title: Lithium imide synergy with 3d transition-metal nitrides leading to unprecedented catalytic activities for ammonia decomposition.
abstract: Alkali metals have been widely employed as catalyst promoters; however, the promoting mechanism remains essentially unclear. Li, when in the imide form, is shown to synergize with 3d transition metals or their nitrides TM(N) spreading from Ti to Cu, leading to universal and unprecedentedly high catalytic activities in NH3 decomposition, among which Li2NH-MnN has an activity superior to that of the highly active Ru/carbon nanotube catalyst. The catalysis is fulfilled via the two-step cycle comprising: 1) the reaction of Li2NH and 3d TM(N) to form ternary nitride of LiTMN and H2, and 2) the ammoniation of LiTMN to Li2NH, TM(N) and N2 resulting in the neat reaction of 2 NH3⇌N2+3 H2. Li2NH, as an NH3 transmitting agent, favors the formation of higher N-content intermediate (LiTMN), where Li executes inductive effect to stabilize the TM-N bonding and thus alters the reaction energetics.
authors.affiliation: Collaborative Innovation Center of Chemistry for Energy Materials, State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (P. R. China) http://www.imide.dicp.ac.cn.
authors.forename: Jianping
authors.initials: J
authors.lastname: Guo
authors.forename: Peikun
authors.initials: P
authors.lastname: Wang
authors.forename: Guotao
authors.initials: G
authors.lastname: Wu
authors.forename: Anan
authors.initials: A
authors.lastname: Wu
authors.forename: Daqiang
authors.initials: D
authors.lastname: Hu
authors.forename: Zhitao
authors.initials: Z
authors.lastname: Xiong
authors.forename: Junhu
authors.initials: J
authors.lastname: Wang
authors.forename: Pei
authors.initials: P
authors.lastname: Yu
authors.forename: Fei
authors.initials: F
authors.lastname: Chang
authors.forename: Zheng
authors.initials: Z
authors.lastname: Chen
authors.forename: Ping
authors.initials: P
authors.lastname: Chen
keywords: ammonia decomposition; electronic promoter; heterogeneous catalysis; lithium imide; nitrides