Effect of boron substitution on hydrogen storage capacity of Li and Ti decorated naphthalene

Abstract

Interaction of molecular hydrogen with Li and Ti doped boron substituted naphthalene viz. C6B4H8Ti2 and C6B4H8Li2 has been studied using density functional theory (DFT) method. The C6B4H8Li2 complex can interact with maximum of four hydrogen molecules, whereas three H2 molecules are adsorbed on C10H8Li2 complex. The C6B4H8Ti2 complex can interact with maximum of eight hydrogen molecules. The gravimetric hydrogen uptake capacity of C6B4H8Ti2 and C6B4H8Li2 complex is found to be 6.85 and 5.55 wt % respectively, which is higher than that of unsubstituted C10H8Ti2 and C10H8Li2 complexes. The boron substitution has significantly affected the hydrogen adsorption energies. The H2 adsorption energy and Gibb's free energy corrected H2 adsorption energy are found to be more prominent after boron substitution. The C6B4H8Ti2 and C6B4H8Li2 complexes are more stable than the respective unsubstituted C10H8Ti2 and C10H8Li2 complexes due to their higher binding energies. According to the atom-centered density matrix propagation (ADMP) molecular dynamics simulations C6B4H8Li2 complex retain not a single adsorbed hydrogen molecule during the simulation at room temperature, whereas five hydrogen molecules at 300 K and eight at 100 K are remain absorbed on C6B4H8Ti2 complex. The C6B4H8Ti2 complex is found to be more promising material for hydrogen storage than C10B4H8Li2.