Enhanced hydrogen desorption properties of MgH2 by highly dispersed Ni: The role of in-situ hydrogenolysis of nickelocene in ball milling process

Magnesium hydride is a promising hydrogen storage material and how to improve its sorption kinetics is one of challenges in practical applications. In this paper, a new approach is proposed to catalyze MgH 2 with highly dispersed Ni nanoparticles by in-situ hydrogenolysis of nickelocene (NiCp 2 ) in ball milling process. After ball milling under 4 MPa hydrogen atmosphere for 15 h, the MgH 2 –16.1 wt% NiCp 2 sample exhibits a homogeneous morphology where the in-situ formed Ni nanoparticles with size of ~8 nm are highly dispersed in MgH 2 matrix. During initial dehydrogenation , Ni would react with MgH 2 to form Mg 2 Ni which inherits the configuration of its high dispersion. In the subsequent hydrogen absorption and desorption cycles, the much fine and highly dispersed Ni-based catalytic phase contributes to the superior hydrogen desorption kinetics of MgH 2 with a high-capacity retention rate of ~96% after 50 cycles. This work demonstrates that the in-situ formation of highly dispersed catalytic species is beneficial for improving hydrogen storage properties of MgH 2 .