The adsorption and desorption of N 2 O on main-group ion-exchanged ZSM-5 was studied using temperature-programmed desorption （TPD） and density functional theory （DFT） calculations. TPD experiments were carried out to determine the desorbed temperature T max corresponding to the maximum mass intensity of N 2 O desorption peak and adsorption capacity of N 2 O on metal-ion-exchanged ZSM- 5s. The results indicated that T max followed a sequence of Ba 2＋ Ca 2＋ Cs ＋ K ＋ Na ＋ Mg 2＋ and the amount of adsorbed N 2 O on main-group metal cation followed a sequence of Ba 2＋ Mg 2＋ Ca 2＋ Na ＋ K ＋ Cs ＋ . The DFT calculations were performed to obtain the adsorption energy （E ads ）, which represents the strength of the interaction between metal cations and the N-end or O-end of N 2 O. The calculation results showed that the N-end of the N 2 O molecule was favorably adsorbed on ion-exchanged ZSM-5, except for Cs-ZSM-5. For alkali metal cations, the E ads of N 2 O on cations followed the order which was the same to that of T max ： Cs ＋ K ＋ Na ＋ . The calculated and experimental results consistently showed that the adsorption performances of alkaline-earth metal cations were better than those of alkali metal cations.
Bo ZhangYongan LuHong HeJianguo WangChangbin ZhangYunbo YuLi Xue
By means of first-principles density functional theory （DFT） calculations and molecular dynamics （MD） simulations, a series of coronal multi- walled silicon nanotubes （MWSiNTs） without or with hydrogen terminations are systematically identified. Notably, coronal MWSiNTs, where the interaction between the walls is preferable through covalent bonds rather than weak interaction, show better stability than CNT-like SiNTs. Moreover, they exhibit good elasticity with small Young＇s modulus. The investigation of the electronic structure demonstrates that they present metallic characteristics, which is in striking contrast to bulk silicon. Thus, the MWSiNTs may find important applications in electronic devices.
Yuanshuai ZhuZhibei QuGuilin ZhuangWulin ChenJianguo Wang
