A DFT study of interaction of hydrogen molecules and (5,5) carbon nanotube with bioinspired functionalization

All electron density functional theory (DFT) calculations have been carried out for calcium-doped porphyrin-incorporated (5, 5) carbon nanotube (Ca-PICNT) to investigate the formation energies, electronic properties of this system, and its application in hydrogen storage. It is found that the incorporation of porphyrin ring in carbon nanotube led to a decreased value of the highest occupied molecular orbital and lowest unoccupied molecular orbital gap and a strong binding of Ca over nanotube and consequently resulted to a drastic reduction of clustering of Ca atom over Ca-decorated carbon nanotube. The Ca-PICNT can bind a maximum of 4H2 with binding energy value of 0.105 eV per H2 molecule. Charge decomposition analysis indicated that the mode of hydrogen storage is via coulomb-electrostatic force, which is further supported by the natural bond orbital and partial density-of-states studies.