Research ArticleAPPLIED SCIENCES AND ENGINEERING

Dissociating stable nitrogen molecules under mild conditions by cyclic strain engineering

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Science Advances  01 Nov 2019:
Vol. 5, no. 11, eaax8275
DOI: 10.1126/sciadv.aax8275
  • Fig. 1 The reactivity of N2 dissociation.

    (A) Nitrogen content in the as-prepared nitrogenated GNP as a function of time. (B) The corresponding Avrami equation of reaction kinetics. C is the concentration of N, and CL the limiting concentration of N. (C) The nitrogen consumption (Vconsumed) as a function of different charging pressures. (D) The poisoning experiments. Triethanolamine (TEA), glass powder, KCl, and Na2S were separately added as interference. (E) The self-nitrogenating phenomenon of the Fe ball is characterized by the N+ content on the surface of the Fe balls. The N+ content was determined by time-of-flight secondary ion mass spectrometry. ppm, parts per million.

  • Fig. 2 The transfer experiments.

    (A) XRD patterns of the nitrogenated Fe [Fe(N*)] and its mixture with GNP (Fe + GNP). (B) The radial distribution function, determined by EXAFS. (C) Mossbauer spectroscopy results. (D) The transfer process of N from nitride Fe─N to organic C─N, recorded by high-resolution observation of N 1s. a.u., arbitrary units.

  • Fig. 3 Theoretical analysis of the formation and adsorption energy as a function of applied strain.

    (A) The Fe bulk model. (B) The Fe (110) surface model. The relaxed model is fully relaxed. The unrelaxed model adopts the same Poisson’s responses as those in the relaxed model except that the atom positions were not relaxed. A lower energy value (ΔE) corresponds to stronger adsorption of N atoms on the Fe substrate. A higher ΔE value indicates easier segregation of nitrogen atoms from the corresponding Fe system.

  • Fig. 4 N2 dissociation via cyclic strain engineering.

    The repeated collisions of the Fe balls result in the activation of the surface. The originally flat and passivated surfaces are converted into nanocrystalline structures with highly active sites. N2 dissociation occurs on the Fe atoms of the activated surface. The shock of compression reduces the N* adsorption energy, and the N* atoms are detached from the surface. The vacant sites on the activated surface will adsorb new N* atoms at the strain-free stage, and the cyclic strain process will repeat until the collisions stop.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/11/eaax8275/DC1

    Supplementary Materials and Methods

    Supplementary Text

    Fig. S1. Comparison of the as-prepared samples in N2 and Ar.

    Fig. S2. GNPs after different nitrogenation times.

    Fig. S3. GNPs after different nitrogenation times.

    Fig. S4. Studies of the rotation speed of ball milling, the loading amount of graphite, the critical reaction pressure, and temperature of the ball-mill container.

    Fig. S5. Ball milling by ZrO2 balls.

    Fig. S6. The poisoning experiments.

    Fig. S7. The self-nitrogenating protection phenomenon of Fe balls.

    Fig. S8. The transfer experiments.

    Fig. S9. Extension to other carbon materials.

    Table S1. Elemental analysis of the GNP.

  • Supplementary Materials

    This PDF file includes:

    • Supplementary Materials and Methods
    • Supplementary Text
    • Fig. S1. Comparison of the as-prepared samples in N2 and Ar.
    • Fig. S2. GNPs after different nitrogenation times.
    • Fig. S3. GNPs after different nitrogenation times.
    • Fig. S4. Studies of the rotation speed of ball milling, the loading amount of graphite, the critical reaction pressure, and temperature of the ball-mill container.
    • Fig. S5. Ball milling by ZrO2 balls.
    • Fig. S6. The poisoning experiments.
    • Fig. S7. The self-nitrogenating protection phenomenon of Fe balls.
    • Fig. S8. The transfer experiments.
    • Fig. S9. Extension to other carbon materials.
    • Table S1. Elemental analysis of the GNP.

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