Supported metal sulphide nanoclusters studied by HAADF-STEM

The morphology of MoS2 and WS2 nanoclusters supported on high-surface area graphitic carbon was investigated using high angular annular dark field scanning transmission electron microscopy (HAADF-STEM). Most of the MoS2 (WS2) nanoclusters contain only a single S-Mo-S (S-W-S) layer and the most commonly encountered morphology is truncated triangular. This is in contrast to the hexagonal morphology of macroscopic MoS2 (WS2) crystals. When in addition to molybdenum (tungsten), nickel is also present, the regular nanoclusters are truncated to a larger extent, indicating that Ni has influenced the morphology by the formation of so-called Ni-Mo-S (Ni-W-S) structures. For these structures, the additional truncations are observed to lead to dodecahedral-like shapes.