Hydrogen adsorption of Ti-decorated boron nitride nanotube: a density functional based tight binding molecular dynamics study

摘要

The hydrogen adsorption capabilities of Titanium functionalized single-walled BN nanotubes (BNNTs) with B-N defects was assessed by density-functional theory tight binding (DFTB) method. According to the DFTB molecular dynamics simulations, the BNNT structures were thermodynamically stable, the Ti atom once incorporated with the B-N defects present in BNNT (Ti-BNNT) protrudes to the external surface of the BNNT sidewall. The titanium atoms does not agglomerate to form any metal clusters. The results revealed that at 77 K and 10,000 KPa, the H-2-Ti-BNNT has a gravimetric hydrogen storage capacity above 7 wt% ideal for department of energy specifications. Further calculations suggest that the Ti-BNNT has a good affinity towards H-2 molecules and under low pressure of 500 KPa. The H-2 stays close to the Ti metal due to its partially cationic character with some H-2 attaching itself at the BNNT surface due to heteropolar bonding. H-2 atoms is physisorbed in analogous to or resembling something molecular near the Ti sites which gives rise to a significant storage capacity for H-2 in these modified BNNT.