Han Xu

Department of Building Environment and Energy Engineering, Xi’an Jiaotong University, Xi’an, China

School of the Built Environment and Architecture

Email: xuhanxh@xjtu.edu.cn

Bio

Dr. Han XU is an associate professor in Building Environment and Energy Engineering at Xi’an Jiaotong University. She received the B.Eng. degree in Building Environment and Energy Engineering from Xi’an Jiaotong University in 2008 and the Ph.D. degree in Power Engineering and Engineering Thermophysics from Xi’an Jiaotong University in 2015. She was a visiting scholar in School of Materials Science and Engineering of Georgia Institute of Technology from 2016 to 2017. Her research interests include the transport and reactions in multi-scale porous medias, especially in solid oxide fuel cells, distributed energy systems, district heating, smart energy systems, etc.

Title

Solid oxide fuel cell, space charge layer, oxygen vacancy transport, three phase boundary

Abstract

The nanocomposite electrode is a promising technology to improve the electrochemical performance of intermediate/low temperature solid oxide fuel cells (SOFCs). Within the nanocomposite electrode, the space charge layer (SCL) effect is likely to alternate the oxygen vacancy transport adjacent to the three phase boundaries (TPBs), which is one of the key factors to improve the electrochemical performance of the electrodes. Existing studies usually adopt Poisson-Boltzmann (PB) equation to predict the SCL effect, in which all the charge carriers are assumed to be in the electrochemical equilibrium state and the net current of the conductor is nearly zero. Apparently, the PB equation is uncapable of predicting the SCL effects under typical SOFC operating conditions, since the net current is obviously not zero. In this study, based on the patterned electrode, we develop a numerical methodology via coupling the Poisson equation and mass conservation equation of charge carriers for the oxygen vacancy transport with considering the SCL effect under SOFC operating conditions. Our results show that an obvious gradient is observed in the oxygen vacancy concentration near the TPBs due to the SCL effect, which leads to a remarkable diffusion current that is even larger than the migration current driven by the potential gradient. The SCL resistance is computed to quantitatively characterize the influence of the SCL effect on the oxygen vacancy transport. The SCL resistance shows a decreasing tendency with increasing the dimensionless Debye length and dimensionless potential, but it increases with increasing the dimensionless average current density. These results and the numerical methodology could be helpful for improving the performance of intermediate/low temperature SOFCs via rationally designing robust nanocomposite electrodes.