Phase Transition of a Cobalt‐Free Perovskite as a High‐Performance Cathode for Intermediate‐Temperature Solid Oxide Fuel Cells

Abstract

It is generally recognized that the phase transition of a perovskite may be detrimental to the connection between cathode and electrolyte. Moreover, certain phase transitions may induce the formation of poor electronic and ionic conducting phase(s), thereby lowering the electrochemical performance of the cathode. Here, we present a study on the phase transition of a cobalt-free perovskite (SrNb(0.1)Fe(0.9)O(3-δ), SNF) and evaluate its effect on the electrochemical performance of the fuel cell. SNF exists as a primitive perovskite structure with space group P4mm (99) at room temperature. As evidenced by in situ high-temperature X-ray diffraction measurements over the temperature range of 600 to 1000 °C, SNF undergoes a transformation to a tetragonal structure with a space group I4/m (87). This phase transition is accompanied by a moderate change in the volume, allowing a good cathode/electrolyte interface on thermal cycling. According to the electrochemical impedance spectroscopy evaluation, the I4/m phase exhibits positive effects on the cathode's performance, showing the highest oxygen reduction reaction activity of cobalt-free cathodes reported so far. This activity improvement is attributed to enhanced oxygen surface processes.

A Broad Stability Investigation of Nb-Doped SrCoO2.5+δas a Reversible Oxygen Electrode for Intermediate-Temperature Solid Oxide Fuel Cells

“…Table I compares R P values obtained by this study with the literature. [21][22][23][36][37][38][39][40][41][42] Overall, R P values of this study are at the same order of magnitude with the literature, but not the lowest, particularly at lower temperatures. The differences such as in particles size, microstructures and type of electrolyte could contribute to the differences observed.…”

ChemInform Abstract: Recent Development on Perovskite‐type Cathode Materials Based on SrCoO3‐δ. Parent Oxide for Intermediate‐Temperature Solid Oxide Fuel Cells

“…LSM), [22][23][24] Fe-based (e.g. SrFeO 3 À δ ), [25][26][27][28][29][30][31][32][33][34][35] Ni-based (e.g. LaNiO 3 À δ ), Co-based (e.g.…”

EuBaCo2O5+δ-Ce0.9Gd0.1O2−δ composite cathodes for intermediate-temperature solid oxide fuel cells: high electrochemical performance and oxygen reduction kinetics

“…The perovskite oxides have been considered as the most common cathode materials due to their mixed oxide-ion and electron conduction characteristic, which results in the high electrocatalytic activity for the ORR [6][7][8][9]. In recent years, double perovskite, LnBaCo 2 O 6Àd (Ln = lanthanide elements), have been investigated as a cathode candidate for IT-SOFCs [10][11][12][13][14][15][16][17][18][19][20][21][22] ] along the c axis.…”