الفهرس 
Hydrogen StorageOnly 14 pages are availabe for public view
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Abstract
Hydrogen storage with high gravimetric density (GD) and volumetric density (V D) is a contemporary challenge in utilizing hydrogen energy. Nano-particles are ultimate suitable candidates for this purpose because of the large surface area which serves in storing hydrogen with high ca-pacity. Accumulation of these nano-particles is a common problem in nano-catalysis, nano-electronics and hydrogen storage.
Based upon its unique properties, graphene serves as a miraculous mate-rial with significant potential as a template to prevent the accumulation of nano particles.
In this work, nitrogen-doped-graphene is employed in order to prevent the accumulation of the small NiO clusters. Two types of NiO clusters are examined; namely, [NiO]2 and [NiO]3. The two clusters exhibited con-siderable ability to store hydrogen; [NiO]2 can store upto 6H2 molecules with average absorption energy of 0.27 eV, whileas [NiO]3 can store upto 3H2 molecules with average absorption energy of 0.45 eV. The obtained calculated results indicated that though the number of hydrogen molecules stored on [NiO]3 clusters is one-half the value for [NiO]2, yet the adsorption energy is 1.7 times greater. The charge transfer is reck-oned to be the governing mechanism underlying this increase.
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Moreover, first principles calculations based on DFT has been utilized to study the electronic properties of G and GNMs supported nickel clusters. The Ni6 cluster can be adsorbed onto the three templates (G, O GNM and N GNM) with binding energies of 0.96, 0.5 and 8.5 eV re-spectively.
The Ni6=G can store 9 H2 molecules with average binding energy 0.38 eV, and the magnetic moment of this cluster decreases Vs. adsorbing hydrogen molecules until its value vanishes. A charge transfer from Ni cluster to graphene sheet occurred that causes doping. In case of GNMs, Ni6 can store 8 H2 molecules with average binding energy 0.40 eV and 0.27 eV for Ni6=O GNM and Ni6=N GNM, respectively.
Consequently, the Ni13=G can store 9 H2 molecules with average binding energy 0.5 eV, as well as the magnetic moment of this cluster decreases Vs. adsorbing hydrogen.
Moreover, in case of GNMs, Ni13 can store 8 H2 molecules with av-erage binding energy 0.50 eV and 0.45 eV for Ni13=O GNM and Ni13=N GNM, respectively.