(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...

Ammonia synthesis under mild conditions is a goal that has been long sought after. Previous investigations have shown that adsorption and transition-state energies of intermediates in this process on transition metals (TMs) scale with each other. This prevents the independent optimization of these energies that would result in the ideal catalyst: one that activates reactants well, but binds intermediates relatively weakly. Here we demonstrate that these scaling relations can be broken by intervening in the TM-mediated catalysis with a second catalytic site, LiH. The negatively charged hydrogen atoms of LiH act as strong reducing agents, which remove activated nitrogen atoms from the TM or its nitride (TMN), and as an immediate source of hydrogen, which binds nitrogen atoms to form LiNH. LiNH further splits H heterolytically to give off NH and regenerate LiH. This synergy between TM (or TMN) and LiH creates a favourable pathway that allows both early and late 3d TM-LiH composites to exhibit unprecedented lower-temperature catalytic activities.

The safe and efficient storage of hydrogen is widely recognized as one of the key technological challenges in the transition towards a hydrogen-based energy economy. Whereas hydrogen for transportation applications is currently stored using cryogenics or high pressure, there is substantial research and development activity in the use of novel condensed-phase hydride materials. However, the multiple-target criteria accepted as necessary for the successful implementation of such stores have not yet been met by any single material. Ammonia borane, NH3BH3, is one of a number of condensed-phase compounds that have received significant attention because of its reported release of approximately 12 wt% hydrogen at moderate temperatures (approximately 150 degrees C). However, the hydrogen purity suffers from the release of trace quantities of borazine. Here, we report that the related alkali-metal amidoboranes, LiNH2BH3 and NaNH2BH3, release approximately 10.9 wt% and approximately 7.5 wt% hydrogen, respectively, at significantly lower temperatures (approximately 90 degrees C) with no borazine emission. The low-temperature release of a large amount of hydrogen is significant and provides the potential to fulfil many of the principal criteria required for an on-board hydrogen store.

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