In situ incorporation of highly dispersed nickel and vanadium trioxide nanoparticles in nanoporous carbon for the hydrogen storage performance enhancement of magnesium hydride

Slow hydrogen absorption-desorption kinetics and high thermal stability hinder the industrial application of Mg/MgH2 systems. In order to overcome these drawbacks, the in situ incorporation of highly dispersed nickel and vanadium trioxide nanoparticles in nanoporous carbon ((Ni-V2O3)@C) was introduced to enhance the hydrogen storage performance of Mg/MgH2. It was found that the 10 wt% (Ni-V2O3)@C-containing sample demonstrated excellent hydrogen storage performance. The 10 wt% (Ni-V2O3)@C-containing sample could uptake hydrogen at room temperature, and its initial hydrogenation temperature was reduced by 100 °C as compared to that of pristine MgH2. Moreover, this system could absorb 5.50 wt% of H2 at 25 °C and release 6.05 wt% of H2 at 275 °C in 10 min. In addition, the hydrogenation and dehydrogenation activation energies of the 10 wt% (Ni-V2O3)@C-containing sample were calculated as 42.1 kJ·mol−1 and 84.6 kJ·mol−1, respectively, which were 46.8 kJ·mol−1 and 51.6 kJ·mol−1 lower than those of pristine MgH2, respectively. Mechanism analysis results revealed that V2O3 was partially converted into VO during milling with MgH2, and Ni reacted with Mg to form in situ Mg2Ni after the first dehydrogenation. The in situ Mg2Ni/Mg2NiH4 coating around Mg/MgH2 acted as a “hydrogen pump” to drive hydrogen diffusion and dissociation, and the presence of C inhibited the agglomeration of Mg/MgH2 particles. Therefore, the addition of (Ni-V2O3)@C was found to be a good strategy to improve the hydrogen storage performance of MgH2.