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Nanomaterials for Advanced Electrode of Low Temperature Solid Oxide Fuel Cells (SOFCs)
Ishihara, Tatsumi The Korean Ceramic Society 2016 한국세라믹학회지 Vol.53 No.5
The application of nanomaterials for electrodes of intermediate temperature solid oxide fuel cells (SOFC) is introduced. In conventional SOFCs, the operating temperature is higher than 1073 K, and so application of nanomaterials is not suitable because of the high degradation rate that results from sintering, aggregation, or reactions. However, by allowing a decrease of the operating temperature, nanomaterials are attracting much interest. In this review, nanocomposite films with columnar morphology, called double columnar or vertically aligned nanocomposites and prepared by pulsed laser ablation method, are introduced. For anodes, metal nano particles prepared by exsolution from perovskite lattice are also applied. By using dissolution and exsolution into and from the perovskite matrix, performed by changing $P_{O2}$ in the gas phase at each interval, recovery of the power density can be achieved by keeping the metal particle size small. Therefore, it is expected that the application of nanomaterials will become more popular in future SOFC development.
Preparation of LaGaO3 Based Oxide Thin Film on Porous Ni-Fe Metal Substrate and its SOFC Application
주용완,Hiroshige Matsumoto,Tatsumi Ishihara,Toru Inagaki,Hiroyuki Eto 한국세라믹학회 2008 한국세라믹학회지 Vol.45 No.12
LaGaO3 thin film was prepared on Ni-Fe metal porous substrate by Pulsed Laser Deposition method. By the thermal reduction, the dense NiO-Fe3O4 substrate is changed to a porous Ni-Fe metal substrate. The volumetric shrinkage and porosity of the substrate are controlled by the reduction temperature. It was found that a thermal expansion property of the Ni-Fe porous metal substrate is almost the same with that of LaGaO3 based oxide. LaGaO3 based electrolyte films are prepared by the pulsed laser deposition (PLD) method. The film composition is sensitively affected by the deposition temperature. The obtained film is amorphous state after deposition. After post annealing at 1073 K in air, the single phase of LaGaO3 perovskite was obtained. Since the thermal expansion coefficient of the film is almost the same with that of LSGM film, the obtained metal support LSGM film cell shows the high tolerance against a thermal shock and after 6 min startup from room temperature, the cell shows the almost theoretical open circuit potential. LaGaO3 thin film was prepared on Ni-Fe metal porous substrate by Pulsed Laser Deposition method. By the thermal reduction, the dense NiO-Fe3O4 substrate is changed to a porous Ni-Fe metal substrate. The volumetric shrinkage and porosity of the substrate are controlled by the reduction temperature. It was found that a thermal expansion property of the Ni-Fe porous metal substrate is almost the same with that of LaGaO3 based oxide. LaGaO3 based electrolyte films are prepared by the pulsed laser deposition (PLD) method. The film composition is sensitively affected by the deposition temperature. The obtained film is amorphous state after deposition. After post annealing at 1073 K in air, the single phase of LaGaO3 perovskite was obtained. Since the thermal expansion coefficient of the film is almost the same with that of LSGM film, the obtained metal support LSGM film cell shows the high tolerance against a thermal shock and after 6 min startup from room temperature, the cell shows the almost theoretical open circuit potential.
Ju, Young-Wan,Matsumoto, Hiroshige,Ishihara, Tatsumi,Inagaki, Toru,Eto, Hiroyuki The Korean Ceramic Society 2008 한국세라믹학회지 Vol.45 No.12
$LaGaO_3$ thin film was prepared on Ni-Fe metal porous substrate by Pulsed Laser Deposition method. By the thermal reduction, the dense $NiO-{Fe_3}{O_4}$ substrate is changed to a porous Ni-Fe metal substrate. The volumetric shrinkage and porosity of the substrate are controlled by the reduction temperature. It was found that a thermal expansion property of the Ni-Fe porous metal substrate is almost the same with that of $LaGaO_3$ based oxide. $LaGaO_3$ based electrolyte films are prepared by the pulsed laser deposition (PLD) method. The film composition is sensitively affected by the deposition temperature. The obtained film is amorphous state after deposition. After post annealing at 1073K in air, the single phase of $LaGaO_3$ perovskite was obtained. Since the thermal expansion coefficient of the film is almost the same with that of LSGM film, the obtained metal support LSGM film cell shows the high tolerance against a thermal shock and after 6 min startup from room temperature, the cell shows the almost theoretical open circuit potential.
Pd 나노입자의 자가 회복이 가능한 지능형 페로브스카이트 산화물 음극의 직접 탄화수소계 SOFC 성능 평가
오미영,신태호,Oh, Mi Young,Ishihara, Tatsumi,Shin, Tae Ho 한국전기전자재료학회 2018 전기전자재료학회논문지 Vol.31 No.5
Nanomaterials have considerable potential to solve several key challenges in various electrochemical devices, such as fuel cells. However, the use of nanoparticles in high-temperature devices like solid-oxide fuel cells (SOFCs) is considered problematic because the nanostructured surface typically prepared by deposition techniques may easily coarsen and thus deactivate, especially when used in high-temperature redox conditions. Herein we report the synthesis of a self-regenerated Pd metal nanoparticle on the perovskite oxide anode surface for SOFCs that exhibit self-recovery from their degradation in redox cycle and $CH_4$ fuel running. Using Pd-doped perovskite, $La(Sr)Fe(Mn,Pd)O_3$, as an anode, fairly high maximum power densities of 0.5 and $0.2cm^{-2}$ were achieved at 1,073 K in $H_2$ and $CH_4$ respectively, despite using thick electrolyte support-type cell. Long-term stability was also examined in $CH_4$ and the redox cycle, when the anode is exposed to air. The cell with Pd-doped perovskite anode had high tolerance against re-oxidation and recovered the behavior of anodic performance from catalytic degradation. This recovery of power density can be explained by the surface segregation of Pd nanoparticles, which are self-recovered via re-oxidation and reduction. In addition, self-recovery of the anode by oxidation treatment was confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM).
Yoo, Seonyoung,Jun, Areum,Ju, Young‐,Wan,Odkhuu, Dorj,Hyodo, Junji,Jeong, Hu Young,Park, Noejung,Shin, Jeeyoung,Ishihara, Tatsumi,Kim, Guntae WILEY‐VCH Verlag 2014 Angewandte Chemie Vol.126 No.48
<P><I><B>Doppelperowskite</B></I> werden von G. Kim und Mitarbeitern in ihrer Zuschrift auf S. 13280 ff. als eine neue Klasse von Kathodenmaterialien für Festoxid‐Brennstoffzellen vorgestellt. Die verbesserte Stabilität von NdBa<SUB>0.75</SUB>Ca<SUB>0.25</SUB>Co<SUB>2</SUB>O<SUB>5+<I>δ</I></SUB> beruht auf der erhöhten Elektronenaffinität der beweglichen Sauerstoffspezies sowie der höheren Redoxstabilität, die durch Ca‐Dotierung an den A‐Positionen von NdBaCo<SUB>2</SUB>O<SUB>5+<I>δ</I></SUB> erreicht wird.</P>
Honeycomb-Like Perovskite Oxide Electrocatalyst for a Hybrid Li-Air Battery
Ju, Young-Wan,Yoo, Seonyoung,Guo, Limin,Kim, Changmin,Inoishi, Atsushi,Jeong, HuYoung,Shin, Jeeyoung,Ishihara, Tatsumi,Yim, Sung-Dae,Kim, Guntae The Electrochemical Society 2015 Journal of the Electrochemical Society Vol.162 No.14
<P>Honeycomb-like Nd<SUB>0.7</SUB>Sr<SUB>0.3</SUB>CoO<SUB>3−δ</SUB> has been successfully prepared with a PMMA hard-template for an energy storage system and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and nitrogen adsorption–desorption measurements. The prepared 3-dimensionally (3-D) ordered mesoporous Nd<SUB>0.7</SUB>Sr<SUB>0.3</SUB>CoO<SUB>3−δ</SUB> (3DOM-NSC) has a well-developed mesoporous structure and has high specific surface area (22.0 m<SUP>2</SUP> g<SUP>−1</SUP>). The catalytic activity for the oxygen reduction reaction (ORR) in 0.1 M KOH solution has been studied by using a rotating-ring-disk electrode (RRDE). In the ORR test, a limiting current density of 5.83 mA cm<SUP>−2</SUP> at 0.7 V (vs. Hg/HgO) with 1600 rpm was obtained, a value comparable with that of Pt/C. Moreover, the ORR mainly favors a direct four-electron pathway. Consequently, the high electrocatalytic activity and mesoporous structure result in stable, excellent performance in a hybrid Li-air cell.</P>
Ju, Young-Wan,Jun, Areum,Inoishi, Atsushi,Ida, Shintaro,Lim, Tak-hyoung,Kim, Guntae,Ishihara, Tatsumi The Electrochemical Society 2014 Journal of the Electrochemical Society Vol.161 No.6
<P>Layered perovskites have attracted abundant interest as advanced cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs) due to their high electrical conductivity and excellent catalytic properties for the oxygen reduction reaction (ORR). However, cobalt related layer perovskite oxides generally suffer from larger thermal expansion co-efficiency (TEC) than that of electrolyte materials. In this study, we have prepared a thin interlayer, SmBa<SUB>0.5</SUB>Sr<SUB>0.5</SUB>Co<SUB>2</SUB>O<SUB>5+<I>δ</I></SUB> (SBSCO) layered perovskite, via pulsed laser deposition (PLD) on a Sr- and Mg- doped LaGaO<SUB>3</SUB> (LSGM) thin film electrolyte to prevent the formation of a micro-gap arising from the thermal mismatch between the SBSCO cathode and LSGM electrolyte. A Samaria-doped ceria (SDC) buffer layer was prepared between the cathodic interlayer and LSGM electrolyte in order to prevent interdiffusion of cations. The cathodic interlayer of SBSCO is helpful for overcoming the thermal mismatch between the SBSCO powder cathode and the LSGM electrolyte, and also shows high power generating properties and small area specific resistance under typical fuel cell operating conditions.</P>