This study presents a performance evaluation platform for sputtered thin-film electrodes used in biogas-driven, low-temperature solid oxide fuel cells (SOFCs). The design considerations include electrolyte material composition and thickness, anode material composition and thickness, anode fuel composition, and cathode composition and thickness, all derived from a review of existing literature. For the electrolyte, we propose a thickness of 100 μm for the main electrolyte made of gadolinium-doped ceria (GDC) and 0.1 μm for the auxiliary electrolyte made of scandia-stabilized zirconia. In terms of anode fabrication, we suggest a material composition of Ru/Ni-Cu-GDC, with thicknesses of 1 μm for Ni-Cu-GDC and a few nanometers for Ru in the nanoporous anode. For the anode fuel supply, we recommend mole ratios of 45% to 75% CH₄ and 25% to 55% CO₂ to assess the impact of biogas composition on power performance. Lastly, for the cathode, we propose a material composition of Pt-Ti-samarium-doped ceria with a thickness of 100 nm for the nanoporous structure.

Solid Oxide Fuel Cells (SOFCs) are energy conversion devices known for their significantly higher power density compared to other fuel cell types. However, their high operating temperatures pose challenges related to thermal stability. To address this, research is focusing on Low-Temperature SOFCs (LT-SOFCs), which function at lower temperatures and exhibit enhanced electrochemical performance. While various electrode materials are utilized in SOFCs, platinum (Pt) stands out for its excellent electronic conductivity and catalytic activity. Unfortunately, at the operating temperatures of SOFCs, Pt tends to agglomerate, leading to a rapid reduction in the triple phase boundary (TPB) and a subsequent decline in electrochemical reactions. In this study, LT-SOFCs were fabricated with a Praseodymium Oxide (PrOx) capping layer applied to a porous Pt cathode using sputtering, with various thicknesses achieved by adjusting the deposition time. The electrochemical performance of the LT-SOFCs was measured at 500^oC. Additionally, the degradation behavior of the LT-SOFCs was assessed by applying a constant voltage of 0.5 V for 48 hours. Scanning Electron Microscopy (SEM) analysis was also conducted on the PrOx capping layer thin films under the same operating conditions.

A yttria-stabilized zirconia (YSZ) cathode functional layer (CFL) was fabricated using a co-sputtering process to improve the oxygen reduction reaction (ORR) in solid oxide fuel cells (SOFCs). To optimize the yttria molar percentage and achieve a nano-granular structure with enhanced grain boundary density, the DC sputtering power for the metallic yttrium target was varied at 10, 30, and 50 W. Structural and compositional analyses were performed using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and X-ray diffraction (XRD). The results indicated that a DC power of 30 W resulted in a well-developed grain structure with high grain boundary density and an yttria composition close to the optimal molar percentage of 8-10 mol %. Under these optimized conditions, the SOFC with the co-sputtered YSZ CFL achieved a maximum power output of 9.22 mW/cm² at 450^oC, representing approximately a 43% enhancement compared to the reference cell. This highlights the significant potential of co-sputtering for future low-temperature SOFC applications.

Pinhole-free ionic conductors are critical to achieve optimal performance in thin film-solid oxide fuel cells (TF-SOFCs). However, nanoscale defects, especially pinholes, can induce current leakage and contribute to cell failure by creating electrical short circuits. This study introduced a novel methodology for detecting pinholes in yttria-stabilized zirconia (YSZ) thin-film solid oxide electrolytes. The approach utilized selective adsorption of silver (Ag) nanoparticles generated via a spark discharge generator (SDG). Analytical techniques, including focused ion beam (FIB), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), were employed to investigate interactions between Ag nanoparticles and nanoscale defects. Results showed that nanoparticle-based diagnostic methods were efficacious for defect characterization, offering a solution for enhancing the quality of thin-film electrolytes.

In this study, we successfully demonstrated a fuel cell fabrication method using a platinum-samarium-doped ceria (Pt-SDC) composite cathode, which could reduce the platinum content while maintaining the same thickness as the functional layer. The Pt-SDC composite cathode was deposited by a sputtering process in which two materials were simultaneously deposited by a co-sputtering system. Despite the decreased platinum content in the composite cathode, we achieved high performance of the fuel cell since Pt-SCD was able to form triple-phase boundaries (TPBs) not only at the interface between the cathode and the electrolyte but at the entire volumetric surface of the cathode. This composite cathode revealed that Pt-SDC could enhance the oxygen reduction reaction rate by enlarging the TPB site in the cathode. The fuel cell fabricated in this study with a composite cathode demonstrated improved performance at 1.66 times the peak power density of a pristine fuel cell.

In this study, we fabricated thin film solid oxide fuel cells on nanoporous anodic aluminum oxide (AAO) substrate for low-temperature operation using the all-through sputtering method. To deposit up to a three-micrometer thick anode with both porosity and electrical conductivity, we used the glancing angle deposition and co-sputtering methods. For the anode materials, we used nickel gadolinium-doped-ceria (Ni-GDC) mixed ionic and electronic conductor (MIEC), which improved hydrogen oxidation reaction reactivity at the anode side. TF-SOFCs were successfully operated at 500℃, and 223.6 mW/cm² was their highest measured maximum power density. We conducted structural and electrochemical analyses to figure out cells’ unique resistant characteristics; ohmic resistance through the anode thin film and polarization resistance of reaction area near the narrowed anode pores. We found how the anode thin film thickness affects the current collecting performance and the anode reactivity, and their effects were qualitatively and quantitatively compared.

Energy devices in modern society require high efficiency, carbon neutrality, and the capability of distributed power generation. A fuel cell is an energy conversion device, that satisfies all of these requirements. However, most fuel cells use hydrogen as a fuel, and more than half of hydrogen is currently produced through hydrocarbon reforming, resulting in significant energy loss. Additionally, the storage and supply of hydrogen require costly systems, and a large amount of energy is consumed during compression or liquidation processes. This paper develops a solid oxide fuel cell, that uses hydrocarbon directly as fuel to resolve this problem. A small amount of Ru is mixed with the Ni-based electrode, for the effective internal reforming of hydrocarbons. For rapid deposition of YSZ electrolytes, we developed a reactive sputtering process, using a DC power source. The developed thin-film solid oxide fuel cell, showed a performance of 76 mW/cm² at 500℃ using methane as fuel.

In this study, Yttria-stabilized zirconia (YSZ) functional layers were applied with different thin-film fabrication process such as sputtering and atomic layer deposition (ALD) to enhance oxygen reduction reaction (ORR) for solid oxide fuel cells. We confirmed that the YSZ functional layer deposited with sputtering showed relatively low grain boundary density, while the YSZ functional layer deposited with the ALD technique clearly indicated high grain boundary density through scanning electron microscopy (SEM) and X-ray diffractometry (XRD) results. The YSZ functional layer coated with the ALD technique revealed that more ORR kinetics can occur using high grain boundary density than the functional layer deposited with sputtering. The peak power density of the SOFC deposited with ALD YSZ indicates 2-folds enhancement than the pristine SOFC.

A high temperature sintering process for solid electrolyte is the main cause of the increase in manufacturing costs of SOFCs. In this study, we developed a novel flash light sintering technique as an alternative sintering process of the conventional thermal sintering process. The YSZ electrolyte films were fabricated by conventional screen-printing method and the flash light sintering process and ESB sintering aid were applied to improve the flash light sinterability of the YSZ electrolyte. In the flash light sintering process, the effect of various pulse conditions such as energy density, and pulse interval were investigated and the microstructure, crystallinity, and sintering behavior of the sintered films were analyzed to demonstrate the effectiveness of the flash light sintering process. The flash light sintered YSZ electrolyte layer was used to fabricate the anode-supported SOFCs and its functionality is successfully demonstrated with the high open circuit voltage. The significance of this study includes minimization of the process time from tens of hours to just a few seconds, thus facilitating the commercialization of SOFCs.

Solid oxide fuel cell is a next generation energy conversion device that can efficiently convert the chemical energy of fuel into electrical energy. Fuel flexibility is one of the advantages of SOFCs over other types of fuel cells. SOFCs can operate with hydrocarbon type fuel. While nickel based composite is commonly used in direct methane fueled SOFC anode because of its great catalytic activity for methane reforming, the direct use of hydrocarbon fuels with pure Ni anode is usually insufficient for facile anode kinetics, and also deactivates the anode activity because of carbon deposition upon prolonged operation. In this report, the Ni based anodes with 20 nm thick catalytic functional layers, i.e., Pt, Ru, and Pt-Ru alloy, are fabricated by using the co-sputtering method to enhance the anode activity and power density of direct-methane SOFC operating at 500℃.

The energy saving effect of reactant plasma in Atomic Layer Deposition (ALD) of ultrathin solid oxide fuel cell electrolyte was examined by measuring electrical current in real time. Actuating a plasma generator led to a remarkable change in electric current and therefore a Plasma Enhanced ALD (PE-ALD) Yttria-Stabilized Zirconia (YSZ) supercycle demanded ~12% higher process energy than a Thermal ALD (T-ALD) YSZ supercycle. Nonetheless, because PE-ALD YSZ electrolyte providing higher growth rate and higher gas tightness needed 2 times smaller cycle number compared to T-ALD YSZ electrolyte, applying oxygen plasma in ALD of YSZ electrolyte resultantly reduced total process energy by ~44%.