Titanium Decorated Cyclo[18]carbon as a Promising Hydrogen Storage Material: A <scp>DFT</scp> Investigation

ABSTRACT Effective hydrogen (H 2 ) storage is essential for integrating renewable energy, decarbonizing various sectors, ensuring energy security and enabling the widespread use of H 2 as a clean fuel. For this purpose, we have investigated the H 2 storage properties of pristine and transition metals (TMs) decorated cyclo[18]carbon (C 18 nanoring) using density functional theory (DFT). The analysis reveals that pristine C 18 nanoring is not suitable as H 2 storage medium. To enhance the H 2 storage capacity, we have decorated it with TMs such as Titanium (Ti) and Zirconium (Zr), respectively. The calculated binding energies −3.98 eV for Ti and −4.41 eV for Zr with the C 18 nanoring, respectively, indicating strong interactions between them. This interactions is further confirmed by the change in structural parameters and electronic properties, including the density of states, energy gap, dipole moment and charge transfer. Furthermore, the Ti decorated C 18 nanoring is found to be a suitable medium for H 2 storage. The adsorption energy ( E ads ) of the first H 2 molecule on the Ti decorated C 18 nanoring meets the U.S. Department of Energy (DoE)'s criteria. With BSSE corrections taken into account, the Ti decorated C 18 nanoring can adsorb up to 14H 2 molecules within the DoE's limits, with an average E ads of −0.34 eV/H 2 and a desorption temperature of ~434 K. The calculated storage capacity of H 2 over Ti decorated C 18 nanoring is 9.65 wt%, which significantly exceeds the DoE's criteria. Ab initio molecular dynamics (AIMD) simulations confirm the thermal stability of Ti decorated C 18 nanoring at higher temperature. Overall, these findings suggest that Ti decorated C 18 nanoring has great potential for H 2 storage devices.