A High-Resolution Transmission Electron Microscopy Study of the Influence of Fluorine on the Morphology and Dispersion of WS2 in Sulfided W/Al2O3 and NiW/Al2O3 Catalysts

The morphology of WS2 on sulfided tungsten and nickel–tungsten catalysts supported on alumina and fluorinated alumina, prepared from ammonium metatungstate and ammonium tetrathiotungstate, was investigated by means of high-resolution transmission electron microscopy. The sulfided catalysts prepared from ammonium metatungstate contain mainly single-layered WS2 slabs, while those prepared from ammonium tetrathiotungstate contain more multilayered WS2 slabs. Incorporation of nickel increases the stacking and stabilizes small WS2 crystallites. Fluorination of the alumina support increases the fraction of multilayered WS2 slabs and increases the WS2 slab diameter.