Fabrication of amorphous TiO2 hydrogen channels and graphene wrappers to enhance the hydrogen storage properties of MgH2 with extremely high cycle stability

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2024-05, Vol.12 (20), p.12190-12197
• Main Authors: Bu, Fanqi, Wajid, Ali, Yang, Na, Gu, Mengyue, Zhao, Xuewen, Huang, Lei, Ji, Xin, Ding, Shujiang, Cheng, Yonghong, Zhang, Jinying
• Format: Article
• Language: English
• Subjects: Amorphous materials; Atomic layer epitaxy; Ball milling; Channels; Conveying; Dehydrogenation; Desorption; Fabrication; Graphene; High temperature; Hydrides; Hydrogen; Hydrogen storage; Hydrogen storage materials; Kinetics; Magnesium; Solid state; Stability; Titanium dioxide
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/d4ta00722k

Magnesium hydrides are promising solid-state hydrogen storage materials due to their high gravimetric hydrogen storage density and low cost. However, the high temperature, slow kinetics, and poor cycle stability hinder the practical application of magnesium hydrides as hydrogen storage materials. Here, amorphous TiO2 was embedded into MgH2 particles as hydrogen conveying channels by atomic layer deposition followed by a ball-milling process to improve their hydrogen adsorption and desorption kinetics. The MgH2 particles embedded with amorphous TiO2 were then wrapped by graphene nanosheets (MgH2–20 nm TiO2@Gra) to enhance their cycle stability. The onset hydrogen desorption temperature of MgH2–20 nm TiO2@Gra has been reduced to 199 °C, which is about 100 °C lower than that of pristine MgH2 (290 °C). MgH2–20 nm TiO2@Gra has been demonstrated to rapidly release 6.04 wt% H2 at 275 °C in 10 min, where only 0.086 wt% H2 was released from pristine MgH2 at 300 °C in 10 min. MgH2–20 nm TiO2@Gra has been found to absorb 5.39 wt% H2 at a temperature as low as 50 °C (30 bar H2), where only 1.67 wt% H2 was absorbed by pristine dehydrogenated MgH2 at 200 °C in 20 min. Moreover, MgH2–20 nm TiO2@Gra has been demonstrated to still release 5.92 wt% of H2 after 50 cycles with a capacity retention of 95.5%. The multivalent Ti+ and abundant oxygen defects have been measured during different de/rehydrogenation states to explore the effects of amorphous TiO2 as hydrogen conveying channels. The amorphous TiO2 hydrogen channels with graphene wrappers have been demonstrated to be an effective strategy to enhance the hydrogen storage properties and cycle stability of MgH2, which is applicable for various solid-state hydrogen storage materials.