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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]

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]