Lowering the Impedance of Lanthanum Strontium Manganite-Based Electrodes with Lanthanum Oxychloride and Lanthanum Scavenging Chloride Salts

Abstract

The impact of infiltrating chloride salts on the electrochemical behavior of lanthanum strontium manganite-yttria stabilized zirconia (LSM-YSZ) cathodes was investigated under solid oxide fuel cell operation. Infiltrating a lanthanum chloride solution resulted in the formation of a lanthanum oxychloride (LaOCl) phase. A LaOCl phase also formed by infiltrating an ammonium chloride solution; however, lanthanum was scavenged from the LSM phase to form LaOCl. The third infiltrating solution, a combination of zirconium chloride and yttrium nitrate, formed LaOCl by scavenging lanthanum from LSM and produced YSZ nanoparticles. Electrochemical impedance spectroscopy results suggest that LaOCl improves oxygen adsorption kinetics compared to a baseline LSM-YSZ cathode, reducing the low frequency impedance by 30%. In addition, scavenging lanthanum from LSM improved oxygen ion diffusion polarization as indicated by the observed 40% reduction in high frequency impedance and improved serial ohmic resistance by 19%. Finally, YSZ nanoparticles further reduced the high frequency impedance and ohmic resistance by 45% and 23%, respectively. The findings reveal new strategies for lowering the impedance of LSM-YSZ cathodes.

Overview of Approaches to Increase the Electrochemical Activity of Conventional Perovskite Air Electrodes

“…The enhancement of the electrochemical performance of (La 0.8 Sr 0.2 ) 0.95 MnO 3 − δ ((LSM20 0.95 )-YSZ cathodes by infiltrating salt solutions was reported in [382]. The developed 50LSM20 0.95 -50YSZ cathodes were characterized by the reduction of the highfrequency polarization resistance up to 45% of the baseline (R p(hf) = 1.06 Ω cm 2 at 700 • C for the YSZ infiltrated electrode), and the low-frequency polarization resistance up to 28% of the baseline (R p(lf) = 0.57 Ω cm 2 at 700 • C for the ammonium chloride infiltrated electrode).…”

“…To increase the electrochemical activity of LSM air electrodes, their compositions with ionic conductors were applied, e.g., with solid electrolytes (YSZ [205,303,352,[372][373][374][375][376][377][378][379][380][381][382][383], YSZ with GDC10 [374], SSZ [149,[384][385][386][387][388][389][390], GDC10 [391], GDC [152,198], SDC [148,149,387,392,393], doped Bi 2 O 3 [151,[394][395][396][397][398][399], BaZr 0.85 Y 0.15 O 3 − δ (BZY15) [154], LWO56 [156], LSGM [400,401]), or MIEC materials (Co- [150,402] and Fe-based perovskites [403][404][405]). The optimu...…”

“…The effective approach to increase the electrochemical activity of the conventional perovskite electrodes by increasing the TPB is related to the preparation of decorated electrodes by the infiltration (also called impregnation) method, where the porous cathode is filled with various additives [148,163,304,323,340,382,403,[434][435][436][437][438] as well as decorating the electrode surface with nanocatalysts [141,154,315,387,405,416,426,439] and nanocoatings [303,308,341,342], which significantly improve the electrode surface diffusion and exchange with the gas phase.…”