In situ formation of multiple catalysts for enhancing the hydrogen storage of MgH2 by adding porous Ni3ZnC0.7/Ni loaded carbon nanotubes microspheres

MgH2 is considered one of the most promising hydrogen storage materials because of its safety, high efficiency, high hydrogen storage quantity and low cost characteristics. But some shortcomings are still existed: high operating temperature and poor hydrogen absorption dynamics, which limit its application. Porous Ni3ZnC0.7/Ni loaded carbon nanotubes microspheres (NZC/[email protected]) is prepared by facile filtration and calcination method. Then the different amount of NZC/[email protected] (2.5, 5.0 and 7.5 wt%) is added to the MgH2 by ball milling. Among the three samples with different amount of NZC/[email protected] (2.5, 5.0 and 7.5 wt%), the MgH2-5 wt% NZC/[email protected] composite exhibits the best hydrogen storage performances. After testing, the MgH2-5 wt% NZC/[email protected] begins to release hydrogen at around 110 °C and hydrogen absorption capacity reaches 2.34 wt% H2 at 80 °C within 60 min. Moreover, the composite can release about 5.36 wt% H2 at 300 °C. In addition, hydrogen absorption and desorption activation energies of the MgH2-5 wt% NZC/[email protected] composite are reduced to 37.28 and 84.22 KJ/mol H2, respectively. The in situ generated Mg2NiH4/Mg2Ni can serve as a "hydrogen pump" that plays the main role in providing more activation sites and hydrogen diffusion channels which promotes H2 dissociation during hydrogen absorption process. In addition, the evenly dispersed Zn and MgZn2 in Mg and MgH2 could provide sites for Mg/MgH2 nucleation and hydrogen diffusion channel. This attempt clearly proved that the bimetallic carbide Ni3ZnC0.7 is a effective additive for the hydrogen storage performances modification of MgH2, and the facile synthesis of the Ni3ZnC0.7/[email protected] can provide directions of better designing high performance carbide catalysts for improving MgH2.