Standard Article

Impact of impurities on reliability of materials in solid oxide fuel cell (SOFC) stack/modules

Advances in Electrocatalysis, Materials, Diagnostics and Durability

Performance degradation

High-temperature fuel cells

  1. H. Yokokawa,
  2. N. Sakai,
  3. T. Horita,
  4. K. Yamaji

Published Online: 15 DEC 2010

DOI: 10.1002/9780470974001.f500065

Handbook of Fuel Cells

Handbook of Fuel Cells

How to Cite

Yokokawa, H., Sakai, N., Horita, T. and Yamaji, K. 2010. Impact of impurities on reliability of materials in solid oxide fuel cell (SOFC) stack/modules. Handbook of Fuel Cells. .

Author Information

  1. National Institute of Advanced Industrial Science and Technology (AIST), Ibaraki, Japan

Publication History

  1. Published Online: 15 DEC 2010

Abstract

The impurity behavior in solid oxide fuel cells is discussed in terms of the thermodynamic characteristic properties in particular on the basis of acid–base concept in theoretical consideration and in terms of actually observed quantities of impurities with SIMS techniques. The thermochemical stability of cathodes can be represented in the chemical potential diagrams where the thermodynamic activity of basic oxides (SrO, La2O3) are used. By adopting the same axes, this makes it possible to compare thermodynamic properties for different elements in the La–Sr–M–O system (M = elements). By using this diagram, the acidity of respective impurity elements are defined and compared with the main transition metal element in cathode materials. The impurity behavior inside SOFC stacks is also examined by using the diagram with temperature and oxygen potential axes. This makes it possible to see the interaction of the cell component with impurities as functions of temperature and oxygen potentials. Examples are given for Ni–S–O–H system. Finally, the impurity behavior in actual stacks detected by SIMS was examined and compared with thermodynamic prediction with the emphasis on the interaction between impurities and the main component as functions of fuel utilization and other fuel cell conditions.

Keywords:

  • thermodynamic properties;
  • thermodynamic diagram;
  • impurity;
  • acid–base relation;
  • volatile species;
  • reactivity;
  • cathodes;
  • Ni anode;
  • Ni–S interaction;
  • SIMS