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.

in 2015. His research focuses on exploring alkali and alkaline earthmetal hydrides and imides in catalytic ammonia decomposition and synthesis. Ping Chen is a professor and division head of Hydrogen Energy and Advanced Materials at the Dalian Institute of Chemical Physics. She received her BS, MS, and PhD degrees in chemistry in 1991, 1994, and 1997, respectively, from Xiamen University. Her primary research interests are material design and development for hydrogen storage and heterogeneous catalysis.

No abstract

The brown planthopper (BPH) and white-backed planthopper (WBPH) are the most destructive insect pests of rice, and they pose serious threats to rice production throughout Asia. Thus, there are urgent needs to identify resistance-conferring genes and to breed planthopper-resistant rice varieties. Here we report the map-based cloning and functional analysis of Bph6, a gene that confers resistance to planthoppers in rice. Bph6 encodes a previously uncharacterized protein that localizes to exocysts and interacts with the exocyst subunit OsEXO70E1. Bph6 expression increases exocytosis and participates in cell wall maintenance and reinforcement. A coordinated cytokinin, salicylic acid and jasmonic acid signaling pathway is activated in Bph6-carrying plants, which display broad resistance to all tested BPH biotypes and to WBPH without sacrificing yield, as these plants were found to maintain a high level of performance in a field that was heavily infested with BPH. Our results suggest that a superior resistance gene that evolved long ago in a region where planthoppers are found year round could be very valuable for controlling agricultural insect pests.

No abstract

The brown planthopper, Nilaparvata lugens, is a pest that threatens rice (Oryza sativa) production worldwide. While feeding on rice plants, planthoppers secrete saliva, which plays crucial roles in nutrient ingestion and modulating plant defense responses, although the specific functions of salivary proteins remain largely unknown. We identified an N. lugens-secreted mucin-like protein (NlMLP) by transcriptome and proteome analyses and characterized its function, both in brown planthopper and in plants. NlMLP is highly expressed in salivary glands and is secreted into rice during feeding. Inhibition of NlMLP expression in planthoppers disturbs the formation of salivary sheaths, thereby reducing their performance. In plants, NlMLP induces cell death, the expression of defense-related genes, and callose deposition. These defense responses are related to Ca 2+ mobilization and the MEK2 MAP kinase and jasmonic acid signaling pathways. The active region of NlMLP that elicits plant responses is located in its carboxyl terminus. Our work provides a detailed characterization of a salivary protein from a piercing-sucking insect other than aphids. Our finding that the protein functions in plant immune responses offers new insights into the mechanism underlying interactions between plants and herbivorous insects.

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 borohydride diammoniate (Ca(BH 4 ) 2 3 2NH 3 ), is synthesized by reacting calcium borohydride and 2 equiv of ammonia. Structural analyses show that this complex has an orthorhombic structure (space group Pbcn) with unit-cell parameters of a = 6.4160 A ˚, b=8.3900 A ˚, c = 12.7020 A ˚, and V = 683.75 A ˚3, in which Ca 2þ coordinates with four -BH 4 groups two -NH 3 groups. The presence of NH 3 in the crystal lattice facilitates the formation of B-H 3 3 3 H-N dihydrogen bonding. As a consequence, the bond lengths of B-H and N-H are increased with comparison to Ca(BH 4 ) 2 and NH 3 , respectively. Our experimental results show that more than 11.3 wt % hydrogen can be released exothermically from Ca(BH 4 ) 2 3 2NH 3 in a closed vessel at a temperature as low as 250 °C.