Stabilizing γ-MgH<sub>2</sub> at Nanotwins in Mechanically Constrained Nanoparticles.
basic_science · Level V
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- Record sourced from PubMed, PMID 33554349.
- Also identified by DOI 10.1002/adma.202008259 and PMC identifier 11468506.
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Abstract
Reversible hydrogen uptake and the metal/dielectric transition make the Mg/MgH<sub>2</sub> system a prime candidate for solid-state hydrogen storage and dynamic plasmonics. However, high dehydrogenation temperatures and slow dehydrogenation hamper broad applicability. One promising strategy to improve dehydrogenation is the formation of metastable γ-MgH<sub>2</sub> . A nanoparticle (NP) design, where γ-MgH<sub>2</sub> forms intrinsically during hydrogenation is presented and a formation mechanism based on transmission electron microscopy results is proposed. Volume expansion during hydrogenation causes compressive stress within the confined, anisotropic NPs, leading to plastic deformation of β-MgH<sub>2</sub> via (301)<sub>β</sub> twinning. It is proposed that these twins nucleate γ-MgH<sub>2</sub> nanolamellas, which are stabilized by residual compressive stress. Understanding this mechanism is a crucial step toward cycle-stable, Mg-based dynamic plasmonic and hydrogen-storage materials with improved dehydrogenation. It is envisioned that a more general design of confined NPs utilizes the inherent volume expansion to reform γ-MgH<sub>2</sub> during each rehydrogenation.