title: Dynamic Octahedral Breathing in Oxygen-Deficient Ba(0.9)Co(0.7)Fe(0.2)Nb(0.1)O(3-δ) Perovskite Performing as a Cathode in Intermediate-Temperature SOFC.
abstract: Ba(0.9)Co(0.7)Fe(0.2)Nb(0.1)O(3-δ) outperforms as a cathode in solid-oxide fuel cells (SOFC), at temperatures as low as 700-750 °C. The microscopical reason for this performance was investigated by temperature-dependent neutron powder diffraction (NPD) experiments. In the temperature range of 25-800 °C, Ba(0.9)Co(0.7)Fe(0.2)Nb(0.1)O(3-δ) shows a perfectly cubic structure (a = a0), with a significant oxygen deficiency in a single oxygen site, that substantially increases at the working temperatures of a SOFC. The anisotropic thermal motion of oxygen atoms considerably rises with T, reaching B(eq) ≈ 5 Å(2) at 800 °C, with prolate cigar-shaped, anisotropic vibration ellipsoids that suggest a dynamic breathing of the octahedra as oxygen ions diffuse across the structure by a vacancies mechanism, thus implying a significant ionic mobility that could be described as a molten oxygen sublattice. The test cell with a La(0.8)Sr(0.2)Ga(0.83)Mg(0.17)O(3-δ) electrolyte (∼300 μm in thickness)-supported configuration yields a peak power density of 0.20 and 0.40 W cm(-2) at temperatures of 700 and 750 °C, respectively, with pure H2 as fuel and ambient air as oxidant. The electrochemical impedance spectra (EIS) evolution with time of the symmetric cathode fuel cell measured at 750 °C shows that the Ba(0.9)Co(0.7)Fe(0.2)Nb(0.1)O(3-δ) cathode possesses a superior ORR catalytic activity and long-term stability. The mixed electronic-ionic conduction properties of Ba(0.9)Co(0.7)Fe(0.2)Nb(0.1)O(3-δ) account for its good performance as an oxygen-reduction catalyst.
authors.affiliation: Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences , Beijing 100190, China.
authors.forename: Yudong
authors.initials: Y
authors.lastname: Gong
authors.affiliation: Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences , Beijing 100190, China.|Beijing Institute of Nanoenergy and Nanosystems , Chinese Academy of Sciences, National Center for Nanoscience and Technology (NCNST), Beijing 100083, China.
authors.forename: Chunwen
authors.initials: C
authors.lastname: Sun
authors.affiliation: Physics and Electronic Technology, Hubei University , Wuhan, Hubei 430062, P. R. China.
authors.forename: Qiu-an
authors.initials: QA
authors.lastname: Huang
authors.affiliation: Instituto de Ciencia de Materiales de Madrid , CSIC, Cantoblanco, 28049 Madrid, Spain.
authors.forename: Jose Antonio
authors.initials: JA
authors.lastname: Alonso
authors.affiliation: Institut Laue Langevin , BP 156X, Grenoble Cedex, France.
authors.forename: Maria Teresa
authors.initials: MT
authors.lastname: Fernández-Díaz
authors.affiliation: Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences , Beijing 100190, China.
authors.forename: Liquan
authors.initials: L
authors.lastname: Chen