Hydrogen storage by Ni-doped silicon carbide nanocage: A theoretical study

We have performed density-functional theory calculations (DFT) of the interaction of H-2 molecules with the silicon carbide fullerene-like cage (SiC)16 formed by Ni impurity and have compared the results with the bare systems without Ni. The effects of substituting a C or Si atom by a Ni atom on the geometrical structure and H-2 adsorption behavior were investigated. The result shows that a bare (SiC)16 fullerene-like cage is not suitable for hydrogen storage applications. We have shown that when a C is replaced by a Ni, the hydrogen adsorption energy is greatly enhanced. The adsorption of an H-2 molecule near a Ni atom on the surface of a Ni-doped silicon carbide fullerene-like cage is a factor of 10 times more intense than on the pure (SiC)16 cage. The substituted Ni atom is capable of adsorbing two hydrogen molecules at room temperature. The first H-2 is molecularly chemisorbed to the Ni-doped (SiC)16 with the binding energy of -0.737 eV, and the second H-2 is adsorbed to the system by physisorption with a binding energy of -0.179 eV, which is close to the desired range (0.20-0.6 eV per H-2) proposed by the U.S. Department of Energy. The present study shows the important effect of Ni atom doped on SiC nanocage and advances our knowledge of the molecular adsorption of hydrogen for practical hydrogen storage and might be helpful for fabricating nano-devices such as hydrogen storage materials.