Novel Gradient-Porosity Structure Cathode for Intermediate-Temperature Solid Oxide Fuel Cells

Abstract

A-site cation ordered double perovskite cathode, especially LnBaCo2O5+δ series, have drawn great interests due to their faster oxygen ion diffusion and higher electrical conductivity[1-3].As a promising SOFC cathode with highest oxygen diffussion coefficient (D*) among the mixed ionic and electronic conductor (MIEC)[4], PrBaCo2O5+ δ exhibits great oxygen reduction reaction(ORR) catalytic activity and electrochemical performance[5] .Here we proposed a gradient-porosity PrBaCo2O5+ δ SOFC cathode. The top-layer of the cathode was highly porous while the sub-layer much denser. Gases’ adsorption plays important roles in ORR process, thus pores’ distribution has great influence on cathode’s performance[6]. Higher porosity means more ORR active regions but less ions paths, and vice versa. There is a trade-off between gases path and ions path. And gradient-porosity cathode aiming at increasing gases adsorption region at gas-contacted surface of cathode about 3-5um depth, at the meantime ensure ions’ fast transfer by enlarge cathode-electrolyte contacted regions. This targeted modification will enhanced cathode’s ORR activity and can be adopted in SOFC’s practical application. [1] Q. Zhou, T. He, Y. Ji, J. Power Sources, 185,754-758 (2008) .[2] A. Chang, S.J. Skinner, J.A. Kilner, Solid State Ion, 177,2009-2011 (2006) .[3] S. Choi, S. Yoo, J. Kim, S. Park, A. Jun, S. Sengodan, J. Kim, J. Shin, H.Y. Jeong, Y. Choi, Sci. Rep, 3 (2013).[4] A. Tarancón, M. Burriel, J. Santiso, S.J. Skinner, J.A. Kilner, J. Mater. Chem, 20,3799-3813 (2010) .[5] D. Chen, R. Ran, K. Zhang, J. Wang, Z. Shao, J. Power Sources, 188,96-105 (2009) .[6] S. Skinner, J. Kilner, Solid State Ion, 135,709-712 (2000) .