Functionally graded composite La2NiO4+δ and La4Ni3O10-δ solid oxide fuel cell cathodes

Functionally graded electrodes have been fabricated from members of the (LaNiO3)(n)LaO Ruddlesden-Popper family. These consist of a thin compact layer of La2NiO4 (+) (delta) deposited on the electrolyte, topped by a thicker porous La2NiO4 (+) (delta) + La4Ni310 - delta composite layer, completed by a thin porous La4Ni3O10 - delta layer acting as a current collector. The microstructure and electrochemical role of these layers are discussed in detail. It was found that using a 50:50 wt.% mix in the composite layer gave the best performance; ASRs at 500, 550, 600, 650, and 700 degrees C were 15.6, 5.53, 2.29, 1.06 and 0.53 Omega cm(2) respectively. This represents high performance for this class of material, particularly notable at the lower-end of the temperature range. As such this grading process is an attractive proposition for further research towards lowering the operating temperature of SOFCs. (C) 2013 Elsevier B.V. All rights reserved.