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Kompleksowy przegląd metod preparatyki, właściwości i zastosowań fotokatalitycznych różnych struktur perowskitowych

Miodyńska Magdalena, Cavdar Onur, Pancielejko Anna

Wiadomości Chemiczne

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2024

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[Z] 78, 3-4

243--262

EN

Perovskite materials for photocatalytic environmental and energy conversion applications have drawn excessive attention over recent years owing to their unique photoelectric and catalytic properties. As harvesting solar energy within the bounds of possibility is one of the main aims of photocatalysis, many research groups have devoted their efforts to developing perovskite-based photocatalytic materials from perovskite oxide to metal halide and double halide-based perovskite materials with various synthesis strategies. Particularly, halide and double halide-based perovskites are intriguing thanks to their tunable band gap and band structure depending on the type of halide. Apart from the obstacles related to charge separation and transport processes; instability under water, oxygen, and high temperature hindering their practical photocatalytic application are remaining challenges. Toxicity emerging from Pb2+ or Sn2+ release due to chemical instability is another concern to be tackled. Thusfar, replacing Pb2+ or Sn2+ with Bi3+ is one of the currentscopesin the perovskite photocatalysis area while ensuring chemical stability in halide-based perovskites and thus reducing toxicity. Despite all those challenges, the popularity of perovskite photocatalysis is growing amid the favorable light induced chemical reactions via a plentiful range of promising cost-effective manufacturing methods of perovskites. In this review, the principles and photocatalytic applications of the perovskite oxides, metal halide-based perovskites, and double halide-based are comprehensively discussed.

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Structural Properties of SrCo0.2Fe0.8O3–delta Oxide: Oxygen Nonstoichiometry, Vacancy Ordering and Broken Local Symmetry

Świerczek K., Marzec J.

Polish Journal of Chemistry

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2009

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Vol. 83, nr 8

1489-1496

EN

Results of X-ray, Mössbauer and thermogravimetric studies per formed for SrCo0.2Fe0.8O3-delta oxide are presented. The initial “as prepared”, vacancy ordered, orthorhombic SrCo0.2Fe0.8O2.75 upon reduction at high temperatures in low hydrogen content, H2/Ar gas mixture, transforms into brownmillerite type SrCo0.2Fe0.8O2.5. While heating in air, at around 400 graduate C, SrCo0.2Fe0.8O2.5 transforms into distorted cubic structure. This trans formation is accompanied by a massive oxygen up take (similar to 0.28 mol/mol). Further heating of the sample leads to a decrease of the oxygen content. Additionally, Rietveld refinement of the XRD data indicates practically no distortion of the cubic structure at 800 graduate C. Upon cooling, the initial orthorhombic SrCo0.2Fe0.8O2.75 structure is rebuilt. Local hyperfine inter actions within the B sublattice of the perovskite structured SrCo0.2Fe0.8O2.75, which were studied by means of transmission 57Fe Mössbauer spectroscopy, revealed presence of an unexpected, high electric field gradient. This can be ascribed to a significantly lower local symmetry brought about by the presence of or ered oxygen vacancies.

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Oxygen Nonstoichiometry and Transport Properties of Selected La1-xSrxCo1-y-zFeyNizO3-delta Perovskites

Świerczek K.

Polish Journal of Chemistry

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2009

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Vol. 83, nr 8

1437-1442

EN

Crystal structure, high temperature oxygen nonstoichiometry and transport properties of two members of La1-xSrxCo1-y-zFeyNizO3-delta group of perovskite type oxides are presented. La0.6Sr0.4Co0.2Fe0.6Ni0.2O3-delta and La0.9Sr0.1Co1/3Fe1/3Ni1/3O3-delta compositions po sess high electrical conductivity at high temperatures in air. How ever, the observed characteristics of the electrical conductivity as a function of the oxygen partial pressure for these materials are significantly different. A discussion of the observed effects is provided, which shows strong correlation between chemical composition, crystal structure, oxygen nonstoichiometry and the observed transport properties. An interesting phenomenon related to an irreversible oxygenation of the quenched La0.6Sr0.4Co0.2Fe0.6Ni0.2O3-delta samples was observed. This reaction takes place at 200–300 graduate C range which is well below a typical nonstoichiometry related reactions. A possible explanation of this effect is discussed.

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Evaluation of La0.5Sr0.5Co0.5Fe0.25Mn0.25O3-delta Perovskite-Type Oxide as the Cathode Material for Solid Oxide Fuel Cells

Molenda J., Krupiński J., Zając W., Świerczek K.

Polish Journal of Chemistry

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2009

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Vol. 83, nr 8

1497-1506

EN

An evaluation of La0.5Sr0.5Co0.5Fe0.25Mn0.25O3–delta perovskite type oxide as the cathode material for Solid Ox ide Fuel Cells (SOFC) is presented. La0.5Sr0.5Co0.5Fe0.25Mn0.25O3-delta was prepared using high temperature solid state reaction. We show results of structural, thermogravimetric, low temperature and high temperature transport properties, together with high temperature chemical reactivity studies in relation to zirconia and ceria based solid electrolytes. Additionally, we present results of testing of electrochemical properties of SOFC cell based on ceria type electrolyte and La0.5Sr0.5Co0.5Fe0.25Mn0.25O3-delta cathode material.