Effect of octahedral occupancy of bimetal-doping and CO2-induced surface reconstruction on oxygen reduction reaction of cobalt-based perovskite oxides

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2024-04, Vol.485, p.149770, Article 149770
• Main Authors: Wang, Haocong, Zhu, Wanfeng, Gong, Jian, Guan, Min, Xu, Lanlan, Zhang, Wenwen, Liu, Xiaojuan, Yan, Chenglin, Meng, Jian
• Format: Article
• Language: English
• Subjects: Bimetal-doping; Oxygen reduction reaction; Solid oxide fuel cell; Surface activation
• ISSN: 1385-8947
• DOI: 10.1016/j.cej.2024.149770

Zr and Sc co-doping transforms hexagonal BCF into cubic BCFZS, and their occupancy in octahedron affects surface oxygen exchange process. Meanwhile, CO2 induces positive surface reconstruction, which significantly enhance ORR catalytic activity of BCFZS. [Display omitted] •The effect of Zr/Sc octahedral occupancy on ORR kinetics is investigated.•BCFZS cathode shows high ORR catalytic activity and excellent durability.•ORR activity is significantly enhanced by CO2-induced surface reconstruction.•The in-situ diffusion of elements at TPB promotes the conduction of O2–. The development of efficient and durable cathode materials plays an important role in the wide application of intermediate-temperature solid oxide fuel cell (IT-SOFC). Herein, Zr and Sc co-doped BaCo0.7Fe0.3O3−δ perovskite oxides are investigated as oxygen reduction reaction (ORR) catalysts. Zr/Sc co-doping successfully realizes the transformation from hexagonal structure to cubic structure. It proves that the occupancy of Zr and Sc in octahedron affects surface oxygen exchange process, especially the dissociation and reduction of oxygen. Among them, Ba(Co0.7Fe0.3)0.8Zr0.1Sc0.1O3−δ (BCFZS) cathode shows high ORR catalytic activity and excellent durability in the intermediate-temperature region. For example, its polarization resistances are 0.0513 and 0.418 Ω cm2 at 700 and 550 ℃, respectively. An anode-supported single cell with BCFZS cathode displays high peak power density (1.0 W cm−2 at 700 ℃) and excellent durability (∼100 h at 600 ℃), the total degradation rate is only ∼ 0.0064 % h−1. Notably, CO2-treatment further enhances ORR kinetics. This is mainly because the degree of chemical adsorption of CO2 at Ba-site is tailored by Zr/Sc co-doping, achieving positive surface reconstruction (nano-BaCO3 decoration) rather than severe CO2-poisoning. Meanwhile, in-situ interdiffusion of La, Co, and Mg promotes interfacial combination and oxygen ions conduction.