Vanadium diselenide (VSe2), a member of the transition metal dichalcogenides (TMDs) family, is emerging as a promising two-dimensional (2D) candidate for the electronic and spintronic device with exotic properties including charge/spin density wave and ferromagnetism. The bulk crystal VSe2 exists in a crystallographic form of 1T-phase with metallic behavior. In this paper, we report a structural phase transition of multilayer VSe2 from 1T to 2H through annealing at 650 K, accompanying a metal–insulator transition. We observe that the 2H-phase is more thermodynamically favorable than the 1T-phase at 2D.

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Magnesium hydride (MgH 2) offers excellent capacity to store hydrogen, but it suffers from the high desorption temperature (>283 C for starting release hydrogen). In this work, we calculated the hydrogen desorption energy of Mg 76 H 152 clusters with/without non-metal dopants by density functional theory method. Phosphorus (P), as identified as the best dopant, can reduce the reaction energy for releasing one hydrogen molecule from 0.75 eV (bulk MgH 2) to 0.20 eV. Inspired by the calculation, P-doped ordered mesoporous carbon (CMK-3) was synthesized by one-step method and employed as the scaffold for loading MgH 2 nanoparticles, forming MgH 2 @P/CMK-3. Element analysis shows that phosphorus dopants have been incorporated into the CMK-3 scaffold and magnesium and phosphorus elements are well-distributed in carbon scaffold hosts. Tests of hydrogen desorption confirmed that P-doping can remarkably enhance the hydrogen release properties of nanoconfined MgH 2 at low temperature, specifically $1.5 wt. % H 2 released from MgH 2 @P/CMK-3 below 200 C. This work, based on the combination of computational calculations and experimental studies, demonstrated that the combined approach of non-metal doping and nano-confinement is promising for enhancing the hydrogen desorption properties of MgH 2 , which provides a strategy to address the challenge of hydrogen desorption from MgH 2 at mild operational conditions.

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