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[Display omitted] • Fe–Ni decorated LaSr(Fe,Mo)O 4 (R–LSFMN x) were obtained by in–situ reducing LSFMN x. • R–LSFMN x were used as anodes of SOFCs with H 2 , CO, and syngas as fuels. • R–LSFMN0.07 anode exhibits the optimal electrochemical performance and stability. • Effects of Ni level in Fe–Ni on anode performance and stability were investigated. • Effect of Ni level in Fe–Ni on anode electrochemical dynamics was investigated. Fe–Ni nanoparticle–decorated LaSr(Fe,Mo)O 4 Ruddlesden–Popper (R–P) perovskite anodes, named R–LSFMN x , were prepared in situ by reducing perovskites La 0.5 Sr 0.5 Fe 0.9 Mo 0.1– x Ni x O 3– δ (LSFMN x ; x = 0.03–0.07) under SOFC anode operating conditions. Electrolyte–supported single cells with a configuration of R–LSFMN x |La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3– δ (LSGM)|Ba 0.5 Sr 0.5 Co 0.9 Nb 0.1 O 3– δ were used to evaluate the electrochemical performances and redox/long–term stability of the R–LSFMN x anodes fuelled by H 2 , CO, and simulated syngases (x % H 2 /CO; x = 50–10). EIS analyses indicated that the increased Ni level in the exsolved Fe–Ni nanocatalysts significantly promotes fuel diffusion/adsorption/dissociation, which plays a rate–limiting role in the anode fuel oxidation. Furthermore, the incremental Ni in Fe–Ni alloy also enhances the anode redox/long–term stability and carbon resistance/tolerance, and the R–LSFMN0.07 anode, i.e. , Ni level in Fe–Ni alloy attaining ∼14 mol.%, displays the optimal stability and carbon resistance/tolerance. Finally, the potential of the R–LSFMN0.07 anode for direct utilization of syngas was demonstrated by the characterization of the electrochemical performance and stability based on the R–LSFMN0.07 anode cell. [ABSTRACT FROM AUTHOR]

Sr–deficient Sr 2– x MgMoO 6– δ (SMM x) (x = 0.00–0.25) double perovskites were prepared using the sol–gel process. XRD results indicate that the x = 0.00–0.15 samples are pure phases with good redox stability, while trace SrMoO 4 impurity was detected for the samples with x ≥ 0.20. XPS analysis demonstrates that Mo5+ content increases monotonously with Sr–deficiency, and the increasing number of Mo5+/Mo6+ redox pairs enhances electrical conductivity with increasing x. Among the SMM x compositions, the SMM0.15 anode exhibits optimal electrochemical performance, with polarization resistance attaining a minimum of 0.36 and 0.59 Ω cm2 in H 2 and CO, respectively, at 850 °C. Using SMM0.15 as the anode skeleton, Cu nanoparticles were loaded onto the skeleton surface via nitrate impregnation. The resulting Cu–impregnated SMM0.15 composite anodes exhibited significantly improved electrical and electrochemical properties. Peak power densities of a single cell supported by a 300–μm–thick La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3– δ electrolyte and a twice Cu–impregnated SMM0.15 composite anode achieve 933 mW cm−2 in H 2 and 415 mW cm−2 in CO at 850 °C. The electrochemical reactions at the anode were mainly dominated by fuel diffusion and adsorption/disassociation, particularly for CO. The good cell stability in both H 2 and CO further demonstrates that Cu–impregnated SMM0.15 has great potential as an anode candidate for SOFCs. [ABSTRACT FROM AUTHOR]

Pr-deficient Pr 1− x BaCo 2 O 5+ δ (P 1− x BCO) oxides are evaluated as cathode materials for intermediate temperature solid oxide fuel cells (IT-SOFCs). Effects of Pr-deficiency on electrical conductivity, thermal expansion and electrochemical properties are investigated. Both the conductivity and thermal expansion coefficient (TEC) decrease with increasing Pr-deficiency. All of the conductivity, thermal expansion and TGA measurements demonstrate the existence of high temperature order-disorder transition. The oxygen reduction mechanism for P 1− x BCO cathodes are characterized by electrochemical impedance spectroscopy. Over the temperature range of 600−800 °C, the cathode polarization resistance is mainly contributed from electronic charge transfer over the cathode surface. Proper Pr-deficiency reduces cathode polarization resistance ( R p ), and the lowest R p (0.081 Ω cm 2 at 700 °C) is obtained for the P 0.92 BCO cathode. In addition, the effects of order-disorder transition on the properties of P 1− x BCO cathodes have also been discussed. Maximum power densities of a single-cell with P 0.92 BCO cathode on 300-μm thick Sm 0.2 Ce 0.8 O 1.9 (SDC) electrolyte achieve 446–987 mW cm −2 at 650–800 °C. These results suggest that, among various P 1− x BCO oxides, P 0.92 BCO is the most promising candidate cathode material for IT-SOFCs. [ABSTRACT FROM AUTHOR]

Perovskite oxide SrFe 0.9 Mo 0.1 O 3− δ (SFM) was evaluated as the electrode for symmetric solid oxide fuel cells (S–SOFCs) with Sm 0.2 Ce 0.8 O 2− δ (SDC) and La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3− δ (LSGM) electrolytes. Under reducing conditions at 800 °C, the SFM was reduced to be a multi-phase composite consisting of the single perovskite phase, Ruddlesden–Popper (RP) layered perovskite phase, and Fe0 phase. After reoxidation at 800 °C in air, this multi−phase system was again transformed into the parent perovskite phase again, indicating good redox reversibility of the SFM. At 700 °C, polarisation resistances of the SFM used as the cathodes on the LSGM and SDC electrolytes were 0.28 and 0.14 Ω cm2, respectively, in air. Using H 2 as a fuel, the LSGM and SDC supported S–SOFCs with the SFM symmetric electrodes showed the peak power outputs of 253 and 269 mW cm−2, respectively, at 700 °C. Finally, the good long-term stability and redox-cycling stability of the S–SOFCs further demonstrate the potential of the SFM as the symmetric electrode. • SFM was first evaluated as symmetric electrode of S–SOFC. • SFM electrode shows good redox reversibility under IT-SOFC operating temperatures. • Reduced-reoxidised SFM exhibits a porous surface structure. • SFM symmetric electrode exhibits excellent electrochemical performances. • S–SOFC with SFM electrode exhibits good long-term stability and redox stability. [ABSTRACT FROM AUTHOR]

• LBFMo was evaluated as electrode of symmetric SOFC (S-SOFC). • Ba and Mo co-doping succeeds in stabilizing the cubic structure of the LaFeO3-δ phase. • Excellent electrochemical performance for the S-SOFC with LBFMo electrode was obtained. • Good stability for the S-SOFC with LBFMo electrode was determined. Cobalt − free perovskite oxide La 0.5 Ba 0.5 Fe 0.95 Mo 0.05 O 3− δ (LBFMo) was investigated as the electrode of symmetric solid oxide fuel cell (S − SOFC) based on 300−um − thick La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3− δ (LSGM) electrolyte. The electrochemical performance of the S − SOFC with LBFMo|LSGM|LBFMo configuration was evaluated using ambient air as oxidant and H 2 as fuel. The maximum power density (P max) of the S − SOFC achieves as high as 0.96 W cm−2 at 800 °C; meanwhile, the total polarization resistance (R pt) of the S − SOFC (including the contributions of both cathode and anode) is only ∼0.12 Ω cm2. Impedance spectra analysis indicates the polarization associated with anode plays a more rate − limiting role in the whole electrochemical reaction process of the S − SOFC. In addition, using LBFMo as symmetric electrode, the S − SOFC also exhibits good cell stability. All results indicate that the LBFMo is a very potential candidate for S − SOFC electrode. [ABSTRACT FROM AUTHOR]

Perovskite oxides La x Sr 1–x Co 0.9 Sb 0.1 O 3– δ (LSCSbx, x=0.0–0.8) are investigated as IT–SOFC cathodes supported with La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3– δ (LSGM) electrolyte. All LSCSbx oxides have a tetragonal distorted perovskite structure with s.g. P4/mmm , while a La 2 Co 2 O 5 impurity phase was observed within La doping levels at x=0.6–0.8. The LSCSb0.4 has a good chemical compatibility with LSGM electrolyte for temperatures up to 1050 °C. XPS examinations indicate the existence of Co 3+ /Co 4+ mixed valence states in LSCSbx. The conductivity increases with La doping and the LSCSbx with x=0.4 exhibits the highest electrical conductivity (e.g., 673–1637 S cm −1 at 300–850 °C). The thermal expansion coefficient (TEC) decreases from 25.89×10 –6 K –1 for x=0.0 to 18.5×10 –6 K –1 for x=0.6 at 30–900 °C. Among the LSCSbx compositions, the LSCSb0.2 exhibits the lowest polarization resistance ( R p ), which is merely 0.069 Ω cm 2 at 700 °C. The maximum power density of the cell with LSCSb0.2 cathode on 300 µm thick LSGM electrolyte attains 564 mW cm –2 at 850 °C, which is higher than that of SrCo 0.9 Sb 0.1 O 3– δ (SCSb) cathode. All of the results indicate that LSCSb0.2 is a promising material for application in IT–SOFCs cathodes. [ABSTRACT FROM AUTHOR]

Ba x Sr 1− x Co 0.9 Sb 0.1 O 3− δ (BSCSbx, x = 0.0–0.8) are investigated as cathodes for intermediate temperature solid oxide fuel cells (IT-SOFCs). BSCSbx oxides are crystallized in a tetragonal structure with s.g. P4/mmm . XPS analysis shows that Ba doping reduces valence state of Co ions: Co in SrCo 0.9 Sb 0.1 O 3− δ is prone to Co 4+ , while Co in Ba doped SrCo 0.9 Sb 0.1 O 3− δ becomes more prone to Co 3+ . Oxygen deficiency δ increases with Ba doping even at high temperatures. Conductivity is found to decrease with Ba doping. Thermal expansion coefficient (TEC) decreases from 20.6 × 10 −6 K −1 for x = 0.0 to 18.4 × 10 −6 K −1 for x = 0.6 at 30–1000 °C. With increasing x from 0.0 to 0.6, polarization resistance ( R p ) decreases monotonously, and then increases with further increasing x. The lowest R p of 0.081 Ω cm 2 at 700 °C is obtained for BSCSb0.6 cathode. At 700–850 °C, the R p of BSCSb0.6 is mainly contributed from electron charge transfer; however, below 700 °C, ion charge transfer plays a more important role in R p . Maximum power densities of the cell with BSCSb0.6 cathode on 300-μm thick La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3− δ (LSGM) electrolyte attain 306–944 mW cm −2 at 700–850 °C. These results indicate that BSCSb0.6 is a promising cathode for application in IT-SOFC. [ABSTRACT FROM AUTHOR]

Ba0.6Sr0.4Co0.9Nb0.1O3−δ (BSCN)–xGd0.1Ce0.9O1.95 (GDC) composites with various GDC contents (x = 0–40, wt%) have been investigated for their potential application in IT-SOFCs. The effects of GDC addition on thermal expansion and electrochemical performances were studied. Thermal expansion measurement indicates that thermal expansion coefficients (TECs) decrease with increasing GDC content; in addition, GDC plays a catalytic role during the process of low-temperature thermal-driven reduction of Co4+ to Co3+. Polarization resistance (R p) measurement indicates that the proper addition of GDC improves electrochemical performance of BSCN cathode. The optimum GDC addition to BSCN cathode is 20 wt% with the lowest R p of 0.042 Ω cm2 at 700 °C. The maximum power density of a cell with BSCN–20GDC cathode on 300 μm-thick GDC electrolyte achieves 460–880 mW cm−2 at 700–800 °C. The excellent electrochemical performance of BSCN–20GDC composite cathode is ascribed to its much finer microstructure and larger cathode/electrolyte/gas triple phase boundary (TPB) areas. [ABSTRACT FROM AUTHOR]

PrBaCo 2– x Mo x O 5+ δ (PrBCM– x , x = 0.00–0.07) layered perovskites were evaluated as cathodes for IT–SOFCs. The Mo solid solution limit for PrBCM– x was up to x = 0.05. Mo doping in the PrBCM– x decreased the electrical conductivity, which may mainly be due to the disturbed ···Co–O–Co··· electron transport channels with Mo doping. The thermal expansion coefficients decreased from 21.0 × 10−6 K−1 at x = 0.00 to 19.0 × 10−6 K−1 at x = 0.03 and then to 18.1 × 10−6 K−1 at x = 0.05. Although a reduction in electrochemical performance with high–valence Mo doping into PrBaCo 2 O 5+ δ (PrBCO) was demonstrated, the reduced TECs and improved electrochemical stability were more attractive for the application of SOFC cathode. Electrochemical dynamic processes determined by EIS fitting indicated that Mo doping contributed to the rate–determining role of ion charge transfer in the oxygen reduction reaction and thus resulted in reduced electrochemical performance. By comprehensive consideration, the PrBCM–0.03 was confirmed as the most suitable cathode candidate for IT–SOFCs. The polarization resistance was 0.067 Ω cm2 at 700 °C for the PrBCM–0.03 cathode on Sm 0.2 Ce 0.8 O 1.9 (SDC) electrolyte. A single cell with PrBCM–0.03 cathode and 300 μm–thick SDC electrolyte showed a maximum power density of 339 mW cm−2 at 700 °C and almost no degradation in performance was detected after a 42 h testing. This study provides a preliminary basis for further research into high–valence ion doping in layered perovskite cathode materials. Image 1 • Mo doped PrBCM- x oxides with x = 0.00–0.07 were evaluated as IT-SOFC cathodes. • TECs of the PrBCM- x exhibit a decrease with increasing Mo. • The R p of PrBCM-0.03 cathode on SDC electrolyte attains 0.067 Ω cm2 at 700 °C. • Cell with PrBCM-0.03 cathode shows good power output and stability. • PrBCM–0.03 is concluded to be the most suitable cathode among PrBCM- x oxides. [ABSTRACT FROM AUTHOR]

Cobalt–free perovskite La 0.5 Sr 0.5 Fe 0.9 Mo 0.1 O 3– δ (LSFMo) was evaluated as the electrode of symmetrical SOFC (S–SOFC) using H 2 and CO as fuels. XRD results demonstrate that the LSFMo electrode is redox stable at a temperature below 800 °C. Furthermore, the chemical compatibility of LSFMo electrode with both Sm 0.2 Ce 0.8 O 1.95 (SDC) and La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3–δ (LSGM) electrolytes was assessed. The thermal expansion coefficients (TECs) of the LSFMo at 30–850 °C are 13.4 × 10−6 K−1 in air and 15.1 × 10−6 K−1 in 5% H 2 /Ar. However, for the pre–reduced LSFMo, the TEC in 5% H 2 /Ar decreases to 11.8 × 10−6 K−1. Using LSFMo as symmetrical electrode of S–SOFCs, the maximum power densities (P max) of 562 mW cm−2 in dry H 2 and 474 mW cm−2 in dry CO at 750 °C are attained based on 300 μm thick SDC electrolyte, while based on the LSGM electrolyte with same thickness, the P max attain 508 mW cm−2 in dry H 2 and 379 mW cm−2 in dry CO. For the LSGM supported S–SOFC, the total polarization resistances (R p) attain 0.460 Ω cm2 in dry H 2 and 1.099 Ω cm2 in dry CO at 750 °C. Additionally, the S–SOFCs with LSFMo electrode exhibit good power cycling stability, long–term stability and multiple redox and thermal cycling stability. Above results indicate that the LSFMo material is a very potential symmetrical electrode for S–SOFCs. • LSFMo was evaluated as electrode of S–SOFCs with SDC/LSGM electrolytes. • LSFMo electrode is redox stable at IT-SOFC operating temperatures. • LSFMo electrode exhibits good thermal expansion match with SDC/LSGM electrolytes. • Good electrochemical performances for S–SOFCs with LSFMo electrode were obtained. • Excellent cell stability for S–SOFCs with LSFMo electrode was obtained. [ABSTRACT FROM AUTHOR]