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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