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RISS 인기검색어
- 검색키워드
- 저자 : Sossina Haile (검색결과 3 건)
- 무료
- 기관 내 무료
- 유료
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High Electrochemical Activity of Bi2O3-based Composite SOFC Cathodes
정우철,Yun-Jie Chang,Kuan-Zong Fung,Sossina Haile 한국세라믹학회 2014 한국세라믹학회지 Vol.51 No.4
Due to high ionic conductivity and favorable oxygen electrocatalysis, doped Bi2O3 systems are promising candidates as solidoxide fuel cell cathode materials. Recently, several researchers reported reasonably low cathode polarization resistance by addingelectronically conducting materials such as (La,Sr)MnO3 (LSM) or Ag to doped Bi2O3 compositions. Despite extensive researchefforts toward maximizing cathode performance, however, the inherent catalytic activity and electrochemical reaction pathways ofthese promising materials remain largely unknown. Here, we prepare a symmetrical structure with identically sized Y0.5Bi1.5O3/LSM composite electrodes on both sides of a YSZ electrolyte substrate. AC impedance spectroscopy (ACIS) measurements of electrochemicalcells with varied cathode compositions reveal the important role of bismuth oxide phase for oxygen electrocatalysis. These observations aid in directing future research into the reaction pathways and the site-specific electrocatalytic activity aswell as giving improved guidance for optimizing SOFC cathode structures with doped Bi2O3 compositions.
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Jung, WooChul,Gu, Kevin L.,Choi, Yoonseok,Haile, Sossina M. The Royal Society of Chemistry 2014 Energy & environmental science Vol.7 No.5
<P>Metal nanoparticles are of significant importance for chemical and electrochemical transformations due to their high surface-to-volume ratio and possible unique catalytic properties. However, the poor thermal stability of nano-sized particles typically limits their use to low temperature conditions (<500 °C). Furthermore, for electrocatalytic applications they must be placed in simultaneous contact with percolating ionic and electronic current transport pathways. These factors have limited the application of nanoscale metal catalysts (diameter <5 nm) in solid oxide fuel cell (SOFC) electrodes. Here we overcome these challenges of thermal stability and microstructural design by stabilizing metal nanoparticles on a scaffold of Sm<SUB>0.2</SUB>Ce<SUB>0.8</SUB>O<SUB>2−<I>δ</I></SUB> (SDC) films with highly porous and vertically-oriented morphology, where the oxide serves as a support, as a mixed conducting transport layer for fuel electro-oxidation reactions, and as an inherently active partner in catalysis. The SDC films are grown on single crystal YSZ electrolyte substrates by means of pulsed-laser deposition, and the metals (11 μg cm<SUP>−2</SUP> of Pt, Ni, Co, or Pd) are subsequently applied by D.C. sputtering. The resulting structures are examined by TEM, SIMS, and electron diffraction, and metal nanoparticles are found to be stabilized on the porous SDC structure even after exposure to 650 °C under humidified H<SUB>2</SUB> for 100 h. A.C. impedance spectroscopy of the metal-decorated porous SDC films reveals exceptionally high electrochemical reaction activity toward hydrogen electro-oxidation, as well as, in the particular case of Pt, coking resistance when CH<SUB>4</SUB> is supplied as the fuel. The implications of these results for scalable and high performance thin-film-based SOFCs at reduced operating temperature are discussed.</P> <P>Graphic Abstract</P><P>Combination of nanostructured ceria and nanoscale metal particles leads to unprecedented activity for hydrogen and methane electro-oxidation along with excellent morphological stability. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c3ee43546f'> </P>
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High Electrochemical Activity of Bi<sub>2</sub>O<sub>3</sub>-based Composite SOFC Cathodes
Jung, Woo Chul,Chang, Yun-Jie,Fung, Kuan-Zong,Haile, Sossina The Korean Ceramic Society 2014 한국세라믹학회지 Vol.51 No.4
Due to high ionic conductivity and favorable oxygen electrocatalysis, doped $Bi_2O_3$ systems are promising candidates as solid oxide fuel cell cathode materials. Recently, several researchers reported reasonably low cathode polarization resistance by adding electronically conducting materials such as (La,Sr)$MnO_3$ (LSM) or Ag to doped $Bi_2O_3$ compositions. Despite extensive research efforts toward maximizing cathode performance, however, the inherent catalytic activity and electrochemical reaction pathways of these promising materials remain largely unknown. Here, we prepare a symmetrical structure with identically sized $Y_{0.5}Bi_{1.5}O_3$/LSM composite electrodes on both sides of a YSZ electrolyte substrate. AC impedance spectroscopy (ACIS) measurements of electrochemical cells with varied cathode compositions reveal the important role of bismuth oxide phase for oxygen electrocatalysis. These observations aid in directing future research into the reaction pathways and the site-specific electrocatalytic activity as well as giving improved guidance for optimizing SOFC cathode structures with doped $Bi_2O_3$ compositions.
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