(see Fig. 2 in the Supporting Information): a large heat of adsorption means greater stabilization of the adsorbed methane. The heat of adsorption of methane by europium-nitrate-dispersed SWNH at all density regions of adsorbed methane is greater than that of an as-grown SWNH by 40±90 meV.In conclusion, we have obtained the following results:d 1) A small amount of dispersed lanthanides strongly enhances the methane adsorption.d 2) Adsorbed methane molecules are stabilized by dispersed lanthanide nitrates on the SWNH.This enhancement effect of methane storage is only observed with carbon nanohorns (see Supporting Information). Currently we have only applied this method to as-grown SWNHs. However, enhancement of gas adsorption by charge transfer is promising as a means for achieving practical methane storage. ExperimentalObservation by STEM: The sample of europium-nitrate-dispersed SWNHs was put on a holey carbon grid disk and observed by a scanning transmission electron microscope (HD2000-UHV, Hitachi, 120 kV).Determination of Pore Volume of SWNHs: After pretreatment at 423 K and 1 mPa, the pore volume of the SWNHs was determined volumetrically by a nitrogen-adsorption isotherm at 77 K with a volumetric apparatus (Autosorb 1, Quantachrome) [2]. The nitrogen-adsorption isotherms were analyzed with the a s -method described by Sing [6]. The specific surface areas and micropore volumes of SWNH samples are shown in Table 1.Methane Adsorption: We measured the amount of methane adsorbed by a gravimetric method at 303 K by using an electric microbalance (Cahn 1100) [7] with a resolution of 0.1 lg. In order to remove adsorbed gases and water, a pretreatment was performed at a pressure of less than 1 mPa and temperature of 423 K for 2 h prior to the adsorption measurement.The adsorbed-methane density could not be obtained directly from the experiments. We therefore had to calculate it from the experimental adsorbed amount (surface excess mass). [8] We assumed that the adsorbed-methane density is given by [9] q ad = (C/V 0 ) + q bulk (1) where q ad (g L ±1 ) is the adsorbed-methane density, C (mg g ±1 ) is the experimental adsorbed-methane amount, V 0 (mL g ±1 ) is the pore volume of the SWNH, and q bulk is the density of methane in the bulk gas phase.Sample Preparation: The SWNH was synthesized by CO 2 laser ablation of graphite under Ar gas at 101 kPa [1]. Lanthanide nitrates were dispersed on the as-grown SWNH as lanthanide nitrate solution. The SWNH was mixed with an ethanolic lanthanide nitrate solution and this mixture was sonicated for five minutes. Finally, the mixture of lanthanide nitrate solution and SWNH was dried at room temperature for a week.Received Ternary Imides for Hydrogen Storage** By Zhitao Xiong, Guotao Wu, Jianjiang Hu, and Ping Chen*The demand for highly efficient solid-state hydrogen storage materials for the coming hydrogen economy has encouraged tremendous efforts in the development of novel systems such as complex chemical hydrides and carbonaceous materials.[1±4] Metal nitrides and imides, newc...

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The prospect of building a future energy system on hydrogen has stimulated much research effort in developing hydrogen storage technologies. One of the potential materials newly developed is sodium amidoborane (NaNH 2 BH 3 ) which evolves $7.5 wt% hydrogen at temperatures as low as 91 C. In this paper, two methods of synthesizing pure NaNH 2 BH 3 were reported. One method is by reacting NaH and ammonia borane in THF at low temperatures, and the other is by reacting NaNH 2 and ammonia borane in THF at ambient temperature. Non-isothermal testing on the thermolysis of solid NaNH 2 BH 3 showed that hydrogen evolution was composed of two exothermic steps. More than 1 equiv. H 2 was evolved rapidly at temperatures below 87 C. After evolving 2 equiv. H 2 , NaH was identified in solid products and coexisted with amorphous BN.

MgH(2) nanoparticles with a size of <3 nm were formed by direct hydrogenation of Bu(2)Mg inside the pores of a carbon scaffold. The activation energy for the dehydrogenation was lowered by 52 kJ mol(-1) compared to the bulk material, and a significantly reduced reaction enthalpy of 63.8 ± 0.5 kJ mol(-1) and entropy (117.2 ± 0.8 J mol(-1)) was found for the nanoconfined system.

H system have been studied by probing the pressure composition isotherms at different hydrogenation/dehydrogenation stages. The results of X-ray diffractometry and Fourier transform infrared spectroscopy show that LiNH 2 and a ternary imide with the composition Li 2 -Mg 2 (NH) 3 are reversibly formed and consumed in the hydrogen absorption/desorption processes. Chemical reactions have been proposed for hydrogen absorption and desorption, accordingly. The formation of solid solutions in the system is assumed based on structure and phase analysis.

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Stepwise solid‐state reaction between LiNH2 and LiAlH4 at a molar ratio of 2:1 is investigated in this paper. It is observed that approximately four H atoms are evolved from a mixture of LiNH2–LiAlH4 (2:1) after mechanical ball milling. The transformation of tetrahedral [AlH4]– in LiAlH4 to the octahedral [AlH6]3– in Li3AlH6 is observed after ball milling LiAlH4 with LiNH2. Al–N bonding is identified by using solid‐state 27Al nuclear magnetic resonance (NMR) measurements. The NMR data, together with the results of X‐ray diffraction and Fourier transform IR measurements, indicate that a Li–Al–N–H intermediate with the chemical composition of Li3AlN2H4 forms after ball milling. Heating the post‐milled sample to 500 °C results in the liberation of an additional four H atoms and the formation of Li3AlN2. More than 5 wt % hydrogen can be reversibly stored by Li3AlN2. The hydrogenated sample contains LiNH2, LiH, and AlN. The role of AlN in the reversible hydrogen storage over Li–Al–N–H is discussed.

Non-confined MgH2 nanoparticles of 4–5 nm diameter enable reversible storage of hydrogen up to 6.7 wt% at 30 °C.