Research ArticleChemistry

Methanol conversion on borocarbonitride catalysts: Identification and quantification of active sites

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Science Advances  24 Jun 2020:
Vol. 6, no. 26, eaba5778
DOI: 10.1126/sciadv.aba5778
  • Fig. 1 Schematic illustration of the preparation procedure of BCNNTs (left) and the proposed reaction pathways (right) for methanol conversion.

  • Fig. 2 Structure characterization of BCNNTs.

    (A to C) TEM and HRTEM images and (D to G) energy-filtered TEM elemental mapping images of BCNNTs.

  • Fig. 3 Catalytic activity measurements and comparisons.

    (A) Methanol conversion activity of BCNNTs-360°C as a function of reaction time. (B) Methanol conversion activity of BN, OCNT, BCNNTs-320°C, and B4C catalysts (reaction conditions: 1 kPa of methanol; 8 kPa of O2, 573 K, 100 mg of catalysts, balance He). (C) Steady-state catalytic activities (573 K) of BCNNT catalysts with different oxygen contents (calcination temperature).

  • Fig. 4 Identification and quantification of active sites over BCNNT-catalyzed methanol conversion reaction.

    (A) Schematic illustration for methanol ODH and dehydration reaction on active sites. (B) DME formation rate (■) as a function of the surface concentration of ─COOH. (C) Correlation between experimental (rFA) and simulated (rFA = TOF(C═O)·[C═O] + TOF(B─OH)·[B─OH]) FA formation rate (★). (D) Simulated FA formation rate as a function of the surface concentration of ─C═O (●) and ─B─OH (▲). Reaction conditions: 1 kPa of methanol, 8 kPa of O2, 573 K, 100 mg of catalysts, balance He.

  • Fig. 5 Mechanism of methanol ODH reactions on B─OH site.

    (A) DRIFTS of BCNNTs-340°C. (B) IR signal intensity at 930 cm−1 (─B─O) of BCNNTs-340°C upon the introduction of O2 and methanol during in situ DRIFT measurements. (C) B K-edge and (D) N K-edge XAS of fresh BCNNTs and the samples after reaction with O2 and methanol, respectively.

  • Fig. 6 DFT analysis for BCNNT catalysis.

    (A) Schematic of the computational models of C0, C1, C1*, C2, and C2*. Gray (black), pink, red, blue, and white balls represent C, B, O, N, and H atoms, respectively. (B) Calculated ΔGB-O-O-B for the rate-determining step on C0, C1, C1*, C2, and C2*. (C) Calculated free-energy diagram for ODH reduction over C2 system. The insets are the optimized structures of the intermediates along the reaction path. (D) Calculated projected DOS for 2p orbitals of the B of C0, C1, and C2 systems. All energy levels are relative to the Fermi level for each system, which is set to zero. The energy levels with the p-band center of C0, C1, and C2 are highlighted in black, red, and blue dashed lines, respectively.

  • Table 1 Catalytic activity comparison.

    Catalytic activity of BCNNTs compared with that of metal-based catalysts.

    No.CatalystsT (K)Mass (g)PO2/PCH3OHConversion (%)Selectivity (FA, %)Reference
    1BCNNTs5730.108:12954This work
    2Au-NbMCF5730.128:4206127
    3TiO2-300C5730.0255:128728
    4V-Mg-O5731:1309929
    5MoOx/SiO24763.147:6208930
    6V2O5/TiO24330.2016:5416131
    7Cu/SBA-35230.022:184732
    8MoOx-Fe2O349810:1909233
    9ZrMCF5730.128:461527
    10Ag/SiO29132.00.51:1968934

Supplementary Materials

  • Supplementary Materials

    Methanol conversion on borocarbonitride catalysts: Identification and quantification of active sites

    Xuefei Zhang, Pengqiang Yan, Junkang Xu, Fan Li, Felix Herold, Bastian J. M. Etzold, Peng Wang, Dang Sheng Su, Sen Lin, Wei Qi, Zailai Xie

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