Bismuth and niobium co-doped barium cobalt oxide as a promising cathode material for intermediate temperature solid oxide fuel cells

Significance Statement

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. 

Bismuth and niobium co-doped barium cobalt oxide as a promising cathode material for intermediate temperature solid oxide fuel cells Renewable Energy Global Innovations

About the author

Shaofei He received his bachelor degree in “Physical Chemistry” at Harbin Institute of Technology in 2013 in Dr. Sun group, He then went on his study and received his master degree in physical chemistry in 2015. His research is focused on developing novel cathode for solid oxide fuel cells, including the electrochemical performance and the transfer phenomenon and mechanism of the electrochemical conversion.  

About the author

Shiru Le is currently an Associate Professor in “Institute of Chemistry and Energy Materials Innovation ” at Harbin Institute of Technology.He received his PhD(2005) in “Chemical Engineering and Technology” at Harbin Institute of Technology.  Then he was an Assistant Professor in Harbin Institute of Technology. In 2013, he was promoted as an Associate Professor in Harbin Institute of Technology. His research is focused on solid oxide fuel cell, including developing novel electrolyte and cathode with high performance, and the transfer phenomenon and mechanism of electrochemical conversion.  

About the author

Lili Guan received her bachelor degree in Applied Chemistry at Yanshan University in 2008 and her master degree in Inorganic chemistry at Harbin Institute of Technology in 2010, now she is an Ph.D. candidate in “Chemical Engineering and Technology” at Harbin Institute of Technology. Hers research  is focused on solid oxide fuel cell, including study sintering process and ionic transport mechanism of novel electrolyte.

About the author

Tao Liu received his bachelor degree in “Applied Chemistry” at Harbin Engineering University in 2013, then he moved to Harbin Institute of Technology and joined Dr. Sun group and received his master degree in “ Chemical Engineering and Technology” in 2015, now he is an engineer in Xinbang Industrial at Huizhou City in China.

About the author

Kening Sun is currently a Full Professor in “Institute for Chemistry and Energy Materials Innovation” at Harbin Institute of Technology. Dr. Kening Sun received his PhD degree in 1996, then he spent 1 year as a research fellow in Surface Chemistry National Laboratory at Universit Pierre et Marie Curie. He received the Yangtse River Scholar in 2005. His research interests is the interdisciplinary science for energy conversion, clean environmental chemistry. He has won National Invention Award Four and 2nd Prize of National Sci-Tech Advanced Award.  

Journal Reference

Journal of Power Sources,Volume 295, 2015, Pages 33–40.

Shaofei He1, Shiru Le2, Lili Guan1, Tao Liu1, Kening Sun2

Show Affiliations
  1. Department of Chemistry, School of Science, Harbin Institute of Technology, NO. 92 Xidazhi Street, Harbin, 150001, PR China
  2. Academy of Fundamental and Interdisciplinary Sciences, Harbin Institute of Technology, NO. 2 Yikuang Street, Harbin 150080, PR China

Abstract

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.

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