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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]

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]

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 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]

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]