Detailed impedance characterization of a well performing and durable Ni:CGO infiltrated cermet anode for metal-supported solid oxide fuel cells

Further knowledge of the novel, well performing and durable Ni:CGO infiltrated cermet anode for metal supported fuel cells has been acquired by means of a detailed impedance spectroscopy study. The anode impedance was shown to consist of three arcs. Porous electrode theory (PET) represented as a transmission line response could account for the intermediate frequency arc. The PET model enabled a detailed insight into the effect of adding minor amounts of Ni into the infiltrated CGO and allowed an estimation of important characteristics such as the electrochemical utilization thickness of the anode. Furthermore, the study also revealed that the observed high frequency impedance arc cannot solely be a consequence of the grain boundaries within the electrolyte as previous studies have assumed. Instead, the results pointed towards an oxide ion charge transfer resistance between the electrolyte and the infiltrated anode. The low frequency impedance arc was in accordance with previous studies interpreted to be associated with the gas concentration. Finally, the robustness of the infiltration towards sintering and/or agglomeration at elevated temperature was studied. The results showed that the performance of the infiltrated submicron sized particles was surprisingly robust. TEM analysis revealed the nano sized Ni particles to be trapped within the CGO matrix, which along the self limiting grain growth of the CGO seem to be able to stabilize the submicron structured anode. (C) 2012 Elsevier B.V. All rights reserved.