Regulating the d-p orbital hybridization in BaCo0.4Fe0.4Zr0.1Y0.1O3-δ via Cu doping for high-performance solid oxide fuel cells cathode

The BaCo_0.4Fe_0.4Zr_0.1Y_0.1O_3-δ (BCFZY) perovskite oxide is a highly promising cathode material for solid oxide fuel cells (SOFCs), mainly due to its exceptional three-phase conductivity at the elevated temperatures and remarkable oxygen reduction reaction (ORR) activity. Nevertheless, its limited electronic and ionic conductivities at relatively lower temperatures poses a significant challenge for its low-temperature applications. To address this issue, the Cu doping in the B-site of BCFZY is proposed. It is observed that Cu doping significantly enhances both the electronic conductivity and oxygen exchange kinetics, leading to a notable reduction in polarization resistance and a substantial improvement in ORR catalytic activity. Specifically, the Ni-YSZ anode-supported single cell equipped with BCFZYCu4 as the cathode exhibits a remarkable power density of 1.30 W cm⁻² at 700 ℃, which surpasses that of the single cell with BCFZY cathode by 51.16 %. An in-depth mechanism study has revealed that the enhanced performance is closely linked to the increased orbitals hybridization induced by Cu doping. This not only enlarges the covalency of the Co-O/Cu–O bonds but also shifts the metal 3d and O 2p band center closer to the Fermi level, which significantly facilitates the oxygen adsorption, dissociation, and oxygen ion exchange processes of the BCFZYCu4 cathode.