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摘要
A combination of quantum mechanics and molecular simulation were performed to investigate the adsorption capacity of pure hydrogen and helium and their mixture in silicon nanotubes (SiNTs). In the simulation, the gas-gas interactions were modelled as Lenard-Jones potential sphere. The binding energies between hydrogen and helium with the surface of SiNTs were obtained from ab initio calculations and fitted to Morse potential equation. The calculated binding energies were provided as an input in the MC simulation. First, ab initio calculations revealed stronger binding energy of SiNTs with H-2 compared with He. This is attributed to the different physicochemical properties and lower polarizability of He compared to H-2. Second, Monte Carlo simulation results were representative of higher magnitude of H-2 adsorption in all SiNTs than He in both pure and mixture systems. Most importantly, Our simulation results indicate that the gravimetric adsorption capacity of hydrogen in an equimolar mixture of H-2/He represent distinct improvement of 13.6%, 10.0%, and 8.5% in (5, 5), (7,7) and (9,9) SiNT at T = 50 K and P = 2 MPa compare to pure system. This suggests that with addition of helium to hydrogen system more efficient hydrogen adsorption can be achieved. Furthermore, MC calculations at the same theoretical level were performed for isodiameter CNT. By comparison of hydrogen adsorption increase in the mixture in SiNT and CNT, it is found that the percentage of hydrogen adsorption increase in the presence of helium as compared to pure system in (5, 5) SiNT is greater than that in isodiameter (8,8) CNT.
- 出版日期2012-5
