Improved hydrogen storage properties of MgH2 by the addition of FeS2 micro-spheres.

The sulfide catalyst is a subject of great interest in developing a MgH2 system as a potential hydrogen storage medium. In this work, FeS2 micro-spheres were successfully prepared by the surfactant-assisted solvothermal method, and later were ball milled with MgH2 to fabricate the MgH2-16.7 wt% FeS2 composite. FeS2 addition could dramatically improve both the hydrogenation and dehydrogenation kinetics, and lower the dehydrogenation temperature of MgH2 as well. The MgH2-16.7 wt% FeS2 composite could absorb 3.71 wt% H2 at 423 K, which is 3.59 times as high as that of the as-milled pure MgH2. The composite started to release hydrogen at 569 K, and it could release 1.24 wt% H2 at 573 K within 1400 s. However, pure MgH2 could only release 0.18 wt% H2 under the identical conditions. Furthermore, the activation energy of hydrogen desorption was reduced to 68.94 kJ mol-1. FeS2 addition also altered the rate-controlling steps and facilitated the H diffusion of MgH2 in the hydrogen absorption process. The synergistic catalytic effects of the in situ formed Fe active species and MgS may contribute to the enhanced hydrogen storage properties of MgH2.