Structural changes of hydrotalcite-based Co-containing mixed oxides with calcination temperature and their effects on NOx adsorption: A combined experimental and DFT study

Yeji Choi, Hyeonjung Jung, Suji Kim, Jeong Woo Han, Ki Bong Lee

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7 Citations (Scopus)

Abstract

The structural changes of Co-containing hydrotalcite-based mixed oxides and their effects on the NOx adsorption were investigated using experiments and density functional theory (DFT) calculation. Co-Al and Co-Mg-Al hydrotalcite-like compounds were synthesized using the co-precipitation method and calcined at various temperatures between 550 and 850 °C. The X-ray diffraction and X-ray photoelectron spectroscopy results indicated that high-temperature calcination thermally decomposed the spinel phases, which were derived from the hydrotalcite-like compounds, to cobalt monoxide and decreased the amount of Co3+ ions on the surface of the mixed oxides. The NOx adsorption experiments performed at 150 °C presented that the calcination of the Co-Al and Co-Mg-Al hydrotalcite-like compounds at lower temperature was beneficial for the NOx uptake, and the Co-Mg-Al oxides calcined at 550 °C presented the highest NOx uptake (0.326 mmol/g) of all analyzed samples and also good cyclic stability and H2O resistance. The effects of the calcination temperature were further scrutinized using a DFT method and the results of the DFT calculation demonstrated that the adsorption of NO molecules was more favorable over the spinel phases than over the cobalt monoxide. This work is the first study to perform the DFT calculation on the NOx adsorption over the mixed oxides derived from the hydrotalcite-like compounds, and our works are expected to be helpful for developing high-performance NOx adsorbents by identifying the advantageous structures of the mixed oxides for NOx adsorption.

Original languageEnglish
Article number135209
JournalChemical Engineering Journal
Volume437
DOIs
Publication statusPublished - 2022 Jun 1

Bibliographical note

Funding Information:
This work was supported by the Super Ultra Low Energy and Emission Vehicle Engineering Research Center (grant number NRF-2016R1A5A1009592 ) of the National Research Foundation of Korea funded by the Korean government Ministry of Science and ICT.

Publisher Copyright:
© 2022 Elsevier B.V.

Keywords

  • DFT calculation
  • Layered double hydroxide
  • Lean NO trap
  • NO storage-reduction
  • Nitrite route
  • Spinel

ASJC Scopus subject areas

  • General Chemistry
  • Environmental Chemistry
  • General Chemical Engineering
  • Industrial and Manufacturing Engineering

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