Abstract
Perovskite anodes, nowadays, are used in any solid oxide fuel cell (SOFC) instead of conventional nickel/yttria-stabilized zirconia (Ni/YSZ) anodes due to their better redox and electrochemical stability. A few compositions of samarium-substituted strontium titanate perovskite, SmxSr1−xTiO3−δ (x = 0.00, 0.05, 0.10, 0.15, and 0.20), were synthesized via the citrate-nitrate auto-combustion route. The XRD patterns of these compositions confirm that the solid solubility limit of Sm in SrTiO3 is x < 0.15. The X-ray Rietveld refinement for all samples indicated the perovskite cubic structure with a P m 3 ¯ m space group at room temperature. The EDX mapping of the field emission scanning electron microscope (FESEM) micrographs of all compositions depicted a lower oxygen content in the specimens respect to the nominal value. This lower oxygen content in the samples were also confirmed via XPS study. The grain sizes of SmxSr1−xTiO3 samples were found to increase up to x = 0.10 and it decreases for the composition with x > 0.10. The AC conductivity spectra were fitted by Jonscher’s power law in the temperature range of 500–700 °C and scaled with the help of the Ghosh and Summerfield scaling model taking νH and σdc T as the scaling parameters. The scaling behaviour of the samples showed that the conduction mechanism depends on temperature at higher frequencies. Further, a study of the conduction mechanism unveiled that small polaron hopping occurred with the formation of electrons. The electrical conductivity, in the H2 atmosphere, of the Sm0.10Sr0.90TiO3 sample was found to be 2.7 × 10−1 S∙cm−1 at 650 °C, which is the highest among the other compositions. Hence, the composition Sm0.10Sr0.90TiO3 can be considered as a promising material for the application as the anode in SOFCs.
Highlights
Solid oxide fuel cells (SOFC) and solid oxide electrolysis cells (SOEC) are of great interest for their high efficiency of the conversion between chemical energy and electric power without greenhouse gases emissions
The samples Smx Sr1−x TiO3− δ are designated as substituted SrTiO3 (SST) and the compositions with x = 0.00, 0.05, 0.10, 0.15 and 0.20 are assigned as SST0, SST5, SST10, SST15 and SST20, respectively
The tolerance factor according to Goldschmidt relation [27,28] is nearly 1, which shows the formation of ideal perovskite structure
Summary
Solid oxide fuel cells (SOFC) and solid oxide electrolysis cells (SOEC) are of great interest for their high efficiency of the conversion between chemical energy and electric power without greenhouse gases emissions. Their net-zero environmental impact is becoming truly affordable, as demonstrated by the continuous development of the use of bio-fuels and by the production of hydrogen through. SOFCs are more efficient in comparison to a conventional power plant and lower temperature polymer-based fuel cells [9,10]. Electrolyte and electrodes are the essential component of a solid oxide fuel cell. The state of the art material for the electrolyte is fluorite-structured yttria-stabilized zirconia (YSZ) because of its wide range of stability in oxidizing and reducing media [14], doped ceria [15] and perovskite Sr- and Mg-incorporated lanthanum gallate (LSGM) are considered as alternatives for intermediate operative temperatures
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