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.