Oxygen Vacancy-Rich 2D TiO2 Nanosheets: A Bridge Toward High Stability and Rapid Hydrogen Storage Kinetics of Nano-Confined MgH2

Li Ren; Wen Zhu; Yinghui Li; Xi Lin; Hao Xu; Fengzhan Sun; Chong Lu; Jianxin Zou

doi:10.1007/s40820-022-00891-9

Oxygen Vacancy-Rich 2D TiO₂ Nanosheets: A Bridge Toward High Stability and Rapid Hydrogen Storage Kinetics of Nano-Confined MgH₂

Nanomicro Lett. 2022 Jul 15;14(1):144. doi: 10.1007/s40820-022-00891-9.

Authors

Li Ren^{1

2

3}, Wen Zhu¹, Yinghui Li¹, Xi Lin¹, Hao Xu¹, Fengzhan Sun¹, Chong Lu⁴, Jianxin Zou^{5

6

7}

Affiliations

¹ National Engineering Research Center of Light Alloys Net Forming & State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai, 200240, People's Republic of China.
² Shanghai Engineering Research Center of Mg Materials and Applications & School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, People's Republic of China.
³ Center of Hydrogen Science, Shanghai Jiao Tong University, Shanghai, 200240, People's Republic of China.
⁴ Instrumental Analysis Center of SJTU, Shanghai Jiao Tong University, Shanghai, 200240, People's Republic of China.
⁵ National Engineering Research Center of Light Alloys Net Forming & State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai, 200240, People's Republic of China. zoujx@sjtu.edu.cn.
⁶ Shanghai Engineering Research Center of Mg Materials and Applications & School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, People's Republic of China. zoujx@sjtu.edu.cn.
⁷ Center of Hydrogen Science, Shanghai Jiao Tong University, Shanghai, 200240, People's Republic of China. zoujx@sjtu.edu.cn.

Abstract

MgH₂ has attracted intensive interests as one of the most promising hydrogen storage materials. Nevertheless, the high desorption temperature, sluggish kinetics, and rapid capacity decay hamper its commercial application. Herein, 2D TiO₂ nanosheets with abundant oxygen vacancies are used to fabricate a flower-like MgH₂/TiO₂ heterostructure with enhanced hydrogen storage performances. Particularly, the onset hydrogen desorption temperature of the MgH₂/TiO₂ heterostructure is lowered down to 180 °C (295 °C for blank MgH₂). The initial desorption rate of MgH₂/TiO₂ reaches 2.116 wt% min^-1 at 300 °C, 35 times of the blank MgH₂ under the same conditions. Moreover, the capacity retention is as high as 98.5% after 100 cycles at 300 °C, remarkably higher than those of the previously reported MgH₂-TiO₂ composites. Both in situ HRTEM observations and ex situ XPS analyses confirm that the synergistic effects from multi-valance of Ti species, accelerated electron transportation caused by oxygen vacancies, formation of catalytic Mg-Ti oxides, and stabilized MgH₂ NPs confined by TiO₂ nanosheets contribute to the high stability and kinetically accelerated hydrogen storage performances of the composite. The strategy of using 2D substrates with abundant defects to support nano-sized energy storage materials to build heterostructure is therefore promising for the design of high-performance energy materials.

Keywords: Hydrogen storage; MgH2; Nanoconfinement; Oxygen vacancies; TiO2 nanosheets.