Unraveling the problem associated with multi-cation oxide formation using urea based infiltration techniques for SOFC application

Abstract

Urea infiltration is the most extensively and ubiquitous method for depositing the multi-cation oxide catalyst layer on the electrode backbone in the SOFC area. The stoichiometry and composition are the two vital parameters for deposited multi-cation oxide nanocatalyst layer on which the catalytic activity and selectivity depend. However, the understanding behind the mechanism of multi-cation oxide nanocatalyst by urea infiltration is still missing, which restricts the reproducibility of this infiltration approach. The infiltration technique of Sm0.5Sr0.5CoO3-δ (SSC) nanoparticle by urea method is highly irreproducible due to the intermediate phase’s formation. This may result from the varying cation stoichiometry being formed along with the final product, and it is assumed to arise mainly due to the difference in precipitation tendency of cations present in the urea precursor solution. We investigate the influence of variation in the urea concentration effect on the stoichiometry of SSC nanoparticles. The difference in several parameters, such as electronegativity, ionic potential, cationic charge, and hydroxylation tendency, brings a competitive reaction within the three cations inside the urea infiltrated precursor solution. Thus, a different instrumental analysis was used to interpret the internal composition and heterostructure of the SSC nanoparticles. By applying, transmission electron microscopy with X-ray powder diffraction, the crystal structure of synthesized SSC nanoparticle was confirmed with the appropriate stoichiometry, and a comprehensive understanding of the mechanism was done for further improving the present urea syntheses protocol with proper reproducibility.