A clean energy conversion technology with higher efficiency is attractive to reduce the carbon dioxide production, sulfur pollution. Solid oxide fuel cells (SOFCs) are highly efficient and environmentally friendly devices to convert chemical energy in fuels directly to electrical power as compared to traditional thermal power generation plants.The key to develop low and intermediate solid oxide fuel cell is cathode with high performance .
BaCoO3 is a promising parent component as Ba’s ionic radius (1.60 Å) is large,which is beneficial to create large free volume and sufficient oxygen vacancy for oxygen ions transportation in the bulk, together with the low binding energy of Ba-O enhancing the fast oxygen diffusion in the bulk and the quick oxygen exchange over the surface. Bi doping is attractive as its small binding energy of Bi-O bond. Nb doping can stabilize the BaCoO3 cubic perovskite structure from room temperature to about 1000 ℃.Further, a small amount of Nb doping further enhanced the electrochemical activity.
Our team found that The Nb doping content at B-site had a significant effect on crystal structure, oxygen vacancy concentration, electrical conductivity, thermal expansion behavior and electrochemical performance. The cubic perovskite structure was stabilized to room temperature for BBCNy oxides with Nb doping content of 0.10. The Rp for BBCNd with Nd doping content of 0.15 is only 0.079Ω·cm2 at 700 ℃. The Rtotal of the single-cells (Ni-YSZ|YSZ|GDC|BBCNd0.15) is 0.567, 0.361 and 0.213Ω·cm2 at 650, 700 and 750 ℃,respectively, together with the maximum power density of 1.23 W·cm2 at 750 ℃. These results are very promising for low and intermediate temperature solid oxide fuel cell.
Shaofei He1, Shiru Le2, Lili Guan1, Tao Liu1, Kening Sun2Show Affiliations
- Department of Chemistry, School of Science, Harbin Institute of Technology, NO. 92 Xidazhi Street, Harbin, 150001, PR China
- Academy of Fundamental and Interdisciplinary Sciences, Harbin Institute of Technology, NO. 2 Yikuang Street, Harbin 150080, PR China
Perovskite oxides BaBi0.05Co0.95−yNbyO3−δ (BBCNy, 0 ≤ y ≤ 0.2) are synthesized and evaluated as potential cathode materials for intermediate temperature solid oxide fuel cells (IT-SOFCs). Highly charged Nb5+ successfully stabilizes the cubic perovskite structure to room temperature with Nb substituting content y ≥ 0.1. The phase structure, thermal expansion behavior, electrical conductivity and electrochemical performance of BBCNy with cubic phase are systematically studied. The samples exhibit excellent chemical compatibility with GDC and have sufficiently high electrical conductivities. However, the thermal expansion coefficients of BBCNy samples are nearly twice those of the most commonly used electrolyte materials YSZ and GDC, which is a major drawback for application in IT-SOFCs. The polarization resistances of BBCNy with y = 0.10, 0.15 and 0.20 on GDC electrolyte are 0.086, 0.079 and 0.107 Ω cm2 at 700 °C, respectively. Even though the YSZ electrolyte membrane and GDC barrier layer are approximately 50 μm and 10 μm in thickness, the highest maximum power density (1.23 W cm−2) of the single cell Ni-YSZ|YSZ|GDC|BBCN0.15 is obtained at 750 °C. Good long-term stability of the single cell with BBCN0.15 cathode is also demonstrated. These results demonstrate that BBCNy perovskite oxides with cubic structure are very promising cathode materials for IT-SOFCs.Go To Journal of Power Sources