Effects of Graphene/Silver Nanocomposite on the Microstructure of Amorphous Mg–based Hydride

• Published in: International journal of electrochemical science 2016-12, Vol.11 (12), p.10379-10390
• Main Authors: Lin-jun, Huang, Yan-xin, Wang, Jian-guo, Tang, Yao, Wang, Ji-xian, Liu, Ji-qing, Jiao, Wei, Wang
• Format: Article
• Language: English
• Subjects: electrochemical property; electrode alloy; graphene coating; surface modification
• ISSN: 1452-3981; 1452-3981
• DOI: 10.20964/2016.12.10

The influence of a graphene/silver (G/A) nanocomposite coating layer on the microstructural evolution and surface oxidation of a Mg–Ni–La hydride is investigated systematically by XRD, SEM, EDS and HRTEM in detail. SEM and EDS reveal that the existence of the G/A composite prevents the electrode from pulverizing and oxidizing. The oxygen content in the surface of the electrode is reduced from 21.26% to 9.83% after 50 cycles for a Mg-Ni-La electrode with 0.2 mass fraction of G/A. HRTEM shows that the amorphous electrodes with no G/A coating are almost all crystallized, and that the stable Mg2NiH4, α-Mg, MgH2 and LaH2 phases are present with grain sizes as large as 100-120 nm after 50 cycles of charging/discharging. The G/A coating reduces the corrosion and oxidation of the electrode alloy and provides both a pathway for hydrogen diffusion and active sites for the redox reaction of hydrogen. All these factors generate a significant enhancement of the discharge capacity by about 250 mAhg-1 in each cycle (after activation) for Mg-Ni-La electrodes with 0.2 G/A nanocomposites.