Effect of Equivalent La and Ce Substitution for Y on the Structure and Properties of A2B7‑Type La–Y–Ni-Based Hydrogen Storage Alloys

• Published in: Journal of physical chemistry. C 2024-11, Vol.128 (44), p.18950-18961
• Main Authors: Xu, Guandong, He, Xiangyang, Ma, Yucheng, Zhou, Shujuan, Zhang, Xu, Zhao, Yuyuan, Xiong, Wei, Li, Baoquan, Wang, Li, Yan, Huizhong
• Format: Article
• Language: English
• Subjects: C: Physical Properties of Materials and Interfaces
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.4c04818

A2B7-type (LaCe) x Y6–2x Ni18.5Mn1.5Al (x = 0.95, 1.00, 1.15, 1.20, 1.25, 1.30) alloys were prepared by a vacuum induction-quenching process and annealed at 1148 K for 16 h. The structure and properties of the alloys were tested by X-ray diffraction (XRD), scanning electron microscopy (SEM), pressure–composition–temperature curve (PCT), and electrochemical methods. It is found that the alloys are mainly composed of the Ce2Ni7 (2H) and Gd2Co7 (3R) phase, and a decrease of the Y content is beneficial to the formation of the Ce2Ni7 phase. With the partial substitution of Y by equivalent La and Ce, the alloy electrodes with a moderate Y/(LaCe) ratio have relatively large discharge capacity, while the capacity retention rate increases gradually from 63.2% (x = 0.95) to 69.2% (x = 1.30) after 100 cycles. The alloy with the highest Y content shows the best electrochemical kinetic performance due to good hydrogen diffusion ability and surface reactivity. This work provides new ideas and theoretical guidance for the composition optimization of La–Y–Ni-based hydrogen storage alloys.