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

Abstract

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.