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

MgH 2 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 MgH 2 . The TTONC-catalyzed MgH 2 could uptake hydrogen at room temperature, and the onset dehydrogenation temperature of TTONC-catalyzed MgH 2 was 94 °C lower than that of pristine MgH 2 (∼300 °C). Dehydrogenated TTONC-catalyzed MgH 2 had a capacity retention rate of 95.2% after 50 hydrogen absorption-desorption cycles. The dehydrogenation and hydrogenation apparent activation energies of MgH 2 -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 TiH 2 in the hydrogenation process, and Ti/TiH 2 acted as a hydrogen pump to diffuse hydrogen atoms in the hydrogen absorption/desorption process. The formation of stable CN layers with carbon structural defects on the surface of MgH 2 inhibited the fragmentation and agglomeration of MgH 2 particles, and they served as nucleation sites to enhance hydrogen diffusion. Hence, the dehydrogenation/hydrogenation properties and cyclic stability of MgH 2 were greatly enhanced by the addition of TTONC.