Synthesis and Evaluation of Ca-doped Sr2Fe1.5Mo0.5O6-δ as Symmetrical Electrodes for High Performance Solid Oxide Fuel Cells

Abstract

A series of Ca-substituted Sr 2 Fe 1.5 Mo 0.5 O 6-δ oxides, Sr 2-x Ca x Fe 1.5 Mo 0.5 O 6-δ (SCFMO, x=0, 0.2, 0.4 and 0.6), were synthesized and evaluated as potential electrodes for symmetrical solid oxide fuel cells. X-ray diffraction examination showed that all samples maintained cubic perovskite structure in both air and wet hydrogen atmospheres. Temperature programmed reduction measurements indicated that the Ca 2+ substitution promoted the catalytic activity of SCFMO toward oxygen evolution reactions. Symmetrical anode fuel cell measurements showed the lowest polarization resistance in humidified hydrogen emerged at x=0.6. Single cells-SC 0.6 FMO|La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3 (LSGM)|SC 0.6 FMO, fabricated via tape-casting and impregnation methods, produced peak power densities of 1.05 W•cm-2 at 800 ℃ and 0.41 W•cm-2 at 650 ℃ when operating on hydrogen fuels and air oxidants. These results demonstrate SC 0.6 FMO is a potential electrode material for symmetrical solid oxide fuel cells.

Recent advances in heteroatom substitution Sr2Fe1.5Mo0.5O6–δ oxide as a more promising electrode material for symmetrical solid-state electrochemical devices: A review

“…Qiao J. et al [80] recorded the onset of SrMoO4 impurity formation starting with calcium doping exceeding x>0.8. The Ca substitution caused a 32.4° [99] and 67.5° [101] peak-shift towards higher angles. This implies that the unit cell shrinks due to the smaller ionic radius of Ca 2+ (0.99 Å) compared to Sr 2+ (1.18 Å), and Pnma space group does not change.…”

“…The space group was identified as Pm-3m in both oxidizing and reducing environments. CaFeO2 could be formed in a hydrogen atmosphere from x=0.2 [101]. Thermal expansion coefficients (TECs) were found to decrease from 16.33×10 -6 K -1 to 15.08×10 -6 K -1 when the Ca-doping increased from 0 to 0.6 [99].…”

“…The interface between the in situ dissolved FeNi3 nanoparticles and the Sr2Fe1.35Mo0.45Ni0.2O6-δ substrate with many oxygen vacancies not only chemically accommodated the CO2 molecules, but also improved the CO2RR efficiency. Cells with the Ni modified ceramic anodes demonstrated relatively good stability in short-term operations when using CH4 as the fuel [101,127,128]. The YSZ-supported electrolyte with (NiFe+SFM)-SDC fuel electrode and LSM-YSZ oxygen electrode showed a significant increase in performance compared to SFM-SDC and other conventional fuel electrodes for direct CO2 electrolysis [129].…”

“…These results may be explained by the changes observed in the redox couples proportion by the conductivity being influenced by the electronic conductivity via the Fe 3+ +Mo 5+ =Fe 2+ +Mo 6+ process. Fuel cell of the symmetrical Sr2-xCaxFe1.5Mo0.5O6-δ electrode performances were measured both in humidified hydrogen fuels and dry air oxidants at a flow rate [101].…”

Nonstoichiometric Strontium Ferromolybdate as an Electrode Material for Solid Oxide Fuel Cells

“…In SF 1.5 M, a cubic structure is preserved by A-site substitution of Sr 2+ by Ba 2+ up to 30% [37] and Sr 2+ by Ca 2+ up to 30% [38], and B-site substitution of Fe 2+ / 3+ by Co 2+ / 3+ up to 33% [39], Fe 2+ /Fe 3+ by Ni 2+ up to 26.6% [40,41], Fe 2+ /Fe 3+ by Nb 4+ /Nb 5+ by 6.7% [30], Fe 2+ /Fe 3+ by Sc 3+ up to 13.3% [42] and Mo 5+ / 6+ by Sn 2+ / 4+ up to 100% [43]. Contrarily, at room temperature, Sr 2−x Ca x Fe 1.5 MoO 6−δ (S 2−x C x FM), x = 0-0.6, [44] and Sr 2 Fe 1.5 Mo 0.5−x Nb x O 6−δ (S 2 F 1.5 M 0.5−x N x ), x = 0-0.2 [45] were assigned to the space group Pnma.…”