Improved promoter effect in NiWS catalysts through a molecular approach and an optimized Ni edge decoration

• High intrinsic hydrogenation activity of Ni promoted WS2 catalyst.
• Efficient preparation method using molecular precursors of tungsten and nickel.
• Quasi hexagonal morphology of NiWS crystallites highlighted by HAADF-STEM.
• Quantification of Ni distribution by a multi-technique approach.
• Distribution of Ni promoter atoms at the edge tuned by the preparation method.

An efficient preparation method – based on the grafting and deposition of Ni and W molecular precursors onto partially dehydroxylated amorphous silica–alumina followed by a thermal treatment under H2S/H2 – generates supported NiWS catalysts exhibiting enhanced activities in toluene hydrogenation, by comparison with conventional samples, prepared from metallic salts. A careful analysis of these materials by IR, XPS, TEM, HAADF-STEM, together with DFT calculations, reveals that the improved activity probably originates from the lower sulfidation temperature of W that improves distribution of Ni–W mixed sites at the edges of NiWS crystallites. This provides an optimal compromise between intrinsic activity and surface concentration of active sites.

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