fig3

Figure 3. (A) XRD patterns of (a) SFM precursor and (b) SFM-R powder and (c) SFM-R-O (O means oxidize) powder and (d) SFM-R-O-R (R means reduce) powder; (B) Cycle number and power density test of SFM at 850 °C under CH₄ and H₂ atmosphere. Reproduced with permission^[19], Copyright 2011, Elsevier; (C) Conductivity changes of SFM synthesized under different conditions (measured in hydrogen and air). Reproduced with permission^[82], Copyright 2016, Elsevier; (D) XRD of (a₁) SFM and (a₂) SF1.5M produced following 5 h calcination in air at 1,000 °C; (a₃) SF1.5M as synthesized after 24 h of treatment at 1,000 °C in H₂ (SFM in the figure means SF1.5M in this review). The EDX analysis of SF1.5M powders is shown in the inset; (E) Redox stability test of SF1.5M. Reproduced with permission^[68], Copyright 2010, Wiley-VCH; (F) 16 cycles of switching the fuel gas between hydrogen, air, and CH₄, the stability of the SF1.5M|LSGM|SF1.5M single cell at 850 °C. Reproduced with permission^[70], Copyright 2011, Elsevier; (G) The occupation of d electrons for Fe in the ideal SF1.5M and SF1.5M with oxygen vacancies; (H) Illustration of SF1.5M’s unusual coordinating environment; (I) Electrochemical performance of SFXM (X = 1, 1.3, 1.5) single cells under a hydrogen atmosphere of 800 °C; (J) Electrochemical performance of SFXM (X = 1, 1.3, 1.5) single cells under a CO₂ atmosphere of 800 °C; (K) O K-edge X-ray absorption spectroscopy of SF1.5M and SFM. Reproduced with permission^[49], Copyright 2021, Wiley-VCH. XRD: X-ray diffraction; SFM: Sr₂FeMoO₆; EDX: energy dispersive X-ray spectroscopy; SFXM: Sr₂Fe_xMo_2-xO₆ (x = 1, 1.3, 1.5).