Magnifying the morphology change induced by a nickel promoter in tungsten(IV) sulfide industrial hydrocracking catalyst : a HAADF-STEM and DFT study.

Abstract : Changes in the two-dimensional (2D) morphology of nonpromoted WS2 and Ni-promoted WS2 (NiWS) catalytically active nanolayers supported on amorphous silica-alumina (ASA) are revealed by aberration-corrected scanning transmission electron microscopy and rationalized by density functional theory calculations. The presence of the Ni atoms modifies the triangular shape of nonpromoted WS2/ASA nanolayers into a more hexagonal one for NiWS/ASA by stabilizing the S edge more strongly than the W edge. The higher catalytic activity induced by the addition of the promoter confirms the relevance of such a morphology effect for industrial catalysts.