Effect of high pressure sulfidation on the morphology and reactivity of MoS2 slabs on MoS2/Al2O3 catalyst prepared with citric acid

Structure and Quantification of Edge Sites of WS2/Al2O3 Catalysts Coupling IR/CO Spectroscopy and DFT Calculations

“…In previous works of our group on MoS 2 ‐based catalysts, distinct molar attenuation coefficient values were obtained for CO adsorbed on either M‐edge (ϵ CO /M‐edge) or S‐edge (ϵ CO /S‐edge) (Table II). These values allowed the quantification of MoS 2 sites of each edges and thus calculation of the S‐/M‐edge ratio that defines the morphology of the MoS 2 slabs . Recent work on sulfided Mo/Al 2 O 3 catalysts prepared with and without citric acid showed a good agreement between sulfided slab shape determined from IR/CO, and that observed on transmission electron microscope by STEM‐HAADF .…”

“…These values allowed the quantification of MoS 2 sites of each edges and thus calculation of the S-/M-edge ratio that defines the morphology of the MoS 2 slabs. [14] Recent work on sulfided Mo/Al 2 O 3 catalysts prepared with and without citric acid showed a good agreement between sulfided slab shape determined from IR/CO, and that observed on transmission electron microscope by STEM-HAADF. [17] This gave a proof by image of the morphological changes of the catalyst according to the preparation modes, and also underlined that IR/CO method allows to reach a representative average picture of the sulfided slab shapes.…”

“…Further, determination of the molar attenuation coefficients of ν(CO) band characteristics of the M‐edge and S‐edge sites allowed quantification of these two edges and thus assessment of the morphology of MoS 2 slabs . It was thus possible to demonstrate that the MoS 2 morphology (expressed by S edge /M edge ratio) varies with the preparation parameters (metal loading, chelating agent addition, support nature) and the sulfidation conditions . Recent observations of the sulfide catalysts by STEM HAADF confirmed the morphology of the MoS 2 slabs deduced from the spectroscopic analysis .…”

The Pivotal Role of Catalysis in France: Selected Examples of Recent Advances and Future Prospects.

“…Thus, complexing and chelating agents can interact more selectively with metallic promoters (Ni, Co) providing a better promotion during the sulfidation stage. However, the conditions in which such interactions take place, for instance pH or pressure of sulfidation, may generate different complexes with more or less impact. Non‐complexing agents interact in a much lesser extent with these promoters but can modify the support and precursor‐support interactions thus providing a better dispersion as well as an activation stage by delaying sulfidation…”

“…Note that quantification and structure of different basic sites in oxides could be recently extracted from the complex IR spectra of adsorbed CO 2 using 2D IR spectroscopic methods . NO and even more CO are the most suited molecules to probe surface of metal and sulfide phases since they inform on the nature, oxidation state, dispersion, defect, and morphology of these particles (Figure ) . However, the operating conditions can deeply modify the structure and the surface properties compared to fresh catalysts.…”