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Hollow perovskite oxide La 0·5 Sr 0·5 MnO 3 nanospheres are synthesized by using carbon spheres as template in the presence of citric acid. Among the samples investigated in this work, the one obtained at a sintering temperature of 700 °C exhibits the highest catalytic activity in the oxygen reduction reaction (ORR) in an alkaline electrolyte. The electrochemical measurement data shows that the sample has a positive onset potential (0.860 V) and a high limiting current density (6.48 mA cm−2). Furthermore, the catalyst shows a high selectivity towards methanol and a better stability than a commercial Pt/C catalyst. The hollow La 0·5 Sr 0·5 MnO 3 nanoshperes described in this manuscript hold a great promise for applications in metal-air batteries and alkaline fuel cells. Image 1 • Hollow La 0·5 Sr 0·5 MnO 3 nanospheres were synthesized using template method. • The nanospheres exhibited high ORR activity, good selectivity and durability. • The hollow La 0·5 Sr 0·5 MnO 3 nanospheres are promising noble-metal-free catalyst. [ABSTRACT FROM AUTHOR]

Different transition metals are employed to tune the Y-doped BaZrO 3 proton conductor, resulting in the new BaZr 0.125 Y 0.125 M 0.75 O 3 (M = Cu, Mn, Ni, Zn, Co, and Fe) compositions as cathodes for proton-conducting solid oxide fuel cells. Only Co and Fe dopants can yield pure phases, whereas the use of other dopants results in impurities. Further experimental studies and first-principles calculations show that using Fe dopant has some advantages over Co-doped material, such as increased oxygen vacancies, lower proton migration energy barriers, and faster proton and oxygen diffusion kinetics. The fuel cell employing the BaZr 0.125 Y 0.125 Fe 0.75 O 3 (BZYFe) cathode has a larger fuel cell output than the fuel cell using the BaZr 0.125 Y 0.125 Co 0.75 O 3 (BZYCo) cathode. Furthermore, the CO 2 adsorption energy on the BZYFe surface is larger than that at the BZYCo surface, indicating that BZYFe has significantly better chemical stability than BZYCo. The long-term stability of the fuel cell demonstrates that the fuel cell with the BZYCo cathode is degrading. In contrast, the BZYFe cell has good operating stability. Given its phase purity, fuel cell performance, and stability, the Fe element is an appropriate dopant for altering BZY and creating a new cathode. • BaZr 0.125 Y 0.125 M 0.75 O 3 (M = Cu, Mn, Ni, Zn, Co, and Fe) were prepared. • Only Co and Fe dopants can generate pure phases. • BaZr 0.125 Y 0.125 Co 0.75 O 3 and BaZr 0.125 Y 0.125 Fe 0.75 O 3 cathodes yielded similar cell performance. • The cell using BaZr 0.125 Y 0.125 Fe 0.75 O 3 cathode showed better operational stability. [ABSTRACT FROM AUTHOR]

Abstract: La0.3Sr0.7FeO3-δ (LSF)/CeO2 cathode supported Ce0.8Sm0.2O2-δ (SDC) electrolyte was prepared by a simple multilayer tape casting and co-firing method. SDC electrolyte slurry and LSF/CeO2 cathode slurry were optimized and the green bi-layer tapes were co-fired at different temperature. Phase characterizations and microstructures of electrolyte and cathode were studied by X-ray diffraction (XRD) and Scan Electronic Microscopy (SEM). No additional phase peak line was observed in electrolyte and cathode support when the sintering temperature lower was than 1400°C. The electrolytes were extremely dense with the thickness of about 20μm. The cathode support was porous with electrical conductivity of about 4.21S/cm at 750°C. With Ni/SDC as anode, Open Current Voltage and maximum power density reached 0.61V and 233mWcm−2 at 750°C, respectively. [Copyright &y& Elsevier]

Abstract: A high In-dopant level BaCeO3 material was used as an electrolyte for a proton-conducting solid oxide fuel cell (SOFC). Indium behaved as an ideal dopant for BaCeO3, which improved both the chemical stability and sinterability for BaCeO3 greatly. The anode supported BaCe0.7In0.3O3−δ (BCI30) membrane reached dense after sintering at 1100°C, much lower than the sintering temperature for other BaCeO3-based materials. Additionally, the BCI30 membrane showed adequate chemical stability against CO2 compared with the traditional rare earth doped BaCeO3. The BCI30-based fuel cell also showed a reasonable cell performance and a good long-term stability under the operating condition. Besides, the LaSr3Co1.5Fe1.5O10−δ (LSCF) was also evaluated as a potential cathode candidate for a proton-conducting SOFC. [Copyright &y& Elsevier]

A Sr-deficiency approach is utilized to adjust the composition of the standard Sr 2-x Fe 1.5 Mo 0.25 Sc 0.25 O 6 (SFMS) material, with the goal of improving the performance of the SFMS cathode in proton-conducting solid oxide fuel cells (H–SOFCs). The Sr-deficiency concentration is restricted to 10% at the Sr site, and an increase in Sr-deficiency leads to the formation of more oxygen vacancies. However, the presence of increased oxygen vacancies does not consistently enhance the diffusion capabilities of charge carriers. The excess of oxygen vacancies impedes the movement of oxygen and protons. The optimal oxygen and proton transport capabilities are achieved when the Sr-deficiency level is set at 5%. Specifically, this is observed in the compound Sr 1.9 Fe 1.5 Mo 0.25 Sc 0.25 O 6 (S1.9FMS). The enhanced oxygen and proton diffusion kinetics enable H–SOFCs to achieve exceptional performance when employing the S1.9FMS cathode, reaching a power density of 1709 mW cm−2 at 700 °C with a low polarization resistance of 0.023 Ω cm2. The fuel cell's output exceeds that of many previously reported H–SOFCs. Furthermore, the fuel cell utilizing the S1.9FMS cathode not only exhibits excellent fuel cell performance but also maintains reliable operational stability. This indicates that employing the Sr-deficiency technique with an appropriate level of deficiency is a successful approach to enhance the cathode performance for H–SOFCs. • A Sr-deficiency approach was used to tailor Sr 2-x Fe 1.5 Mo 0.25 Sc 0.25 O 6 (SFMS). • The Sr-deficient SFMS showed improved oxygen and proton diffusion kinetics. • A high fuel cell performance was obtained with the Sr 1.9 Fe 1.5 Mo 0.25 Sc 0.25 O 6 cathode. • Good stability was retained for the Sr 1.9 Fe 1.5 Mo 0.25 Sc 0.25 O 6 cathode. [ABSTRACT FROM AUTHOR]

Transition metal elements were employed to customize the standard Sr 2 Fe 1.5 Mo 0.5 O 6 (SFM) material, with the goal of improving the performance of the SFM cathode in proton-conducting solid oxide fuel cells (H–SOFCs). Sr 2 FeMo 0.5 X 0.5 O 6 (X = Ni, Co, Mn, Zn) materials were prepared, but it was discovered that only the dopants Ni and Co can form a pure phase, whereas the dopants Mn and Zn produced an obvious secondary phase. When comparing oxygen vacancies and oxygen diffusion kinetics, utilizing the Co-dopant exhibited clear advantages. The Co-doped SFM had a higher oxygen vacancy content and faster oxygen diffusion kinetics than both the standard and Ni-doped SFM cathodes. The energy barrier for the oxygen reduction reaction (ORR) at the Co-doped SFM cathode was 0.76 eV, which was much lower than that for the SFM and Ni-doped SFM, which were 5.52 and 2.28 eV, respectively. As a result, the Co-doped SFM's cathode reaction was greatly accelerated, resulting in a high fuel cell performance of 1306 mW cm−2 at 700 °C. This finding suggests that using the appropriate dopant can alleviate the low-performance problem of the traditional SFM cathode, resulting in a promising cathode option for H–SOFCs. • Sr 2 FeMo 0.5 X 0.5 O 6 (X = Ni, Co, Mn, Zn) cathodes were proposed for H–SOFCs. • The Co dopant showed more advantages compared with other dopants. • The Sr 2 FeMo 0.5 Co 0.5 O 6 cathode delivered high fuel cell performance. • The mechanism for the enhanced cathode performance was revealed. [ABSTRACT FROM AUTHOR]

LaNi 0.5 Fe 0.5 O 3-δ (LNF) is a viable option for the cathode of solid oxide fuel cells (SOFCs), however, its performance in proton-conducting SOFCs (H–SOFCs) is not sufficient. In this work, an Sc-doped method to increase the cathode performance of conventional LNF for H–SOFCs is proposed. Although the Sc cation can be doped at the Ni site or the Fe site in LNF, which led to the formation of pure phase materials, first-principles calculations indicate that the formation of the LaNi 0.4 Sc 0.1 Fe 0.5 O 3-δ (LNSF) material has more advantages than the formation of the LaNi 0.5 Fe 0.4 Sc 0.1 O 3-δ (LNFS) material, even though the same Sc-doping level is employed. Compared to Sc-free LNF, LNSF provides superior fuel cell performance. At 700 °C, the LNSF cell generates a peak power density of 1534 mW cm−2, double that of the LNF cell. In addition, employing the LNSF cathode reduces the cell's polarization resistance, indicating that the Sc-doping strategy paired with selecting the doping site is an effective method for reusing LNF in high-performance H–SOFCs. • Sc cations can be doped at the Fe or Ni sites in LaNi 0.5 Fe 0.5 O 3-δ (LNF). • The site occupation at the Ni site shows advantages compared with that at the Fe site. • Sc-doped LNF shows better performance than the Sc-free one. • The performance of the cell using LaNi 0.4 Sc 0.1 Fe 0.5 O 3-δ is better. [ABSTRACT FROM AUTHOR]

As a cathode material for proton-conducting SOFCs (H–SOFCs), a novel MnCo 1.9 Sb 0.1 O 4 (MCSO) spinel material was suggested. The MCSO material was effectively produced, and it demonstrated excellent phase stability at elevated temperatures and chemical stability against CO 2 and H 2 O. Doping Sb into the MnCo 2 O 4 (MCO) allowed for enhanced proton diffusion and surface exchange, as evidenced by electrical conductivity relaxation tests. In addition, an oxygen-vacancy-rich surface was developed for the MCSO material, resulting in the possibility of a high cathode oxygen reduction reaction activity. The MCSO material was examined in the H–SOFC application, and the fuel cell with an MCSO cathode attained a high power density of 1380 mW cm−2 at 700 °C. At 700 °C, the cell employing the Sb-free MCO cathode, which had a comparable cell microstructure to the MCSO cell, only obtained a peak power density of 836 mW cm−2. The higher cell performance resulted from the Sb-modified MCO cathode's increased catalytic activity. In addition, the MCSO cell displayed excellent operational stability under fuel cell operating conditions, indicating that MCSO is a novel and effective spinel cathode for H–SOFCs. • A new MnCo 1.9 Sb 0.1 O 4 (MCSO) spinel was proposed for H–SOFCs. • Doping Sb into MnCo 2 O 4 (MCO) enhanced proton diffusion and surface exchange. • MCSO improved the cathode activity compared with Sb-free MCO. • A high performance was obtained for the fuel cell using MCSO cathode. [ABSTRACT FROM AUTHOR]

A new honeycomb-shaped La 0·5 Sr 0·5 Fe 0·9 P 0·1 O 3-δ (LSFP) material has been proposed as a cathode for proton-conducting solid oxide fuel cells (H–SOFCs). Compared with conventional LSFP, the honeycomb-shaped does not change the crystal structure or the electronic structure of the material but offers a much higher surface area. The unique honeycomb structure allows the easier diffusion of air and H 2 O evaporations in the cathode, thus benefiting the application of LSFP as a cathode for LSFP. The honeycomb LSFP cathode's fuel cell shows a peak power density of 1474 mW cm−2 at 700 °C, which is higher than the conventional LSFP cell. In addition, the fuel cell performance is also the highest ever reported for H–SOFCs based on the Sr-doped LaFeO 3 (LSF) cathodes, making a new life for the first-generation LSF cathode for H–SOFCs. The distribution of relaxation times (DRT) analysis for the cell reveals that the honeycomb-shaped cathode improves the oxygen reduction reaction (ORR) at the cathode, thus improving the cathode kinetics. • A honeycomb-shaped La 0·5 Sr 0·5 Fe 0·9 P 0·1 O 3-δ (LSFP) material has been prepared. • The honeycomb structure improved the surface area. • The cell using the honeycomb LSFP cathode showed higher fuel cell performance. • The performance enhancement mechanism was studied. [ABSTRACT FROM AUTHOR]

A series of W doped Pr 0.5 Ba 0.5 (Co 0.7 Fe 0.3)O 3-δ (PBCF) are prepared and characterized as cathodes for proton-conducting solid oxide fuel cell (H–SOFC). The enhancement of proton migration and formation ability through W doping significantly increases the cell performance and it is further verified by the density functional theory (DFT) simulation, presenting the high valence element doping can be a potential approach for the design of cathode. • W doped PBCF at proper concentration can form Single and double perovskite composites. • The performance of H-SOECs is highly improved by applying this novel element. • Proton migration and transportation energies are calculated using DFT method. [ABSTRACT FROM AUTHOR]

A Zn-doping strategy is employed to tailor the LaNi 0.5 Fe 0.5 O 3-δ material to improve its performance for proton-conducting solid oxide fuel cells (H–SOFCs). Zn can partially replace Ni in the LaNi 0.5 Fe 0.5 O 3-δ lattice to form LaNi 0.4 Zn 0.1 Fe 0.5 O 3-δ material. In contrast, ZnO secondary phase can be detected if attempts are made to partially replace Fe with Zn, and the nominal composition LaNi 0.5 Fe 0.4 Zn 0.1 O 3-δ cannot be obtained. First-principles calculations indicate that the Zn-doping method lowers the formation energy of oxygen vacancy and decreases the hydration energy, benefiting its application as the cathode for H–SOFCs. As a result, the H–SOFC with the LaNi 0.4 Zn 0.1 Fe 0.5 O 3-δ cathode generates a peak power density of 1226 mW cm−2 at 700 °C. In contrast, the peak power density for the cell using the Zn free LaNi 0.5 Fe 0.5 O 3-δ cathode only reaches 722 mW cm−2 at the same testing temperature. The polarization resistance of the cell with the LaNi 0.4 Zn 0.1 Fe 0.5 O 3-δ cathode is reduced to 0.043 Ω cm2 at 700 °C, which is one of the smallest reported for H–SOFCs using cobalt-free cathodes. The high fuel cell performance coupled with the low polarization resistance for the Zn-modified LaNi 0.5 Fe 0.5 O 3-δ suggests that the Zn-doping strategy would be an interesting way to promote the performance of the cobalt-free LaNi 0.5 Fe 0.5 O 3-δ material for H–SOFCs. • A new LaNi 0.4 Zn 0.1 Fe 0.5 O 3-δ material has been prepared. • Zn-doping improved the material's properties for H–SOFCs. • High cell performance of 1226 mW cm−2 at 700 °C was obtained with the new cathode. • First-principles calculations were used to reveal the mechanism. [ABSTRACT FROM AUTHOR]

The application of traditional MIEC cathode material Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ (BSCF) in the solid oxide fuel cell (SOFC) field is limited due to its susceptibility to CO 2 and high thermal expansion coefficient. Therefore, improving the stability of BSCF cathode in CO 2 -containing environments and the matching degree between BSCF and electrolyte are the key factors to achieve its excellent electrochemical and stable performance for intermediate temperature solid oxide fuel cells (IT-SOFCs). Herein, the cathode materials Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2-x Ta x O 3-δ (X = 0, 0.1, 0.2) are successfully prepared and the effects of Ta-doped content are investigated systematically. With the increase of Ta-doped content, the thermal expansion coefficient of BSCF 0.2-x T x decreases from 25.1 × 10−6 K−1 to 16.5 × 10−6 K−1, which indicated that Ta-doped enhanced the combination of cathode material and electrolyte. In single-cell applications, the maximum power density of 926.4 mW cm−2 and the lowest polarization resistance of 0.06 Ω cm2 at 700 °C are achieved. Furthermore, theoretical calculations show that the CO 2 adsorption energy of BSCFT is 0.12 eV higher than that of BSCF, indicating that BSCFT exhibited improved resistance to CO 2 corrosion compared with BSCF. It is indicated that the Ta-doping strategy has the advantage of improving both the performance and stability of BSCF cathode materials. • BSCF cathode materials doped with different concentrations of Ta were prepared. • The good stability of Ta-doped BSCF cathode materials were confirmed. • The effect of Ta doping on CO 2 resistance was analyzed by theoretical calculations. • BSCF 0.1 T 0.1 material achieved excellent fuel cell performance with good stability. [ABSTRACT FROM AUTHOR]

The synthesis of ammonia (NH 3) from electrochemical nitrogen reduction reaction (NRR) under environmental conditions is a promising technology. Compared with the traditional artificial nitrogen fixation process by the Haber-Bosch process, electrochemical nitrogen reduction reaction (NRR) requires no harsh reaction conditions. In this work, we report that Bi-doped CeO 2 nanocubes show high NRR activity as electrocatalysts. The NH 3 yield of 17.83 μgh−1 mg−1 cat. and the Faradaic Efficiency (FE) of 1.61% at −0.9 V are achieved in 0.1 M Na 2 SO 4. The performance is much higher than that for the traditional CeO 2 nanoparticles. The detailed analysis indicates that both the Bi doping and the cube morphology are critical for this encouraging NRR performance. The mechanism for improving NRR is further explored with first-principle calculations, demonstrating the importance of Bi-doping for performance enhancement. • Nano Bi 0.2 Ce 0.8 O 2-δ with cube shape shows high NRR performance. • Bi-doping is critical for the high performance. • Insights for reaction mechanism were revealed with first principle calculations. [ABSTRACT FROM AUTHOR]

Abstract: The cermet consisting of electronic conductor Ni and proton conductor La2Ce2O7 (LDC) shows good chemical stability but poor hydrogen permeability. In order to improve the hydrogen permeability, novel Ni–La2−x Sm x Ce2O7 (x =0, 0.025, 0.05, 0.075, 0.1 and 0.2) cermets were developed for hydrogen separation. The results show that Sm element doping of LDC can affect the rate of hydrogen permeation, with Ni–La1.95Sm0.05Ce2O7 possessing the highest hydrogen permeation fluxes. [Copyright &y& Elsevier]

The electrochemical conversion of N 2 to NH 3 is an interesting research topic as it provided an alternative and energy-saving method compared with the traditional way of NH 3 production. Although different materials have been proposed for N 2 reduction, the use of defects in oxides was only reported recently and the relevant working mechanism was not fully revealed. In this study, Sr was used as the dopant for LaFeO 3 to create oxygen vacancies, forming the Sr-doped LFO (La 0.5 Sr 0.5 FeO 3-δ) perovskite oxide. The La 0.5 Sr 0.5 FeO 3-δ ceramic oxide used as a catalyst achieves an NH 3 yield of 11.51 μgh−1 mg−1 and the desirable faradic efficiency (F.E.) of 0.54% at −0.6 V vs reversible hydrogen electrode (RHE), which surpassed that of LaFeO 3 nanoparticles. The 15N isotope labeling method was employed to prove the La 0.5 Sr 0.5 FeO 3-δ catalyst had the function of converting N 2 into NH 3 under the electrolysis condition. The first principle calculations were used to investigate the mechanism at the atomistic level, revealing that the free energy barriers changed significantly with the introduction of oxygen vacancies that accelerated the overall nitrogen reduction reaction (NRR) procedure. Image 1 • Perovskite oxides were used for nitrogen reduction reaction. • The oxide with oxygen vacancy showed better nitrogen reduction reaction performance. • Isotope labeling experiment confirmed the conversion of nitrogen to ammonia. • The role of oxygen vacancy in reactions was revealed by first-principle calculations. [ABSTRACT FROM AUTHOR]

PrBaCo 2 O 5+δ (PBC) with high catalytic activity is identified as a prospective cathode material for intermediate temperature solid oxide fuel cells (IT-SOFCs). However, its poor chemical stability hinders its application. To address this problem, a Ta-doping strategy was presented in this study. The cathode with Ta-doping PBC was applied in proton conducting SOFCs. And the influence of Ta-doping on the crystal structure, electrochemical performance, structure stability and electrical conductivity of PBC was investigated. The resistance to CO 2 of PBC at elevated temperature is significantly improved with Ta-doping. The electrochemical performance measurements indicated that a low Ta-doping concentration did not change the performance of the cells obviously, while large Ta-doping concentration could lower the fuel cell performance. • Tantalum element was successfully doped into the crystal lattice of PBC. • Ta-doped PBC was successfully applied in H–SOFC. • The resistance to CO 2 of PBC at elevated temperature is significantly improved with Ta-doping. [ABSTRACT FROM AUTHOR]