The Effect of Natural Silica from Rice Husk Ash and Nickel as a Catalyst on the Hydrogen Storage Properties of MgH2

The characteristics of MgH2 as a hydrogen storage material in this study were observed by varying the composition of the catalyst. The added catalyst was a dual catalyst, namely nickel and natural silica extracted from rice husk ash with a composition of MgH2 + 10 wt% SiO2 + 10 wt% Ni (Sample A), then MgH2 + 5 wt% SiO2 + 10 wt% Ni (Sample B), and MgH2 + 10 wt% SiO2 + 5 wt% Ni (sample C). The samples were prepared using the high energy ball milling (HEBM). The results showed that the natural silica extracted from rice husk ash (hereafter called "RHA") can be used as a catalyst in MgH2. Then, simultaneous use of nickel with silica as dual catalyst has shown the improvement in the hydrogen storage characteristics such as temperature and desorption time. The results of this study also indicate that the composition of the catalyst affects the particle size, although the time and milling treatment are the same. Furthermore, the particle size affects the characteristics of MgH2 as a hydrogen storage material. Apart from particle size, there are other parameters that influence the characteristics of MgH2, which appear during the sample preparation process such as impurity and agglomeration phases, all of which are closely related to the composition and type of catalyst used and the milling treatment applied to the sample. The 10 hours milling time used in this study has succeeded in reducing the sample to nano size. The Mg-based materials which have a nanostructure will have a larger contact area for the hydrogen reaction. The diffusion distance during the hydrogen absorption reaction also becomes smaller so as to improve the kinetic and thermodynamic characteristics of MgH2.