HUANG Yue, MO Yingyu, LIAN Wenchao, QIU Ruiming, LIU Jianping, LEI Libin
(School of Materials and Energy, Guangdong University of Technology, Guangzhou 510006, Guangdong, China)
Abstract: The mixed oxygen ionic-electronic conducting oxides have been widely used in the fields of solid oxide fuel cells SOFCs) and solid oxide electrolysis cells (SOECs). The accurate measurement of ionic transport numbers in the mixed oxygen ionic-electronic conducting oxides is significant for their performance optimization and application. Electromotive force EMF) method is one of the most widely used approaches to measure the ionic transport numbers. However, the easured result of MF method is the apparent ionic transport number (tiapp) . CeO2-based electrolyte was selected as an object, hile a model of defect distribution was established. With this model, the distribution of ionic transport numbers across the CeO2-based electrolyte embrane was analyzed and the effect of test conditions on tiapp was examined by using the EMF method, thus evaluating the accuracy of the EMF method. It is demonstrated that the ionic transport number is inhomogeneous across the electrolyte membrane. tiapp is significantly dependent on thickness of the electrolyte membrane when the electrolyte membrane is elatively thin. When there is a large gradient of oxygen chemical potential on both sides of the electrolyte membrane (POhight 2 / POlow2 ＞1025 ) , tiapp tends to be ionic transport number of the electrolyte layer at high PO2 side and decreases with increasing temperature and the electronic conductivity coefficient of the electrolyte. tiapp tends to be ionic transport number of the electrolyte layer at the low PO2 side when the two sides of the electrolyte layer are in reducing atmospheres(PO2＜10-20atm).tiapp mainly reflects the ionic transport number of the electrolyte layer at the high PO2 side, when PO2 on the two sides of theelectrolyte layer are large (PO2＞10-15atm).
Key words: electromotive force method; solid oxide fuel cells; defect distribution model; mixed oxygen ionic-electronic
conducting oxides; ionic transport number