MgH<sub>2</sub>@Mg(BH<sub>4</sub>)<sub>2</sub> Core-Shell-like Nanostructures: Synthesis, Hydrolysis Performance, and Promotion Mechanism.

Zhu, Yongyang; Zeng, Liming; Wu, Daifeng; Wang, Shun; Zhou, Qing; Tang, Renheng; Chi-Pong Tsui, Gary; Xu, Zheng-Long et al. · Nano Lett · 2024

basic_science · Level V

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Abstract

The hydrolysis of hydrides, represented by MgH<sub>2</sub>, delivers substantial capacity and presents an appealing prospect for an on-site hydrogen supply. However, the sluggish hydrolysis kinetics and low hydrogen yield of MgH<sub>2</sub> caused by the formation of a passivation Mg(OH)<sub>2</sub> layer hinder its practical application. Herein, we present a dual strategy encompassing microstructural design and compounding, leading to the successful synthesis of a core-shell-like nanostructured MgH<sub>2</sub>@Mg(BH<sub>4</sub>)<sub>2</sub> composite, which demonstrates excellent hydrolysis performance. Specifically, the optimal composite with a low <i>E</i><sub>a</sub> of 9.05 kJ mol<sup>-1</sup> releases 2027.7 mL g<sup>-1</sup> H<sub>2</sub> in 60 min, and its hydrolysis rate escalates to 1356.7 mL g<sup>-1</sup> min<sup>-1</sup> H<sub>2</sub> during the first minute at room temperature. The nanocoating Mg(BH<sub>4</sub>)<sub>2</sub> plays a key role in enhancing the hydrolysis kinetics through the release of heat and the formation of local concentration of Mg<sup>2+</sup> field after its hydrolysis. This work offers an innovative concept for the design of hydrolysis materials.