Alberto Tarancón tells Journal of Materials Chemistry about his hot paper.

1. Could you explain the significance of your article to the non-specialist? 
Lowering the operating temperature of solid oxide fuel cells (SOFCs) to the intermediate temperature range (500- 700 °C) in order to improve materials compatibility and reduce costs has become one of the main SOFC research goals.  This paper presents the suitability of GdBaCo₂O_5+delta, a mixed ionic-electronic conductor, as a cathode for intermediate-temperature SOFCs. Both oxygen transport properties and electrical performance were evaluated obtaining comparable figures to previously reported excellent cathodes. Moreover, its particular structural characteristics suggest a new family of solid oxide fuel cell cathode materials based on layered perovskites.

2. What has motivated you to conduct this work? 
Many simple perovskite-type mixed ionic-electronic conductors have been extensively studied as possible cathodes in SOFCs, however not much attention has been paid to the perovskite related structures such as the double or layered perovskites. Recent studies suggest for this compound both good electronic conductivity and oxygen transport properties at high temperatures. Therefore, the accurate study of fundamental and in-use properties was an important issue to cover.

3. Where do you see this work developing in the future? 
Layered perovskites materials open fresh perspectives for cathode development in the field of solid oxide fuel cells of intermediate temperature. The cathode performance is probably the limiting factor when lowering the temperature in SOFC. This is due to the high activation energy for the oxygen reduction reaction usually presented. This compound, and hopefully the whole family, can help to overcome this drawback.

4. Are there any particular challenges facing future research in this area? 
Further investigations are required in order to determine the effect of the layered structure on the electrochemical performance observed, in particular the effect on the low activation energy for oxygen exchange and diffusion, as well as the possibility of improving the polarization resistance by introducing functionally graded materials.

Alberto Tarancón received his Diploma in Physics from the University of Barcelona, Spain, in 2001. From 2002 to 2007 he was involved in his Ph.D. on the "Strategies for Lowering the Temperature in Solid Oxide Fuel Cells" at the Electronics Department of the University of Barcelona. He is currently an Assistant Professor in the same department. In 2007 he completed his degree in Materials Engineering at the Technical University of Catalonia, Spain. His research interests centre on computer simulations of oxide-ionic conductors, impedance spectroscopy of mixed ionic-electronic conductors and technological aspects of Solid Oxide Fuel Cells.