Chemical compatibility of solid oxide fuel cell air electrode Pr4Ni3O10±δ with commercial electrolytes

The chemical reactivity between Pr₄Ni₃O_10±δ (3-PNO) electrodes and Y_0.08Zr_0.92O_1.96 (YSZ), Ce_0.9Gd_0.1O_1.95 (GDC), and La_0.9Sr_0.1Ga_0.8Mg_0.2O_2.85 (LSGM) electrolytes was analyzed by electrochemical impedance spectroscopy and X-ray diffraction. 3-PNO powders were synthesized by two different chemical routes, one of them uses hexamethylenetetramine (HMTA) as a complexing agent (route A) while the other citrates (route B). The samples observed by scanning electron microscopy presented different microstructures; route A powders present small submicronic grains with an open microstructure while route B powders are formed by larger well-connected grains. The polarization resistance (R_P) values for 3-PNO/YSZ cells are one order of magnitude higher than those of 3-PNO/GDC and 3-PNO/LSGM cells. The R_P for both cells 3-PNO/GDC and 3-PNO/LSGM and its evolution in time suggest that chemical reactivity takes place during the adhesion treatment and electrochemical measurements. The microstructure plays a crucial role in R_P and the degradation rate; 3-PNO obtained by route A (3-PNO-HMTA) exhibits the best electrochemical performance since these powders present a well-loose morphology and a large exposed area. However, this fact makes them active chemically, so the increase of R_P with time is slower for 3-PNO electrodes prepared by route B (3-PNO-Cit), since the rate of chemical reactivity with the electrolyte is slower.