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.

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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.

The development of cost-effective and highly efficient catalysts is of scientific importance and practical need in the conversion and utilization of clean energy. One of the strategies fulfilling that demand is to achieve high exposure of a catalytically functional noble metal to reactants to maximize its utilization efficiency. We report herein that the single-atom alloy (SAA) made of atomically dispersed Pt on the surface of Ni particles (Pt is surrounded by Ni atoms) exhibits improved catalytic activity on the hydrolytic dehydrogenation of ammonia−borane, a promising hydrogen storage method for onboard applications. Specifically, an addition of 160 ppm of Pt leads to ca. 3-fold activity improvement in comparison to that of pristine Ni/CNT catalyst. The turnover frequency based on the isolated Pt is 12000 mol H2 mol Pt −1 min −1 , which is about 21 times the value of the best Ptbased catalyst ever reported. Our simulation results indicate that the high activity achieved stems from the synergistic effect between Pt and Ni, where the negatively charged Pt (Pt δ-) and positively charged Ni (Ni δ+ ) in the Pt-Ni alloy are prone to interact with H and OH of H 2 O molecules, respectively, leading to an energetically favorable reaction pathway.

Development of non-noble metal catalysts with similar activity and stability to noble metals is of significant importance in the conversion and utilization of clean energies.

Industrial ammonia synthesis catalyzed by Fe- and Ru-based catalysts is an energy-consuming process. The development of low-temperature active catalyst has been pursued for a century. Herein, we report that barium hydride (BaH2) can synergize with Co, leading to a much better low-temperature activity, i.e., the BaH2-Co/carbon nanotube (CNT) catalyst exhibits ammonia synthesis activity right above 150 °C; at 300 °C, it is 2 orders of magnitude higher than that of the BaO-Co/CNTs and more than 2.5-times higher than Cs-promoted Ru/MgO. Kinetic analyses reveal that the dissociative adsorption of N2 on the Co-BaH2 catalyst may not be the rate-determining step, as evidenced by the much smaller reaction order of N2 (0.43) and the lower apparent activation energy (58 kJ mol–1) compared with those of the unpromoted and BaO-promoted Co-based catalysts. BaH2, with a negative hydride ion, may act as a strong reducing agent, removing activated N from the Co surface and forming a BaNH species. The hydrogenation of the BaNH species to NH3 and BaH2 can be facilely carried out at 150 °C. The relayed catalysis by Co and BaH2 sites creates an energy-favored pathway that allows ammonia synthesis under milder conditions.

A new type of hydrogen storage materialnamely, calcium amidoborane ammoniate (Ca(NH2BH3)2·2NH3)is synthesized by reacting calcium amide and ammonia borane in a molar ratio of 1:2. Structural analyses show that this newly developed complex has a orthorhombic structure (space group Pna21) with unit-cell parameters of a = 18.673(3) Å, b = 5.2283(8) Å, c = 8.5748(12) Å, and V = 873.16(22) Å3. The presence of NH3 in the crystal lattice facilitates the formation of dihydrogen bonding between BH···HN, which is considerably shorter than that in calcium amidoborane (Ca(NH2BH3)2). As a consequence, the bond lengths of B−H and N−H are increased comparatively. Our experimental results show that more than 8 wt % hydrogen can be released from Ca(NH2BH3)2·2NH3 without borazine emission at 150 °C.