Development of Nanostructured and Palladium Promoted (La,Sr)MnO[sub 3]-Based Cathodes for Intermediate-Temperature SOFCs

Abstract

Nanostructured and palladium-promoted Sr-doped LaMnO 3 ͑LSM͒-based cathodes are developed via solution impregnation for intermediate-temperature solid oxide fuel cells ͑IT-SOFCs͒. Both the nanostructured and Pd-promoted LSM-based cathodes show significantly improved electrochemical performance compared to the conventional LSM/Y 2 O 3 -doped ZrO 2 YSZ composite cathode, with electrode polarization resistances of 1.5 and 0.9 ⍀ cm 2 at 600°C, respectively, in contrast to 70 ⍀ cm 2 obtained from the conventional LSM/YSZ cathode. Low activation energies are also obtained with the developed cathodes, indicating a promising applicability of such nanostructured and Pd-promoted electrodes as cathodes for the intermediate-temperature SOFCs.For solid oxide fuel cells ͑SOFCs͒ based on Y 2 O 3 -doped ZrO 2 ͑YSZ͒ electrolyte, Sr-doped LaMnO 3 ͑LSM͒ perovskite is a widely investigated cathode material because of its thermal and chemical compatibility with YSZ, high electrochemical activity for the O 2 reduction reaction, and high structural stability at high temperatures. 1-4 Numerous attempts have been undertaken to improve the performance of LSM-based cathodes by forming composite. [5][6][7][8][9][10][11][12][13] The conventional approach is to mix an ionic conducting phase, such as YSZ and Gd-doped CeO 2 ͑GDC͒, with electronic conducting LSM to extend the three-phase boundary ͑TPB͒ for the O 2 reduction reaction. Murray et al. 6,10 achieved a reduction in electrode polarization resistance to 15% of the pure LSM electrodes at 700°C by using LSM/YSZ and LSM/GDC composite electrodes. Another strategy is to develop nanostructured composite cathodes by wet impregnation. We have shown that impregnation of ionic conducting GDC particles into porous LSM cathode resulted in a substantial reduction in electrode polarization resistance, as compared to the conventional LSM/YSZ and LSM/GDC composite cathodes. 14,15 Huang et al. have also confirmed the enhancement with LSM-impregnated YSZ composite cathodes prepared at temperatures between 850 and 1250°C. 16 Addition of catalytically active nanoparticles onto the internal surfaces of porous electrodes can increase their performance by facilitating the electrochemical reaction processes on electrodes. [17][18][19][20] Recently we demonstrated substantially low electrode polarization resistance and reduced activation energy for the O 2 reduction reaction on Pd-impregnated YSZ composite cathodes in comparison with conventional LSM/YSZ, LSM/GDC, and mixed ionic and electronic conducting ͑MIEC͒ cathodes such as ͑La,Sr͒͑Co,Fe͒O 3 . 21 LSM has been known to be the most stable cathode material for high-temperature SOFCs; however, it becomes much less performed when the operation temperature is decreased to the intermediate range of 600-800°C due to the negligible ionic conductivity of LSM perovskites. 22 The purpose of this study is to engineer the microstructure and electrocatalytic properties of LSM-based cathodes for applications in intermediate-temperature SOFCs ͑IT-SOFCs͒, using nanostructur...

Performance and stability of La0.8Sr0.2MnO3 cathode promoted with palladium based catalysts in solid oxide fuel cells

“…The results show that at 800 • C palladium primarily exists in the form of PdO. This is consistent with the observations that the impregnated palladium mainly exists as PdO in the case of Pdimpregnated LSM/YSZ composite cathode calcined at 750 • C [28]. As the temperature increased to 900 • C, metallic palladium species is dominant, however a trace of PdO is also observed.…”

Mn‐Stabilised Microstructure and Performance of Pd‐impregnated YSZ Cathode for Intermediate Temperature Solid Oxide Fuel Cells

“…Also, compared with the conventional LSM-YSZ composite cathode, the Pd-promoted LSM-based cathodes showed significantly improved electrochemical performance with an electrode polarisation resistance of 0.9 X cm 2 at 600°C, which is in contrast to 70 X cm 2 for the conventional LSM-YSZ cathode [14]. However, a significant growth of Pd nanoparticles was observed at 800°C and as such the stability of nanostructured electrodes by impregnation is still a major concern [15].…”

Co2MnO4 spinel-palladium co-infiltrated La0.7Ca0.3Cr0.5Mn0.5O3− cathodes for intermediate temperature solid oxide fuel cells

“…The results also indicate that the electrocatalytic activity of PdO for the O 2 reduction reaction is higher than that of Co 2 MnO 4 spinel phase. The significant performance enhancement with the impregnation of PdO nanoparticles has also been observed on La 0.8 Sr 0.2 MnO 3 cathode [34], La 0.8 Sr 0.2 Co 0.5 Fe 0.5 O 3 cathode [40], Pd + YSZ cathode [44]. The R E value of ∼0.13 cm 2 for the O 2 reduction reaction on PdO-infiltrated LCCM at 800 • C is comparable to ∼0.4 cm 2 at 800 • C reported on GDC-impregnated LCCM cathode [28].…”

“…Solution infiltration is very attractive in the development of nano-structured electrodes that combine the catalytic and electrochemical active phase with the structural rigidity of porous scaffold for IT-SOFCs [31][32][33][34]. It has been shown that the electrocatalytic activity of cathodes for IT-SOFCs can be significantly improved by infiltrating wide range of catalytic active nanoparticles, such as GDC [35,36], La 0.6 Sr 0.4 CoO 3 [37,38], Pd [39,40], (Ba,Sr)(Co,Fe)O 3−ı [41], Sm 0.6 Sr 0.4 CoO 3 [42], and Y 0.5 Bi 1.5 O 3 [43].…”