4.7 Article

Application of nitrogen-doped graphene-supported titanium monoxide as a highly active catalytic precursor to improve the hydrogen storage properties of MgH2

Journal

JOURNAL OF ALLOYS AND COMPOUNDS
Volume 960, Issue -, Pages -

Publisher

ELSEVIER SCIENCE SA
DOI: 10.1016/j.jallcom.2023.170727

Keywords

MgH2; Titanium monoxide; Hydrogen storage material; Catalytic mechanism

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In this study, the addition of highly active catalytic precursor TTONC greatly improved the hydrogen storage properties of MgH2. The TTONC-catalyzed MgH2 could absorb hydrogen at room temperature, and its onset dehydrogenation temperature was significantly lower than that of pristine MgH2. It also exhibited good cyclic stability with a high capacity retention rate after multiple hydrogen absorption-desorption cycles. The catalytic mechanism involved the in situ formation of TiH2, which acted as a hydrogen pump to enhance hydrogen diffusion, and the formation of stable CN layers on the surface of MgH2, which inhibited particle fragmentation and agglomeration. Rating: 8/10
MgH2 has broad prospects in energy storage applications; however, its poor thermodynamic properties and slow hydrogen absorption and desorption rates are unsuitable for commercial needs. In the present work, TiO@N-C (denoted as TTONC), a highly active catalytic precursor, was employed to improve the hydrogen storage properties of MgH2. The TTONC-catalyzed MgH2 could uptake hydrogen at room temperature, and the onset dehydrogenation temperature of TTONC-catalyzed MgH2 was 94 degrees C lower than that of pristine MgH2 (-300 degrees C). Dehydrogenated TTONC-catalyzed MgH2 had a capacity retention rate of 95.2% after 50 hydrogen absorption-desorption cycles. The dehydrogenation and hydrogenation apparent activation energies of MgH2-TTONC were 90.5 kJ.mol-1 and 52.7 kJ.mol-1, respectively. The catalytic mechanism analysis revealed that the in situ formed Ti generated TiH2 in the hydrogenation process, and Ti/TiH2 acted as a hydrogen pump to diffuse hydrogen atoms in the hydrogen absorption/desorption process. The for-mation of stable CN layers with carbon structural defects on the surface of MgH2 inhibited the fragmen-tation and agglomeration of MgH2 particles, and they served as nucleation sites to enhance hydrogen diffusion. Hence, the dehydrogenation/hydrogenation properties and cyclic stability of MgH2 were greatly enhanced by the addition of TTONC.(c) 2023 Elsevier B.V. All rights reserved.

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