Enhancing Activity and Durability of A-Site-Deficient (La_0.6Sr_0.4)_0.95Co_0.2Fe_0.8O_3−δ Cathode by Surface Modification with PrO_2−δ Nanoparticles

Abstract

The development of efficient and durable electrocatalysts for oxygen reduction reaction (ORR) is essential for the application of intermediate-temperature solid oxide fuel cells (IT-SOFCs). Here, we report our findings in notably improving ORR dynamics and stability of A-site-deficient (La0.6Sr0.4)0.95Co0.2Fe0.8O3−δ (LSCF) cathode using PrO2−δ/Pr0.8Ce0.2O2−δ nanoparticles. The LSCF + PrO2−δ cathode shows an area-specific resistance of ∼0.241 Ω cm2 at 600 °C, which is about 67% lower than that of pristine LSCF cathode (∼0.738 Ω cm2). Furthermore, anode-supported single cells with LSCF + PrO2−δ/Pr0.8Ce0.2O2−δ cathodes show excellent peak power densities (∼1457.8 mW cm–2 at 700 °C and ∼516.7 mW cm–2 at 550 °C) and enhanced durability (0.9 A cm–2 for ∼100 h). X-ray photoelectron spectroscopy and transmission electron microscopy analyses indicate that PrO2−δ accelerates ORR kinetics by creating an active surface with abundant oxygen vacancies and improving ionic conductivity. The active surface promotes cation migration, leading to the formation of active SrxCoyOz, which may further contribute to the improvement of ORR kinetics. It is found that the distinctive LSCF/SrxCoyOz/PrO2−δ heterostructure plays a vital role in improving the surface stability of LSCF cathode, and the strategy of adjusting the intrinsic activity and thermal expansion behavior of catalytic coatings has also proven to be effective in enhancing the durability of an electrode.