Bis(cyclopentadienyl) nickel II is one of the best precursors of nickel catalyst which remarkably improved the hydrogen absorption-desorption of Mg-MgH2 system. The X-ray photoelectron spectroscopy (XPS) and Furrier Transformed Infrared Spectroscopy (FTIR) analyses revealed that bis (cyclopentadienyl) nickel II decomposed into metallic nickel during ball milling with MgH2. The nickel thus formed has homogeneously doped over the Mg-MgH2 surface. The Ni-doped Mg-MgH2 have shown the excellent catalytic effect on hydrogen absorption-desorption. The catalyzed MgH2 could desorb hydrogen below 225 degrees C (T-onset) under Ar flow, and absorb hydrogen at 50 degrees C under 1.5 MPa H-2 pressure. The hydrogen absorption-desorption temperatures are remarkably decreased as compared to the uncatalyzed Mg-MgH2 system under the identical experimental conditions. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.