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Improvement of the Electrochemical Performance of Ln 0.58 Sr 0.4 Fe 0.8 Co 0.2 O 3 – δ IT‐SOFC Cathodes by Ternary Lanthanide Combinations (La‐Pr‐Sm)
Author(s) -
Vert V. B.,
Serra J. M.
Publication year - 2010
Publication title -
fuel cells
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.485
H-Index - 69
eISSN - 1615-6854
pISSN - 1615-6846
DOI - 10.1002/fuce.200900166
Subject(s) - samarium , lanthanide , praseodymium , ternary operation , lanthanum , electrochemistry , materials science , cathode , dielectric spectroscopy , inorganic chemistry , electrode , analytical chemistry (journal) , chemistry , ion , metallurgy , organic chemistry , chromatography , computer science , programming language
Active perovskite‐based SOFC cathodes have been developed through lanthanide combination in the (La 1 – x – y Pr x Sm y ) 0.58 Sr 0.4 Fe 0.8 Co 0.2 O 3 – δ system following a ternary mixture experimental design. These compositions were prepared through a sol–gel method and characterised by electrochemical impedance spectroscopy (EIS) as symmetrical cells on GDC‐electrolyte samples in the 450–650 °C temperature range. The electrochemical properties of the single lanthanide‐based Ln 0.58 Sr 0.4 Fe 0.8 Co 0.2 O 3 – δ compounds were enhanced when different lanthanides were combined together in the same crystalline structure. The observed improvement does not follow a mere additional effect of the performance from the parent Ln 0.58 Sr 0.4 Fe 0.8 Co 0.2 O 3 – δ compounds, i.e. it does not follow a linear behaviour, and the better performance is ascribed to synergetic catalytic effects among lanthanide cations. A reduction in electrode polarisation resistance with respect to non‐substituted compositions is stated for most Ln 0.58 Sr 0.4 Fe 0.8 Co 0.2 O 3 – δ electrode compositions combining two or three lanthanides. Samarium addition to the electrode material involves a substantial reduction in the activation energy and the reduction degree is directly dependant on the samarium amount incorporated in the lattice. The best performing composition comprises a praseodymium‐rich lanthanum‐based electrode material. The experimental data derived from the ternary mixture design were modelled using nonlinear functions and this modelling allowed finding an electrode composition minimising the polarisation resistance while maintaining the activation energy at reduced values. Selected cathode compositions were tested in fully assembled anode‐supported cells and electrochemical characterisation supports the cooperative effect of lanthanide combination.