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Highly active dry methane reforming catalysts with boosted in situ grown Ni-Fe nanoparticles on perovskite via atomic layer deposition

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Science Advances  26 Aug 2020:
Vol. 6, no. 35, eabb1573
DOI: 10.1126/sciadv.abb1573
  • Fig. 1 Schematic comparison, SEM images, the correlation between the number of ALD cycles and the particle size/population, and x-ray photoelectron curves for the samples.

    (A) Conventional exsolution for LSTN and (B) corresponding SEM image of LSTN. Scale bar, 500 nm. (C) Topotactic exsolution via ALD for LSTN-20C-Fe and the corresponding SEM image of (D) LSTN-20C-Fe after reduction. Scale bar, 500 nm. (E) Exsolved particle population from 0 to 30 ALD cycles. (F) Particle size distribution from 0 to 30 ALD cycles. X-ray photoelectron curves of (G) LSTN after reduction and (H) LSTN-20C-Fe. a.u., arbitrary units.

  • Fig. 2 TEM of exsolved particles on LSTN parent material.

    (A) HAADF scanning TEM image of LSTN-20C-Fe. Scale bar, 40 nm. (B) EDS elemental map of La, Sr, Ti, Ni, and Fe. Scale bar, 40 nm. (C) HAADF scanning TEM image of LSTN-20C-Fe [orange rectangle in (A)] and the corresponding fast Fourier transformed pattern with zone axis = [100]. Scale bar, 5 nm. (D) HAADF scanning TEM image of the enlarged area [green rectangle in (A)]. Scale bar, 3 nm. (E) EDS elemental map of La, Sr, Ti, Ni, and Fe in the parent material of LSTN-20C-Fe [blue rectangle in (D)]. Scale bar, 1 nm.

  • Fig. 3 Schematics of the DFT model for the calculation of B-site metal cosegregation with an oxygen vacancy and cation exchange.

    (A) Cosegregation energy and (B) exchange energy comparison of various transition metals. (C) Schematics of the DFT calculations of the cation exchange and alloy formation.

  • Fig. 4 Catalytic properties for the DRM.

    (A) Reacted methane during the DRM reaction for LSTN, LSTN-10C-Fe, and LSTN-20C-Fe. (B) The activation energy of the methane reactivity calculated for LSTN, LSTN-10C-Fe, and LSTN-20C-Fe. (C) Arrhenius-type plots of reacted CH4 for bulk Ni and bulk Ni-Fe alloy catalysts. (D) The activation energy of the methane reactivity calculated for bulk Ni, bulk Ni-Fe 0.70, and bulk Ni-Fe 0.60. (E) Time dependence of CH4 reactivity and H2/CO ratio for LSTN-20C-Fe in DRM at 700°C.

  • Table 1 Nomenclature for the compounds based on the Fe-deposited LSTN system.

    CompoundAbbreviations
    La0.6Sr0.2Ti0.85Ni0.15O2.95 + reductionLSTN
    La0.6Sr0.2Ti0.85Ni0.15O2.95 + 5 cycles of Fe2O3
    deposition with ALD + reduction
    LSTN-5C-Fe
    La0.6Sr0.2Ti0.85Ni0.15O2.95 + 10 cycles of
    Fe2O3 deposition with ALD + reduction
    LSTN-10C-Fe
    La0.6Sr0.2Ti0.85Ni0.15O2.95 + 15 cycles of
    Fe2O3 deposition with ALD + reduction
    LSTN-15C-Fe
    La0.6Sr0.2Ti0.85Ni0.15O2.95 + 20 cycles of
    Fe2O3 deposition with ALD + reduction
    LSTN-20C-Fe
    La0.6Sr0.2Ti0.85Ni0.15O2.95 + 30 cycles of
    Fe2O3 deposition with ALD + reduction
    LSTN-30C-Fe
    1 cycle of deposition: exposing to Fe precursor for 360 s followed by
    oxidation to air.
  • Table 2 EDS elemental analysis on exsolved Ni-Fe alloy particles on LSTN-10C-Fe and LSTN-20C-Fe.

    Exsolved particleNi mole ratio of 1 mol Ni-Fe
    NumberLSTN-10C-FeLSTN-20C-Fe
    Site #10.780.54
    Site #20.620.66
    Site #30.650.61
    Site #40.690.61
    Site #50.690.64
    Site #60.700.54
    Site #70.710.58
    Average0.690.60
  • Table 3 Cosegregation (B-site metal with an oxygen vacancy) and Ni↔deposited metal exchange energies (in electron volts) on transition metal–doped La0.5Sr0.5TiO3(110).

    BulkM-Ov-M cosegregation energy (eV)Ni↔TM exchange energy (eV)
    Ti−0.12−3.20
    Cr−1.05−2.27
    Fe−1.45−1.87
    Mn−1.89−1.43
    Co−2.92−0.40
    Ni−3.320
    Cu−4.321.00

Supplementary Materials

  • Supplementary Materials

    Highly active dry methane reforming catalysts with boosted in situ grown Ni-Fe nanoparticles on perovskite via atomic layer deposition

    Sangwook Joo, Arim Seong, Ohhun Kwon, Kyeounghak Kim, Jong Hoon Lee, Raymond J. Gorte, John M. Vohs, Jeong Woo Han, Guntae Kim

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