Publications by authors named "Rak Hyun Song"

The present work aims to predict the degradation in the performance of a solid oxide fuel cell (SOFC) cathode owing to cation interdiffusion between the electrolyte and cathode and surface segregation. Cation migration in the (LaSr)CoFeO (LSCF)-GdCeO (GDC) composite cathode is evaluated in relation to time up to 1000 h using scanning transmission electron microscopy (STEM)-energy-dispersive X-ray spectroscopy (EDXS). The resulting insulating phase formed within the GDC interlayer is quantified by means of the volume fraction using a two-dimensional (2D) image analysis technique.

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Solid oxide fuel cells (SOFCs) are highly efficient, low-emission, and fuel-flexible energy conversion devices. However, their commercialization has lagged due to the lack of long-term durability. Among several performance degradation mechanisms, cathode degradation and elemental inter-diffusion of the electrolyte and cathode has been identified as the predominant factors.

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Since the high configurational entropy-driven structural stability of multicomponent oxide system was proposed Rost in 2015, many experiments and simulations have been done to develop new multicomponent oxides. Although many notable findings have shown unique physical and chemical properties, high configurational entropy oxide systems that have more than 3 distinct cation sites are yet to be developed. By utilizing atomic-scale direct imaging with scanning transmission electron microscopy and AC-impedance spectroscopy analysis, we demonstrated for the first time that a multicomponent equimolar proton-conducting quadruple hexagonal perovskite-related BaREAlZrO (RE = rare earth elements) oxide system can be synthesized even when adding eight different rare earth elements.

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Cr poisoning of cathode materials is one of the main degradation issues hampering the operation of solid oxide fuel cells (SOFCs). To overcome this shortcoming, LaNiFeO (LNF) has been developed as an alternative cathode material owing to its superior chemical stability in Cr environments. In this study, we develop a hybrid electrochemical deposition technique to fabricate a nanostructured LNF-gadolinium-doped ceria (GDC) (n-LNF-GDC) cathode with enhanced active reaction sites for the oxygen reduction reaction.

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Solid-state perovskite solar cells have been expeditiously developed since the past few years. However, there are a number of open questions and issues related to the perovskite devices, such as their long-term ambient stability and hysteresis in current density-voltage curves. We developed highly efficient and hysteresis-less perovskite devices by changing the frequently used TiO mesoscopic layer with polymer-hybridized multidoped ZnO nanocrystals in a common n-i-p structure for the first time.

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State-of-the-art cathodes for solid oxide fuel cells (SOFCs), such as (La,Sr)MnO -(Y O ) (ZrO ) (LSM-YSZ), suffer from sluggish oxygen reduction reaction (ORR) kinetics at reduced temperatures, leading to a significant decline in their performance. Herein, we report a tailored SOFC cathode with high ORR activity at intermediate temperatures using a simple but effective approach based on "electrochemical" surface modification. The proposed process involves chemically assisted electrodeposition (CAED) of a metal hydroxide (LaCo(OH) ) on LSM-YSZ surfaces followed by in situ thermal conversion of LaCo(OH) to perovskite-type LaCoO (LCO) nanoparticles during the SOFC startup.

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An anode-supported flat-tubular solid oxide fuel cell is an advanced cell design, which offers many advantages including a high volumetric power density, a minimized sealing area and a high resistance to thermal cycling. Infiltration of nano-sized noble metal catalysts into a porous cathode is known to be an effective method to improve cathode performances at reduced temperatures, but the cathode stability is of potential concern. This study addresses the performance and durability of anode-supported flat-tubular solid oxide fuel cells with Ag-infiltrated cathodes.

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Carbon-free cobalt oxide cathodes for lithium-oxygen batteries are fabricated via an electrodeposition-conversion process. The Co3O4-only cathodes show a remarkably reduced voltage gap (by ca. 550 mV compared to the carbon-only cathode) as well as excellent long-term cyclability.

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