Ag surface-coated with nano-YSZ as an alternative to Pt catalyst for low-temperature solid oxide fuel cells

Kim, Dong Hwan,Bae, Kiho,Choi, Hyung Jong,Shim, Joon Hyung Elsevier 2018 JOURNAL OF ALLOYS AND COMPOUNDS Vol.769 No.-

<P><B>Abstract</B></P> <P>Herein we propose silver surface-coated with nano-scale yttria-stabilized zirconia (YSZ) as a high-performance cathode for use in low-temperature solid oxide fuel cells (LT-SOFCs). YSZ was coated on the Ag cathode surface by sputtering of Y/Zr alloy films followed by thermal annealing for oxidation of YSZ. An electrolyte-support type SOFC was fabricated on 350-μm-thick gadolinium-doped ceria (GDC) pellets. The yttrium concentration and sputtering time for obtaining the YSZ coating layer was varied to optimize the cathode composition. It was determined that the GDC SOFCs with optimized Ag-YSZ cathodes significantly outperform cells with bare silver or platinum cathodes, which are considered to be the best-performing catalysts at low temperatures. The peak power density obtained using cells with Ag-YSZ cathodes was as high as ∼100 mW/cm<SUP>2</SUP> at 450 °C, 3–4 times greater than the performance of cells with Ag or Pt cathodes. Electrochemical impedance spectroscopy was performed during fuel cell testing to compare polarization and charge transport performances of the Ag-YSZ cathodes. The long-term stability of the Ag-YSZ cathode was evaluated by monitoring the change in cathode morphology compared to the bare Ag and Pt cathodes.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ag cathode surface-coated with nano-YSZ is prepared by sputtering. </LI> <LI> Ag-YSZ cathode outperforms Ag and Pt in terms of fuel cell performance. </LI> <LI> GDC pellet cells with Ag-YSZ achieves over 100 mW/cm<SUP>2</SUP> at 450 °C. </LI> <LI> YSZ surface-coating helps enhancement of electrochemical surface kinetics. </LI> </UL> </P>

Durable and High-Performance Direct-Methane Fuel Cells with Coke-Tolerant Ceria-Coated Ni Catalysts at Reduced Temperatures

Lee, Jin Goo,Jeon, Ok Sung,Hwang, Ho Jung,Jang, Jeongseok,Lee, Yeayeon,Hyun, Sang Hoon,Shul, Yong Gun Elsevier 2016 ELECTROCHIMICA ACTA Vol.191 No.-

<P><B>Abstract</B></P> <P>Natural gas constitutes a promising energy source in the intermediate future because of the existing supply infrastructure and ease of storage and transportation. Although a solid oxide fuel cell can directly convert chemical energy stored in the hydrocarbon fuel into electrical energy at high temperatures, carbon formations on the nickel-based anode surfaces cause serious degradation of the long-term performance. Here, we report highly coke-tolerant ceria-coated Ni catalysts for low-temperature direct-methane fuel cells. The catalyst shows the high activity for CO oxidations, which is beneficial to avoid carbon formations induced by CO disproportionation at low temperatures. When the ceria-coated Ni catalysts were applied to the solid oxide fuel cells as a catalyst layer, the cell generates a power output of 1.42Wcm<SUP>-2</SUP> at 610°C in dry methane and operates over 1000h at a current density of 1.2Acm<SUP>-2</SUP>.</P> <P><B>Highlights</B></P> <P> <UL> <LI> GDC-coated NiO catalysts are prepared by hydrothermal synthesis. </LI> <LI> The GDC-coated NiO catalysts show high coking tolerances and catalytic activity for CH<SUB>4</SUB> and CO oxidations. </LI> <LI> Direct-methane solid oxide fuel cells with the GDC-coated NiO catalyst layer are stable with high performances in CH<SUB>4</SUB> for 1000h. </LI> <LI> Covering the Ni surfaces with the GDC nano-particles may successfully suppress the growth of carbon seeds on the Ni surfaces. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Atomic-layer-deposited ZrO₂-doped CeO₂ thin film for facilitating oxygen reduction reaction in solid oxide fuel cell

Yang, Byung Chan,Go, Dohyun,Oh, Seongkook,Woo Shin, Jeong,Kim, Hyong June,An, Jihwan Elsevier 2019 APPLIED SURFACE SCIENCE - Vol.473 No.-

<P><B>Abstract</B></P> <P>Ultra-thin ZrO<SUB>2</SUB>-doped CeO<SUB>2</SUB> (ZDC) interlayers (20 nm thick) with varying doping ratios of 0, 20, and 60 mol% were prepared using atomic layer deposition (ALD), and were investigated as cathodic interlayers for low-temperature solid oxide fuel cells (LT-SOFCs). The inclusion of ZrO<SUB>2</SUB> in CeO<SUB>2</SUB> film induced the reduction of Ce<SUP>4+</SUP> to Ce<SUP>3+</SUP> with higher concentration of oxygen vacancies, and also enhanced the resistance of the film to the coarsening at elevated temperature (800 °C), well preserving the nanoscale fine grain structure. As a result, the maximum power density of the cell with 20 mol%-doped ZDC interlayer improved by 57% compared to the cell without the interlayer due to enhanced activation process at the cathode, which seems to be due to higher oxygen vacancy population as well as higher grain boundary density at the electrolyte-cathode interface.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Doping level in ZrO<SUB>2</SUB>-doped CeO<SUB>2</SUB> was precisely controlled by atomic layer deposition. </LI> <LI> ZrO<SUB>2</SUB> doping reduces Ce<SUP>4+</SUP> to Ce<SUP>3+</SUP> increasing oxygen vacancy content in CeO<SUB>2</SUB> lattice. </LI> <LI> ZrO<SUB>2</SUB> doping suppresses the grain growth leading to smaller grains upon annealing. </LI> <LI> The cell performance with ZrO<SUB>2</SUB>-doped CeO<SUB>2</SUB> cathodic interlayer improves by 57%. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Nanometer Yttria-doped Ceria Shell by Atomic Layer Deposition over Porous Pt for Improved Oxygen Reduction Reactions

Jeong Woo Shin,Sungje Lee,Dohyun Go,Byung Chan Yang,Taeyoung Kim,Sung Eun Jo,Pei-Chen Su,Jihwan An 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.10 No.3

Designing highly active and thermally stable electrodes is crucial for realizing low-temperature solid oxide fuel cells (LT-SOFCs) with excellent performance. In this study, we fabricated an yttria-doped ceria (YDC) shell layer by atomic layer deposition (ALD) over a Pt cathode by controlling the doping concentration of yttria in YDC film. The exchange current density was enhanced by a factor of five when the ALD YDC shell layer was deposited onto the cathode surface compared to the bare Pt cathode, resulting in an 80% decrease in the activation resistance of the 19 mol%-doped ALD YDC-overcoated Pt cathode compared to that of the bare Pt cathode. Furthermore, the thermal stability was enhanced in low-to-medium-doped (7–19 mol%) ALD YDC-coated Pt cathodes, whereas the highly doped (31 mol%) cathode showed a relatively marginal improvement in stability.

Electrochemical properties of electrospinning-fabricated layered perovskite used in cathode materials for a low temperature-operating solid oxide fuel cell

Jin, Sangbeom,Choi, Won Seok,Baek, Seung-Wook,Shin, Tae Ho,Park, Jun-Young,Kim, Jung Hyun Elsevier 2018 THIN SOLID FILMS - Vol.660 No.-

<P><B>Abstract</B></P> <P>In this study, the microstructural and electrochemical properties of linear type nanofibers obtained by adding SmBa<SUB>0.5</SUB>Sr<SUB>0.5</SUB>Co<SUB>2</SUB>O<SUB>5+d</SUB> (SBSCO) layered perovskite oxide were investigated for use as cathode materials in a low temperature-operating solid oxide fuel cell.</P> <P>Linear type SBSCO fiber and Ce<SUB>0.9</SUB>Gd<SUB>0.1</SUB>O<SUB>2−d</SUB> coated SBSCO-fiber were fabricated using the electrospinning process. It was confirmed that the area specific resistance (0.75 Ω cm<SUP>2</SUP>) of the obtained SBSCO-fiber cathode was much lower than that (1.25 Ω cm<SUP>2</SUP>) of a powder-type SBSCO cathode at 550 °C. The result shows that the SBSCO fiber cathode exhibits lower polarization resistance in low temperature ranges than the powder SBSCO cathode materials do. A significantly lower activation energy (0.76 eV) was observed in fiber SBSCO cathode than in the nanostructured La<SUB>0.8</SUB>Sr<SUB>0.2</SUB>Co<SUB>0.2</SUB>Fe<SUB>0.8</SUB>O<SUB>3−d</SUB> ones which were used as control at 1.53 eV.</P> <P><B>Highlights</B></P> <P> <UL> <LI> SmBa<SUB>0.5</SUB>Sr<SUB>0.5</SUB>Co<SUB>2</SUB>O<SUB>5+d</SUB> (SBSCO) nanofibers (SBSCO-F) were fabricated. </LI> <LI> The SBSCO-F sample showed the lowest ASR value: 0.75 Ω cm<SUP>2</SUP> at 550 °C. </LI> <LI> The SBSCO-F sample showed the lowest activation energy: 0.76 eV. </LI> <LI> The SBSCO-F can be considered an optimized cathode material for LT-SOFCs. </LI> </UL> </P>

Sintered powder-base cathode over vacuum-deposited thin-film electrolyte of low-temperature solid oxide fuel cell: Performance and stability

Park, Jung Hoon,Han, Seung Min,Kim, Byung-Kook,Lee, Jong-Ho,Yoon, Kyung Joong,Kim, Hyoungchul,Ji, Ho-Il,Son, Ji-Won Elsevier 2019 ELECTROCHIMICA ACTA Vol.296 No.-

<P><B>Abstract</B></P> <P>To expand the processing options for low-temperature-operating solid oxide fuel cells (LT-SOFCs), the hybridization of powder processing and vacuum deposition is attempted. Nanostructured nickel-yttria-stabilized zirconia (Ni-YSZ) anode functional layer (AFL) and YSZ/gadolinia-doped ceria (GDC) bi-layer electrolyte are fabricated over a sintered anode support by pulsed laser deposition (PLD), a physical vapor deposition technology. The most common powder-processed (screen-printed and sintered) La<SUB>0.6</SUB>Sr<SUB>0.4</SUB>Co<SUB>0.2</SUB>Fe<SUB>0.8</SUB>O<SUB>3-δ</SUB>-Gd<SUB>0.1</SUB>Ce<SUB>0.9</SUB>O<SUB>1.95</SUB> (LSCF-GDC) composite cathode is applied over vacuum-deposited thin-film components. When LSCF-GDC is sintered at a general sintering temperature of 1050 °C then the continuity of the GDC buffer is lost and excessive interdiffusion between the cathode and the electrolyte has occurred at the interface. On the other hand, if the sintering temperature is lowered to 950 °C, peak power density more than 1.7 W cm<SUP>−2</SUP> at 650 °C is obtained. Moreover, the operation stability of the hybrid SOFC (degradation rate ∼8%/100 h) is superior to that of the SOFC with a vacuum-processed nanostructure cathode (degradation rate ∼21%/100 h) when exposed to 0.7 A cm<SUP>−2</SUP> at 650 °C, which is a significantly harsh degradation test condition for LT-SOFCs.</P>

Co-sputtered nanocomposite nickel cermet anode for high-performance low-temperature solid oxide fuel cells

Lim, Yonghyun,Lee, Hojae,Hong, Soonwook,Kim, Young-Beom Elsevier 2019 Journal of Power Sources Vol.412 No.-

<P><B>Abstract</B></P> <P>Nickel-samaria-doped ceria (Ni-SDC) nanocomposite anodes with various compositions are fabricated by co-sputtering technique. The film compositions are effectively controlled by adjusting the applied power to the SDC target while applying a constant power to the Ni target. The microstructure, crystallinity and electrical conductivity of the deposited films are analyzed and their optimal composition is investigated based on fuel cell performance and electrochemical impedance spectroscopy (EIS) analysis. Among various deposition conditions, the lowest polarization resistance is achieved at Ni-SDC 80W condition, which is attributed to the difference in the film composition and expected reaction site densities. Thin film fuel cells with the optimal nickel cermet anode are fabricated on a nanoporous supporting structure to achieve a high cell performance and compared with noble Pt electrode. The fuel cell with the optimal nickel cermet anode yields a maximum power density of 178 mW/cm<SUP>2</SUP> and polarization resistance of 0.55 Ω cm<SUP>2</SUP> at 450 °C, which is significantly improved from the reference Pt anode cell (113 mW/cm<SUP>2</SUP> and 1.69 Ω cm<SUP>2</SUP>). Impedance analysis clearly demonstrates that the enhancement in the cell performance originates from the difference in the polarization resistance, resulting from the expanded reaction sites owing to the mixed ion electronic conducting characteristics of the nickel cermet nanocomposite anode.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ni-SDC nanocomposite anodes are fabricated by co-sputtering method. </LI> <LI> Optimal condition of the anode is investigated based on electrochemical performance. </LI> <LI> The expanded anode reaction sites significantly enhanced the fuel cell performance. </LI> <LI> Remarkable LT-SOFC performance is reported without precious metal anode. </LI> </UL> </P>

Interface engineering of yttrium stabilized zirconia/gadolinium doped ceria bi-layer electrolyte solid oxide fuel cell for boosting electrochemical performance

Jang, Inyoung,Kim, Sungmin,Kim, Chanho,Lee, Hyungjun,Yoon, Heesung,Song, Taeseup,Paik, Ungyu Elsevier 2019 Journal of Power Sources Vol.435 No.-

<P><B>Abstract</B></P> <P>La<SUB>0.6</SUB>Sr<SUB>0.4</SUB>Co<SUB>0.2</SUB>Fe<SUB>0.8</SUB>O<SUB>3-δ</SUB> (LSCF) is a promising cathode material for solid oxide fuel cells due to its high oxygen reduction reaction (ORR) activity. A gadolinium-doped ceria (GDC) barrier layer is essential to preventing side reactions between LSCF and an yttrium-stabilized zirconia (YSZ) electrolyte. However, several challenges are associated with the coating of GDC barrier layer on the YSZ electrolyte, including delamination of the GDC layer due to sinterability differences and formation of an insulating layer at a high annealing temperature. In this study, we describe a structure for a newly designed interfacial layer consisting of a GDC barrier layer and a nano-web–structured LSCF thin-film layer (NW-LSCF) through a facile spin-coating method. A dense GDC barrier layer with a thickness of approximately 400 nm was successfully applied to the surface of a YSZ electrolyte without delamination at a low annealing temperature. The high surface area of the NW-LSCF enhanced ORR due to an increased triple-phase boundary length. Cells employing a GDC barrier layer and NW-LSCF interlayer exhibited improved electrochemical performance. Peak power density reached 1.29 W/cm<SUP>2</SUP> at an operating temperature of 550 °C and 2.14 W/cm<SUP>2</SUP> at 650 °C.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Newly designed interfacial layer structure is developed for interfacial engineering. </LI> <LI> Combined structure of GDC barrier layer/NW-LSCF improves electrochemical properties. </LI> <LI> The NW-LSCF enables higher oxygen reduction reaction at lower temperature. </LI> <LI> Results show the possibility of lowering SOFCs operating temperature. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

나노섬유 제작기술을 적용한 저온형 고체산화물 연료전지 이중층 페로브스카이트 나노섬유 공기극의 특성 분석

진상범(SangBeom Jin),김근수(Keunsoo Kim),백승욱(Seung-Wook Baek),김현석(Hyun-Suk Kim),강현일(Hyunil Kang),최원석(Wonseok Choi),김정현(Junghyun Kim) 한국신재생에너지학회 2017 신재생에너지 Vol.13 No.2

In this study, linear typed nanofibers were fabricated by controlling the variables with the great effects on nanofiber fabrication and the microstructural properties of fabricated nanofibers were investigated as a preliminary step to serve as a carrier, including SmBa<SUB>0.5</SUB>Sr<SUB>0.5</SUB>Co<SUB>2</SUB>O<SUB>5+d</SUB> (SBSCO) cathode materials for low temperature-operating solid oxide fuel cells (LT-SOFCs). Beadless nanofibers were produced at a nozzle to substrate distance of at least 9 cm when using the electrospinning process. The diameter of the nanofibers increased with increasing flow rate, and the diameter of the nanofibers also increased at a nozzle to substrate distance of 9cm or more. As the humidity increased, collapse of the nanofibers was observed. The fabricated nanofibers, as a carrier for SBSCO, were decomposed in three parts: a temperature range of RT~340°C, 340°C~454°C, and higher than 454°C. No further weight losses were observed at temperatures higher than 625°C. The lowest area specific resistance (ASR) was observed when SBSCO was used in the nanofiber type and the SBSCO nanofiber exhibited an ASR value of 0.85 Ω.cm<SUP>2</SUP>at 550°C.

A Study on the Optimization of RF Magnetron Co-sputtering of LSCF-GDC Cathode for Low-temperature Solid Oxide Fuel Cell Varying the Ratio of the Materials

S. Y. Choi(최상용),W. Y. Jeong(정원엽),I. W. Choi(최인원),S. W. Cha(차석원) Korean Society for Precision Engineering 2023 한국정밀공학회 학술발표대회 논문집 Vol.2023 No.5