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Nitrogen reduction reaction on small iron clusters supported by N-doped graphene:A theoretical study of the atomically precise active-site mechanism

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Nano Research 2020年第8期13卷 2280-2288页

作者： Chaonan Cui Hongchao Zhang Zhixun Luo Beijing National Laboratory for Molecular Sciences(BNLMS) State Key Laboratory for Structural Chemistry of Unstable and Stable SpeciesInstitute of ChemistryChinese Academy of SciencesBeijing100190China University of Chinese Academy of Sciences Beijing100049China

Nonprecious metal catalysts are known of significance for electrochemical N2 reduction reaction(NRR)of which the mechanism has been illustrated by ongoing investigations of single atom catalysis.However,it remains challenging to fully understand the size-dependent synergistic effect of active sites inherited in substantial nanocatalysts.In this work,four types of small iron clusters Fen(n=1–4)supported on nitrogen-doped graphene sheets are constructed to figure out the size dependence and synergistic effect of active sites for NRR catalytic activities.It is revealed that Fe3 and Fe4 clusters on N4G supports exhibit higher NRR activity than single-iron atom and iron dimer clusters,showing lowered limiting potential and restricted hydrogen evolution reaction(HER)which is a competitive reaction channel.In particular,the Fe4-N4G displays outstanding NRR performance for“side-on”adsorption of N2 with a small limiting potential(−0.45 V).Besides the specific structure and strong interface interaction within the Fe4-N4G itself,the high NRR activity is associated with the unique bonding/antibonding orbital interactions of N-N and N-Fe for the adsorptive N2 and NNH intermediates,as well as relatively large charge transfer between N2 and the cluster Fe4-N4G.

关键词： N2 reduction reaction(NRR) iron clusters cluster catalysis active-site mechanism density functional theory(DFT)

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Preparation of Nano-Sized γ-Al_2O_3 Supported iron Catalyst for Fischer-Tropsch Synthesis by Solvated Metal Atom Impregnation Methods

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Journal of Natural Gas Chemistry 2007年第1期16卷 46-52页

作者： Lihua Yu Xiaoxiang Zhang Zongjie Du Da Wang Shurong Wang Shihua Wu Department of Chemistry Nankai University Tianjin 300071 China

Two types of small iron clusters supported on γ-Al2O3-RT（dehydroxylated at room temperature） and γ-Al2O3-800 （dehydroxylated at 800 ℃） were prepared by solvated metal atom impregnation （SMAI） techniques. The iron atom precursor complex, bis（toluene）iron（0） formed in the metal atom reactor, was impregnated into γ-Al2O3 having different concentrations of surface hydroxyl groups to study the effect of surface hydroxylation on the crucial stage of iron cluster formation. Catalysts prepared in this way were characterized by TEM, Mǒssbauer, and chemisorption measurements, and the results show that higher concentration of surface hydroxyl groups of γ-Al2O3-RT favors the formation of more positively charged supported iron cluster Fen/γ-Al2O3-RT, and the lower concentration of surface hydroxyl groups of γ-Al2O3-800 favors the formation of basically neutral supported iron cluster Fen/γ-Al2O3-800. The measured results also indicate that the higher concentration of surface hydroxyl groups causes the rapid decomposition of precursor complex, bis（toluene）iron（0）, and favors the formation of relatively large iron cluster. Consequently, these two types of catalysts show different catalytic properties in Fischer-Tropsch reaction. The catalytic pattern of Fen/γ-Al2O3-RT in F-T reaction is similar to that of the unreduced γ-Fe2O3 and that of Fen/γ-Al2O3-800 is similar to that of the reduced α-Fe2O3.

关键词： iron clusters solvated metal atom impregnation iron atom precursor complex FischerTropsch synthesis alumina supported catalyst

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Preparation of Highly Dispersed Supported Metal Catalysts via Solvated Metal Atom Impregnation ( V) --The Effects of Hydroxyl Group on the Surface Concentrations of SiO2 on the Properties of Supported Fe clusters

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Chemical Research in Chinese Universities 1990年第1期6卷 47-55页

作者： Wu Shihua, Yang Shujun, Huang Weiping and Wang Xukun (Department of Chemistry and Institute of Elemento-Organic Chemistry, Nankai University, Tianjin)

Two kinds of small iron clusters supported on SiO2-200 (dehydroxylated at 200℃ and SiO2-600 (de-hydroxylated at 600℃) were prepared by Solvated Metal Atom Impregnation (SMAI) techniques. The iron atom precursor complex, bis (toluene) iron(0) formed in the metal atom reactor, was impregnated into SiO2 having different concentrations of surface hydroxyl groups to study the effect of surface hydroxylation on the crucial stage of iron cluster formation. Catalysts prepared in this way were characterized by THM, Mosbauer and chemisorption measurements, and the resules show that higher concentration of surface hydroxyl groups of SiO2-200 favours the formation of more positively charged support iron cluster Fen/SiO2-200 and the lower concentration of surface hydroxyl groups of SiO2-600 favours the formation of basically neutral supported iron cluster Fe2/SiO2-600. The measured results also indicate that the higher concentration of surface hydroxyl groups causes the precursor complex,bis(toluene) fron(0), to decompose more rapidly, and favours the formation of relatively large iron cluster. As a consequence, these two kinds of catalysts show different catalytic properties in Fischer-Tropsch reaction. The catalytic pattern of Fe/SiO2-200 in F-T reaction is similar to that of the unreduced a-Fe2O2, while Fe2/SiO2 -600 is similar to that of reduced α-Fe2O2.

关键词： iron clusters Solvated metal atom impregnation. iron atom precursor complex

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