Improvement of the Electrochemical Performance of Ln_0.58Sr_0.4Fe_0.8Co_0.2O_3 – δ IT‐SOFC Cathodes by Ternary Lanthanide Combinations (La‐Pr‐Sm)

Abstract

Active perovskite‐based SOFC cathodes have been developed through lanthanide combination in the (La1 – x – yPrxSmy)0.58Sr0.4Fe0.8Co0.2O3 – 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 Ln0.58Sr0.4Fe0.8Co0.2O3 – 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 Ln0.58Sr0.4Fe0.8Co0.2O3 – 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 Ln0.58Sr0.4Fe0.8Co0.2O3 – 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.

Compositional Improvement of Ln[sub 0.435]Ba[sub 0.145]Sr[sub 0.4]Fe[sub 0.8]Co[sub 0.2]O[sub 3−δ] IT-SOFC Cathodes Performance by Multiple Lanthanide Substitution

“…28 However, the Sm1SFC sample presents some impurities corresponding to the orthorhombic perovskite phase. 29 These Ln-Babased compositions have close lattice parameters among them, ranging from 3.865 to 3.890 Å. Small differences are obtained depending on the ratio of each lanthanide in the resulting perovskite.…”

Evaluation of double perovskite Sr2FeTiO6−δ as potential cathode or anode materials for intermediate-temperature solid oxide fuel cells

“…During the past, Cobalt containing oxides of different composition, such as Ln 1 À x Sr x Co 1 À y Fe y O 3 À δ (Ln=rare-earth) [8][9][10][11][12], Ba 1 À x Sr x Co 1 À y Fe y O 3 À δ [5,[13][14][15][16], LnBaCo 2 O 5 þ δ (Ln=rare-earth) [17][18][19][20][21], and RBa(Co, M) 4 O 7 (R=Y, Ca, In and M=Zn, Ga, Al) [22][23][24][25][26][27], have been extensively exploited as potential cathode materials for IT-SOFCs, owing to their excellent electrocatalytic activity for the oxygen reduction reaction (ORR). However, most of these materials usually show poor chemical stability, insufficient chemical compatibility with the electrolyte, high thermal expansion coefficient, high cost of cobalt element and easy evaporation.…”

Infrared emissivities and microwave absorption properties of perovskite Sm0.5Sr0.5Co1−xFexO3 (0≤x≤0.5)

“…Perovskite-type structure oxides (ABO 3 ) are widely used as cathode materials [12][13][14][15], gas sensors [16,17], new catalysts [18][19][20], for their high electrical conductivity, high dielectric constant, and high catalytic activity, which depend upon the different types and contents of metals occupying in the A and B sites [21][22][23]. Rare earth alkalide manganites show potentiality for thermochromic devices in the infrared range due to their charge * Corresponding author.…”