An alternative route for metal hydrogenation has been investigated: cold plasma hydrogen implantation on polyol-made transition metal nanoparticles. This treatment applied to a challenging system, Ni-H, induces a reordering of the metal lattice, and superstructure lines have been observed by both Bragg-Brentano and grazing incidence X-ray diffraction. The resulting intermetallic structure is similar to those obtained by very high-pressure hydrogenation of nickel and prompt us to suggest that plasma-based hydrogen implantation in nanometals is likely to generate unusual metal hydride, opening new opportunities in chemisorption hydrogen storage. Typically, almost isotropic in shape and about 30 nm sized hexagonal-packed Ni 2 H single crystals were produced starting from similarly sized cubic face-centred Ni polycrystals.