Nickel is a good catalyst for the dissociation of molecular hydrogen to atomic form, but suffers from a negligible hydrogen storage capacity (similar to 10(-4) wt% at 25 degrees C and 1 atm). The current investigation pertains to the enhancement in the reversible hydrogen storage capacity of Ni via storage in molecular form; thus utilizing a recently developed multi-mode storage philosophy. Ni nano hollow spheres (NiHS) have been synthesized using hydro thermal method (outer diameter of similar to 300 nm and shell thickness similar to 30 nm). Pressure composition-isotherms and temperature programmed desorption curves have been used to characterize the hydrogen storage capacity and to establish the reversibility of the process. An enhancement in the reversible storage capacity by a factor of 7 x 10(3) (7,00,000%) is obtained at 25 degrees C and 150 bar pressure. The capacity is further enhanced to 0.91 wt% hydrogen by utilizing a pressure of 300 bar. Ni plays a dual catalytic role in the absorption and desorption process. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.