Exceptionally High Performance Anode Material Based on Lattice Structure Decorated Double Perovskite Sr₂FeMo_2/3Mg_1/3O_6−δ for Solid Oxide Fuel Cells

Abstract

A novel double perovskite Sr2FeMo2/3Mg1/3O6−δ is prepared and characterized as an anode material for solid oxide fuel cells (SOFCs). X‐ray diffraction refinement reveals that Mg and Mo cations locate separately in two different B sites (B and B′ in A2BB′O6) while Fe occupies both B and B′ sites, forming the lattice structure with the form of Sr2(Mg1/3Fe2/3)(Mo2/3Fe1/3)O6−δ. The inactive element Mg doping not only endows the material with excellent redox structural stability but also triggers the creation of antisite defects in the crystal lattice, which provide the material with excellent electrochemical activity. The anode performance of Sr2FeMo2/3Mg1/3O6−δ is characterized in an La0.8Sr0.2Ga0.8Mg0.2O3−δ electrolyte supported cell with La0.58Sr0.4Fe0.8Co0.2O3−δ cathode. A peak power density of 531, 803, 1038, and 1316 mW cm−2 at 750, 800, 850, and 900 °C, respectively, is achieved in humidified H2. The Sr2FeMo2/3Mg1/3O6−δ shows suitable thermal expansion coefficient (16.9(2) × 10−6 K−1), high electrical conductivity, and good tolerance to carbon deposition and sulfur poisoning. First‐principle computations demonstrate that the presence of FeBOFeB′ bonds can promote the easy formation and fast migration of oxygen vacancies in the lattice, which are the key to affecting the anode reaction kinetics. The excellent overall performance of Sr2FeMo2/3Mg1/3O6−δ compound makes it a promising anode material for SOFCs.

Smart Control of Composition for Double Perovskite Electrocatalysts toward Enhanced Oxygen Evolution Reaction

“…[22] Introducing divalent elements (e.g.,N i 2 + ,C u 2 + ,Z n 2 + and Mg 2 + )i nto the B'-site of SFM is effective for tuning the double perovskite structure in an air atmosphere,m ainly owing to the difference in the valence states compared with high valence Mo 6 + (see the Supporting Information, Figure S1). [19,23,24] Here, we show that the substitution of Co for Mo can also stabilize the double perovskite structure in air.B yi ncreasing Co substitution in [25] The XRD peak forS FC0.2MC0.4 at 2q of 19.68 was characteristic of the double perovskite structure (Figure 2a inset). [19,23] The ds pacing was 4.53 ,w hich was calculated by using Bragg'sl aw, nl = 2d sinq,i nw hich l = 0.15406 nm is the wavelength of Cu Ka radiation and 2q = 19.68.A sd epicted in Figure 2b,R ietveld refinement conducted on the XRD data of SFC0.2MC0.4 confirmed its tetragonal structure (I4/m space group) with lattice parameters of a = b = 5.528 and c = 7.850 ,w hich agreed with those of reported B-site ordered double perovskite oxides.…”

“…Sr 2 FeMo 1− x Co x O 6− δ ( x =0.25, 0.30, 0.35, 0.4, and 0.6, denoted as SFMC0.25, SFMC0.3, SFMC0.35, SFMC0.4, and SFMC0.6, respectively), Sr 2 Fe 0.4 Co 0.6 MoO 6− δ (SFC0.6 m ), Sr 2 Fe 0.8 Co 0.2 Mo 0.6 Co 0.4 O 6− δ (SFC0.2MC0.4), Sr 2 FeMo 0.65 Cu 0.35 O 6− δ (SFMCu), Sr 2 FeMo 0.65 Ni 0.35 O 6− δ (SFMNi), Sr 2 FeMo 0.63 Zn 0.37 O 6− δ (SFMZn), Sr 2 FeMo 2/3 Mg 1/3 O 6− δ (SFMMg) and Sr 2 Fe 0.9 Ni 0.1 Mo 0.65 Ni 0.35 O 6− δ (SFNiMNi) were synthesized using a sol‐gel method. A similar synthesis process was reported in our previous research . The powders were obtained by calcining the precursor at 1100 °C (SFMZn, 1150 °C; SFMMg, 1200 °C) in air for 5 h.…”

“…Pure double perovskite Sr 2 FeMoO 6− δ can only be obtained in a reducing atmosphere (e.g., 5 % H 2 /Ar) . Introducing divalent elements (e.g., Ni 2+ , Cu 2+ , Zn 2+ and Mg 2+ ) into the B′‐site of SFM is effective for tuning the double perovskite structure in an air atmosphere, mainly owing to the difference in the valence states compared with high valence Mo 6+ (see the Supporting Information, Figure S1) . Here, we show that the substitution of Co for Mo can also stabilize the double perovskite structure in air.…”

“…[19,23] The ds pacing was 4.53 ,w hich was calculated by using Bragg'sl aw, nl = 2d sinq,i nw hich l = 0.15406 nm is the wavelength of Cu Ka radiation and 2q = 19.68.A sd epicted in Figure 2b,R ietveld refinement conducted on the XRD data of SFC0.2MC0.4 confirmed its tetragonal structure (I4/m space group) with lattice parameters of a = b = 5.528 and c = 7.850 ,w hich agreed with those of reported B-site ordered double perovskite oxides. [19,23,24] X-ray photoelectrons pectroscopy (XPS) was performed to confirmt he existence of the compositionale lements. As shown in Figure S3, Sr (Sr 3d at % 133 eV), Fe (Fe 2p at % 710 eV), Mo (Mo 3d at % 235 eV) and O( O1sa t% 531 eV) were detected for SFM, SFMC0.4 and SFC0.2MC0.4.…”

“…As imilar synthesis process was reported in our previous research. [19,23,24] The powders were obtained by calcining the precursor at 1100 8C( SFMZn, 1150 8C; SFMMg, 1200 8C) in air for 5h.…”