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

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.

Automated summary

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