A DFT Investigation on Hydrogen Adsorption Based on Alkali-metal Organic Complexes

Using density functional theory calculation based on the B3LYP method, we have studied the interactions of H-2 molecules with alkali-metal organic complexes C6H6-nLin (n = 1 similar to 3), C6H5Na and C6H5K. A significant part of the electronic charge of M s orbital (Li 2s, Na 3s, K 4s) is donated to phenyl and is accommodated by H-2 bonding orbital. For all the complexes considered, each bonded alkali-metal atom can adsorb up to five H-2 in molecular form with the mean binding energy of 0.59, 0.55 and 0.56 eV/H-2 molecule for C6H6-nLin (n = 1 similar to 3), C6H5Na and C6H5K, respectively. The kinetic stability of these hydrogen-covered organometallic complexes is discussed in terms of energy gap between HOMO and LUMO. It is remarkable that these alkali-metal organic complexes can store up to 23.80 wt% hydrogen. Therefore, the complexes studied may be used as hydrogen storage materials.