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

Abstract

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 MgH2 with highly dispersed Ni nanoparticles by in-situ hydrogenolysis of nickelocene (NiCp2) in ball milling process. After ball milling under 4 MPa hydrogen atmosphere for 15 h, the MgH2–16.1 wt% NiCp2 sample exhibits a homogeneous morphology where the in-situ formed Ni nanoparticles with size of ~8 nm are highly dispersed in MgH2 matrix. During initial dehydrogenation, Ni would react with MgH2 to form Mg2Ni 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 MgH2 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 MgH2.