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Protonic ceramic fuel cells (PCFCs) have been the focus of research due to their advantageous properties compared to oxygen ion-conducting solid oxide fuel cells (SOFCs). However, the biggest obstacles to the development of PCFC are the lower proton conductivity and the poor stability in high concentration steam environment. Herein, we report a novel composite cathode with surface reconfiguration, comprised of BaCoO 3-δ (BCO) nanoparticles by water-induced precipitation and Ba 0.9 Pr 0.1 Co 0.7 Fe 0.2 Y 0.1 O 3-δ (BPCFY) substrate with e−/O2−/H+ triple conducting behavior, exhibiting high catalytic activity towards oxygen reduction reaction (ORR) and stability in high steam concentration. With wet hydrogen (3 vol% H 2 O) as fuel and wet air (3 vol% H 2 O) as oxidant, the peak power density of NiO-BZCYYb|BZCYYb|BPCFY single cell reaches 750 mW•cm−2 at 700 °C, approximately 25 % higher than that using dry air at cathode side. Such improvement performance can be attributed to the precipitation of BaCoO 3-δ nanoparticles that increase the active adsorption sites as well as the increased oxygen vacancy concentration by Pr doping in BaCo 0.7 Fe 0.2 Y 0.1 O 3-δ , which synergistically expand the triple phase boundary and facilitate ions migration. This work provided a promising approach to enhance the catalytic activity of PCFC at lower temperatures while also improving its tolerance to steam. • Pr-doping promotes BaCoO 3 nanoparticles precipitation after steam treatment. • Pr-doping improves the ions diffusion process. • The exsolved BaCoO 3 nanoparticles facilitate the gas exchange process. • The composite cathode showed desirable tolerance for steam and carbon dioxide. [ABSTRACT FROM AUTHOR]

Highly efficient and stable cathodes are significantly vital for solid oxide fuel cells (SOFCs). However, one of key impediment to the cathode development is the undesirable oxygen reduction activity and stability with exposure upon steam. Herein, we present a novel nanoparticles-decorated cathode, comprised of O2−/e−/H+ triple-conducting K+-doped BaCo 0.7 Fe 0.2 Y 0.1 O 3-δ (Ba 0.9 K 0.1 Co 0.7 Fe 0.2 Y 0.1 O 3-δ , BKCFY) matrix oxide and the mixed O2−/e− conducting nanoparticles of BaCoO 3-δ (BCO) through water-mediated exsolution process, exhibiting high activity and robust stability with exposure upon the steam. The cathode shows a low polarization resistance of 0.048 Ω cm2 at 700 °C when exposed upon humid air with 3% H 2 O, approximately 24% lower than that in dry air (0.065 Ω cm2 at 700 °C). Such improvement is mainly ascribed to the exsolved BaCoO 3- δ nanoparticles decorated on the porous BKCFY, which enlarged the triple phase boundary for oxygen reduction reaction. The increased oxygen vacancy concentration through K doping can accelerate the Ba and Co ions segregation to form BaCoO 3-δ with exposure upon the wet condition. Furthermore, K+ dopant with higher basicity than Ba2+ is beneficial for hydration behavior, which effectively promotes the catalytic activity under the water vapor. Moreover, the exsolved BaCoO 3-δ nanoparticles are socketed on the BKCFY matrix oxide, which ensures high stability for this hybrid cathode operated at 700 °C. The findings provide a promising approach to design the triple-conducting cathode for solid oxide fuel cells via water-mediated exsolution, which can also be applied for solid oxide electrolysis cells and membrane reactors. [Display omitted] [ABSTRACT FROM AUTHOR]

The significant challenges facing the development of the cathode for intermediate-temperature solid oxide fuel cells (IT-SOFCs) are the poor oxygen reduction reaction (ORR) activity as well as the CO 2 poisoning issues. Herein, an La/Nb co-doped perovskite Ba 0.9 La 0.1 Co 0.7 Fe 0.2 Nb 0.1 O 3- δ (BLCFN) has been developed as a promising cathode for IT-SOFCs. The polarization resistance of BLCFN cathode is 0.073 Ω cm2 at 700 °C air. This remarkable improved ORR activity can be attributed to the increased oxygen vacancies caused by the introduction of La3+ and Nb5+ ions. Furthermore, the collaboration introduction of La3+ and Nb5+ ions greatly reduce the alkalinity of the BLCFN electrode, bringing excellent CO 2 -tolerance for BLCFN cathode. No carbonate is yielded on the surface of the BLCFN cathode. The improvement on CO 2 -tolerance for these cathodes is largely attributed to the introduction of Nb5+ ions, which have higher acidity and more powerful M − O bond, and the introduction of La3+ can improve the ORR activity of the material on this basis. The co-doping of La/Nb elements furtherly stabilizes the lattice structure. Overall, the high ORR activity and CO 2 -tolerance of the cathode manifest a bright application prospect for BLCFN cathode in SOFCs and other membrane reactors. [Display omitted] • A more stable cubic structure is achieved by La/Nb co-doping. • La/Nb co-doping improves the oxygen reduction reaction activity. • BLCFN cathode material exhibits superior resistance towards CO 2 poisoning. • A peak power density of 812 mW cm−2 is achieved at 700 °C with BLCFN cathode. [ABSTRACT FROM AUTHOR]