Improved hydrogen storage properties of MgH2 by the addition of TiCN and its catalytic mechanism

The hydrogen storage properties of MgH 2 – x wt%TiCN ( x  = 5, 10, 15) composites were systematically investigated and the results show that the addition of TiCN can effectively improve the de/rehydrogenation kinetics of MgH 2 . Taken the onset dehydrogenation temperature and isothermal de/rehydrogenation kinetics into consideration, the MgH 2 –10 wt% TiCN composite was shown to have the best performance. It was found that the MgH 2 –10 wt% TiCN composite could release 4 wt% H 2 in 17.3 min at 300 °C while the as-synthesized MgH 2 could not release any hydrogen under the same condition. Besides, the MgH 2 –10 wt% TiCN composite could absorb 4.63 wt% H 2 under 3.2 MPa hydrogen pressure at 300 °C within 20 s. Compared with as-synthesized MgH 2 , the activation energy of the MgH 2 –10 wt% TiCN composite was significantly decreased from 183.76 ± 10 to 106.82 ± 5 kJ/mol. X-ray diffraction analysis revealed that the TiCN remained stable during the ball milling and the following de/rehydrogenation cycle. The catalytic mechanism was also proposed that the TiCN particles absorbed on MgH 2 not only served as charge transfer centers and accelerated the hydrogen incorporation and dissociation rate but also provided more diffusion channels for hydrogen, which contributed to the good de/rehydrogenation properties of MgH 2 .