC), anode-supported solid oxide fuel cells (AS-SOFC), and metal-supported solid oxide fuel cells (MS-SOFC). Base and raw materials for particular functional layers of solid oxide fuel cells are characterized, i.e., anode, electrolyte, and cathode layers. Thick- and thin-film technologies for the production of particular elements of SOFC fuel cells are presented. Using the example of technology developed in the Institute of Power Engineering Ceramic Department CEREL, the production technology of anode-supported solid oxide fuel cells and the method of characterizing the microstructure and electrochemical properties of the produced cells are presented.

A systematic study was initiated of anode-supported solid oxide fuel cells (SOFCs) with Nd2NiO4 cathodes. This type of cathode, a mixed conducting K2NiF4-type material, can be considered as a candidate for SOFC applications. In this study, the influence of (1) the presence of a Ce0.8Gd0.2O1.9 (CGO) interlayer between the electrolyte and the cathode, (2) sintering conditions, and (3) the grain size of the powder on the performance of SOFCs with Nd2NiO4 cathodes was investigated in more detail. Results from current density-voltage characteristics and permeation and gas diffusion measurements showed that the electrochemical performance was promising for SOFCs including a CGO interlayer and a Nd2NiO4 cathode (prepared with a powder with a d50 of 0.5A∕cm2 or 0.8μm) sintered at 1100°C or higher; current density at 800°C and 700mV between 1.2 and 1.3A∕cm2. The microstructure of the cathode was such that no gas diffusion problems occurred.

Microtubular anode-supported solid oxide fuel cells (μt-SOFC) were created with a metallic coil embedded in the anode to act as current collector. The electrochemical performance was experimentally examined by comparing the power density (PD) of μt-SOFC with embedded coils of different turns per unit length and composition (nickel and palladium). It is shown that an increase in the turns per unit length results in a proportional current density increase and in a quadratic increment of PD. Additional performance improvement is found for the cell with palladium current collector due to the higher catalytic activity for hydrogen oxidation.

Solid oxide fuel cell (SOFC) is well known as power and heat generation device which converts chemical energy directly from fuel into electricity. SOFC operate at high temperature becomes obstacle for SOFC which reducing ionic conductivity material of current electrolyte, reduce lifetime of cell components, high fabrication cost, limited durability and performance issues. This introduce to environment pollution and decrease the SOFC lifetime. The fabrication of durability and stability composite cathode are comprised from mixing of perovskite La0.6Sr0.4CO0.2Fe0.8 (LSCF) powders with nanoscale ionically conducting ceramic electrolyte materials, SDC-carbonate (SDCc) was overcome this problems. Powder preparation and composite cathode fabrication must consider which as main factors in the development of durability and stability of LSCF-SDCc composite cathode. Powders must in nanoscale to enhance the conductivity and decrease the interfacial polarization resistance and the composite cathode should in nanoporous morphology for achieve high power density over than 500 h and remarkable durability. Calcination also plays in important role and its operations will effects to the SOFC durability and performance. The necessary to prolong the lifetime and increase the SOFC performance has lead to development of durability and stability of SOFC. This paper reviews the durability and stability of the composite cathode and focus on the challenges in material technology.

The anode-supported solid oxide fuel cells (SOFCs) with an yttria-stabilized zirconia (YSZ) electrolyte have been successfully prepared by the sequential steps of fabricating technique including tape casting, spin coating, and screen-printing. Two types of the SOFCs are manufactured and their cell performances are characterized via the detail analysis of the electrochemical impedance spectroscopy (EIS). The maximum power densities are 411 and for the high and low performance cells at , respectively. According to the EIS analysis, the electrochemical performance of the poor cell is dominated by the anodic non-charge-transfer resistance, which is mainly resulted by the gas diffusion polarization due to the low porosity of the anode. The high performance cell is controlled by the simultaneous contributions of the ohmic resistance , the anodic polarization , and the cathodic polarization at the operation temperature of . However, the will dominate the performance of the cell as the temperature is lowered down to .

Solid oxide fuel cells (SOFCs), as highly efficient energy conversion devices, are anticipated to play a significant role in the realization of a low-carbon society. ENE-FARM type S (EF), equipped with SOFC stack, has been commercialized since 2012 by Osaka Gas. To further expand the market of EF, higher electrical efficiency, higher durability, lower cost of SOFC stack, and downsizing of EF are needed. For realizing these issues, two model changes were conducted in 2016 and 2020. The SOFC stack installed in the current EF, which is composed of Anode-supported SOFC (ASC), has established durability of over 12 years. For further widespread adoption in the EF market, we have focused on Metal-supported SOFCs (MSC), which have the potential to reduce costs by using fewer expensive ceramics.However, the use of a metal substrate in MSCs introduces unknown degradation phenomena that differ from those in ASCs. These phenomena include the degradation of the metal substrate and the interfacial reaction between the metal substrate and anode due to interdiffusion from the metal substrate and anode. Understanding and addressing the degradation phenomena originating from a metal substrate are significant challenges for the commercialization of MSCs. In this study, we investigated the degradation phenomena of MSCs, especially at the metal substrate/anode interface.The degradation phenomena are influenced by evaluation conditions such as durability time, temperature, and gas composition. The concentration of water vapor at the fuel gas outlet is much higher than at the fuel gas inlet throughout electrochemical reactions. To confirm the differences in the degradation phenomena due to gas composition, two MSC pieces were prepared. MSCs were fabricated at a lower temperature compared to ASCs, utilizing ceramic electrodes and electrolytes on a 16 cm2 ferritic stainless-steel substrate. Single cell tests were conducted using air at the cathode and fuel at the anode. The operating conditions for the evaluation were as follows: current density was varied from 0 to 0.42 A/cm², with H₂/H₂O used as the anode gas at two different dew points (DP). Test 1 was conducted at a DP of 30°C, and Test 2 was conducted at a DP of 88°C, while air served as the cathode gas. Both the anode gas and air flow rates were fixed during the evaluation. The operation was conducted with a fuel utilization factor (Uf) of approximately 10% and an air utilization factor (Ua) of approximately 20% at 0.42 A/cm².Figure 1 shows the results of the durability tests of 16 cm2-MSC cells conducted at 800°C. The change in voltage from the initial value is denoted as ΔV. The reduction in voltage on the fuel outlet side was approximately 25 mV greater than that on the fuel inlet side after 1000 hours. During these durability tests, the IR and electrode overvoltage (η) were measured by the current interruption method. The open circuit voltage remained stable without significant changes throughout the 1000 hours durability tests for both the fuel inlet and outlet sides. Figure 2 shows the results of IR and η during the durability tests conducted at 800°C. The observed reduction in voltage was attributed to increases in both IR and η, with similar increments noted for both the fuel inlet and outlet sides in relation to IR. It was found that no abnormally high resistance layer formation or significant increase in oxidation layer occurred on the outlet side after 1000 hours at 800°C.The more pronounced voltage drop observed at the outlet side is primarily due to a more significant increase in η. Considering that the evaluation was conducted under uniform conditions, except for the water vapor concentration on the anode gas side, it is plausible that the factors contributing to the increase in η are associated with the sintering or poisoning of the anode. These findings suggest that the reduction in reaction area and decreased gas diffusivity are significant contributors to the observed effects. In the presentation, we will discuss the insights derived from the electrochemical measurement results along with detailed cross-sectional analyses conducted after the durability tests. Figure 1

Direct internal reforming (DIR) operation provides many benefits for solid oxide fuel cells (SOFCs) by eliminating the need for an extra reformer. Anode-supported SOFCs (AS-SOFCs) are commonly used for DIR operations. However, the strong endothermic reforming reactions at the cell entrance may result in large thermal stresses and lead to premature failure. In this study, a two-dimensional model was developed to analyze the differences between the AS-SOFC and the new generation metal-supported SOFC (MS-SOFC) in DIR operations. The model considered the coupling effects of the chemical/electrochemical reactions, the mass/charge/heat transport processes and the thermal mechanical stress. The distributions of temperature, species composition, current density and thermal stress were determined and compared for both structures. The failure probability of the cell was estimated by stress distributions. The results showed that the MS-SOFC led to a gentler temperature distribution and a smaller failure probability with slight performance increase compared to the AS-SOFC.

YSZ ( yttria-stabilized zirconia)-modified LSM composite cathodes were fabricated by formation of YSZ film on triple phase boundary (TPB) of LSM/YSZ/gas. The YSZ coating film greatly enlarged electrochemical reaction sites from the increase of additional TPB. The composite cathode was formed on thin YSZ electrolyte (about 30 Um thickness) supported on an anode and then I-V characterization and AC impedance analyses were performed at temperature between . As results of the impedance analysis on the cell at with humidified hydrogen as the fuel and air as the oxidant, R1 around the frequency of 1000 Hz represents the anode Polarization. R2 around the frequency of 100Hz indicates the cathode polarization, and R3 below the frequency of 10 Hz is the resistance of gas phase diffusion through the anode. The cell with the composite cathode produced power density of at air and oxygen atmosphere, respectively. The I-V curve could be divided into two parts showing distinctive behavior. At low current density region (part I) the performance decreased steeply and at high current density region (part II) the performance decreased gradually. At the part I the performance decrease was especially resulted from the large cathode polarization, while at the part H the performance decrease related to the electrolyte polarization.

Microstructure and polarization characteristics of anode supported tubular solid oxide fuel cell with co-precipitated and mechanically mixed Ni-YSZ anodes

Investigation of LSM/8YSZ cathode within an all-ceramic SOFC, Part II: Optimization of performance and co-sinterability

Solid oxide fuel cells for stationary, mobile, and military applications

Three-dimensional computational fluid dynamics modeling of anode-supported planar SOFC