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New progress in the study of ammonia decomposition by Dalian Institute of Chemicals
Recently, Guo Jianping, Department of Hydrogen Energy and Advanced Materials, National Laboratory for Clean Energy, Institute of Clean Energy, Chinese Academy of Sciences, found that the lithium imino compound (Li2NH) and iron nitride composites show excellent catalytic ammonia decomposition hydrogen production activity. Under the same reaction conditions, such as 450 ° C, the activity of the composite catalyst system is one order of magnitude higher than that of the supported iron-based catalyst or iron nitride. This research not only explains the role of alkali metal auxiliaries from a new perspective, but also provides new ideas for the design of high-efficiency catalysts, especially for the replacement of precious metal catalysts. The research paper was highly evaluated by reviewers and published online in the form of VIP (Very Important Paper) in the journal German Applied Chemistry (Angew. Chem. Int. Ed., doi: 10.1002/anie. 201410773).
Alkali metal auxiliaries play an important role in many catalytic processes. However, its mechanism of action is a long-standing controversial research topic. Through XRD, XAFS, isotope labeling and theoretical calculations, the research group proposed a new interpretation of the mechanism of action of lithium, that is, the properties of lithium imino group are different from the conventional electron donation (ie, electronic additives). It acts as a transport medium for ammonia and iron nitride to form a high nitrogen content ternary nitride Li3FeN2 intermediate (the induction effect of Li+ stabilizes the Fe-N bond), thereby changing the ammonia decomposition reaction path. Based on this finding, the research team further developed a new ammonia decomposition catalyst system, namely, a composite catalytic material system of lithium imino and a third-period transition metal or its nitride. In addition to antimony and zinc, other 3d elements combined with Li2NH showed a common, unprecedented high catalytic ammonia decomposition activity, and their activity sequence showed an interesting volcanic curve. It should be pointed out that the apex of the volcanic curve is located in the manganese element, which is significantly different from the activity law of the reported ammonia decomposition catalyst. More importantly, the catalytic ammonia decomposition of hydrogen nitride-imido lithium is even better than the highly active Ru/CNTs catalyst. The team led by Chen Ping, a researcher at Dalian Institute of Chemical Technology, has accumulated more than ten years of alkali metal (sub)amino compounds. This study is a new exploration in heterogeneous catalysis following the successful application of such compounds to hydrogen storage (Nature, 2002, 420, 302).
The work benefited from the joint research of Wang Junhu, a researcher at the Aerospace Catalysis and New Materials Research Office of Dalian Institute of Chemistry, and Wu Anan, an associate professor at Xiamen University, and was funded by the National Outstanding Youth Fund and the Natural Science Foundation.