Performance Optimization of Cermet SOFC Anodes: An Evaluation of Nanostructured NiO
The present work is centered on the analysis of key relationships between the morphology of initial NiO powders used to form Ni-containing cermets and overall quality of the composite SOFC anodes. The commercial Nickel (II) oxide nanopowder (99.8% purity, Sigma-Aldrich) was employed as a model starting material for these studies.
A large series of NiO powders were prepared by annealing of initial NiO at different temperatures (RT-1100 oC). Scanning and transmission microscopy, X-ray diffraction, thermogravimetry, X-ray photoelectron and Raman spectroscopic analyses were employed for morphological, chemical and structural characterization. Then the powders were mixed with highly dispersed solid electrolyte of 10 mol.% Sc2O3 and 1% mol.% CeO2 stabilized zirconia (10Sc1CeSZ) and an organic solvent to obtain screen-printable pastes, used to deposit anode layers onto 10 mol.% Sc2O3 and 1% mol.% Y2O3 stabilized ZrO2 membranes for further microstructural and electrochemical studies. The results showed, in particular, that starting NiO nanopowder (Fig. 1) possesses a core-shell structure, with the crystalline core covered by amorphous shell rich of excessive oxygen and adsorbed water. These surface layers, having critical impact on the integrity and performance of resultant anodes, can be eliminated by thermal pre-treatment.