Metallized siligraphene nanosheets (SiC7) as high capacity hydrogen storage materials

Abstract

<p>A planar honeycomb monolayer of siligraphene (SiC₇) could be a prospective medium for clean energy storage due to its light weight, and its remarkable mechanical and unique electronic properties. By employing van der Waals-induced first principles calculations based on density functional theory (DFT), we have explored the structural, electronic, and hydrogen (H₂) storage characteristics of SiC₇ sheets decorated with various light metals. The binding energies of lithium (Li), sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), scandium (Sc), and titanium (Ti) dopants on a SiC₇ monolayer were studied at various doping concentrations, and found to be strong enough to counteract the metal clustering effect. We further verified the stabilities of the metallized SiC₇ sheets at room temperature using ab initio molecular dynamics (MD) simulations. Bader charge analysis revealed that upon adsorption, due to the difference in electronegativity, all the metal adatoms donated a fraction of their electronic charges to the SiC₇ sheet. Each partially charged metal center on the SiC₇ sheets could bind a maximum of 4 to 5 H₂ molecules. A high H₂ gravimetric density was achieved for several dopants at a doping concentration of 12.50%. The H₂ binding energies were found to fall within the ideal range of 0.2-0.6 eV. Based on these findings, we propose that metal-doped SiC₇ sheets can operate as efficient H₂ storage media under ambient conditions.</p>