Tailoring Sr2Fe1.5Mo0.5O6−δ with Sc as a new single-phase cathode for proton-conducting solid oxide fuel cells

Abstract

Sc-doped Sr 2 Fe 1.5 Mo 0.5 O 6−δ (SFMSc) was successfully synthesized by partially substituting Mo in Sr 2 Fe 1.5 -Mo 0.5 O 6−δ (SFM) with Sc, resulting in a higher proton diffusion rate in the resultant SFMSc sample. Theoretical calculations showed that doping Sc into SFM lowered the oxygen vacancy formation energy, reduced the energy barrier for proton migration in the oxide, and increased the catalytic activity for oxygen reduction reaction. Next, a proton-conducting solid oxide fuel cell (H-SOFC) with a single-phase SFMSc cathode demonstrated significantly higher cell performance than that of cell based on an Sc-free SFM cathode, achieving 1258 mW cm −2 at 700°C. The performance also outperformed that of many other H-SOFCs based on single-phase cobalt-free cathodes. Furthermore, no trade-off between fuel cell performance and material stability was observed. The SFMSc material demonstrated good stability in both the CO 2 -containing atmosphere and the fuel cell application. The combination of high performance and outstanding stability suggests that SFMSc is an excellent cathode material for H-SOFCs.

Tailoring cobalt‐free La0.5Sr0.5FeO3‐δ cathode with a nonmetal cation‐doping strategy for high‐performance proton‐conducting solid oxide fuel cells

“…One is at the Fe site next to the P cation (Fe–P site), and the other is at the Fe site far from the P cation (Fe–Fe site), as shown in Figure S4. The O 2 adsorption energies were calculated at 0.27 and 0.52 eV on the Fe–P and Fe–Fe sites, respectively, implying O 2 adsorption on the Fe–P site is more favorable at the LSFP surface due to the lower energy 44–46 . The analysis of the charge density difference (Figure 2C) revealed that the P‐doping into LSF evidently changes the electronic structure of the Fe ions next to the P cation (Fe–P site), leading to a charge depletion for the Fe ions.…”

“…The O 2 adsorption energies were calculated at 0.27 and 0.52 eV on the Fe-P and Fe-Fe sites, respectively, implying O 2 adsorption on the Fe-P site is more favorable at the LSFP surface due to the lower energy. [44][45][46] The analysis of the charge density difference (Figure 2C) revealed that the P-doping into LSF evidently changes the electronic structure of the Fe ions next to the P cation (Fe-P site), leading to a charge depletion for the Fe ions. The charge depletion could result in the increase of the Fe valence (loss of electrons).…”

Enhancing the oxygen reduction reaction activity and durability of a double-perovskite via an A-site tuning

“…The peak at around 531.8 eV is attributed to hydroxyl groups or carbonate adsorbed on the surface. The result manifests that a high amount of oxygen vacancies has been likely produced (O ads /O lat = 1.86), which is expected to accelerate the transport of oxygen ions and improve the ORR activity of the cathode [2,32].…”

“…The peaks of 779.7 and 795.0 eV are assigned to Ba 2+ in the perovskite or the surface carbonate [34]. Two sets of peaks belonging to Co 4+ (2p 3/2 at around 781.3 eV and 2p 1/2 at around 797.0 eV) and Co 3+ (2p 3/2 at around 777.8 eV and 2p 1/2 at around 793.0 eV) are obtained by deconvolution [31][32][33][34][35][36]. Two weak satellite peaks are attributed to Co 3 O 4 (a mixed state of Co 2+ and Co 3+ ), indicating a small amount of Co 2+ is on the surface of the BGPC sample [37,38].…”

BaTb0.3Fe0.7O3−δ: a new proton-conductor-derived cathode for proton-conducting solid oxide fuel cells

“…35–37 However, single-phase cathodes with triple-conduction, namely oxygen-ion conduction, proton-conduction, and electron-conduction, have been proposed in recent years and are claimed to extend TPBs to the whole cathode surface and thus improve the cathode performance. 38–40 It is known that many triple-conduction cathodes are derived from proton-conducting oxides. 41 This design is reasonable based on the consideration that the proton-conducting oxide as the parent compound can maintain some proton conduction for the derived cathode, and the addition of transition metals into the proton-conducting oxide can introduce electronic conduction and catalytic activity.…”