For the morphological study of the active MoS2 phase in supported hydrodesulfurization catalysts, the transmission electron microscopy (TEM) method suffers from contrast disturbance by the alumina support, and thus, top-view images of MoS2 slabs cannot be measured. HF etching was applied as an alumina-eliminating method for MoS2/Al2O3 catalysts and proved to be significant for TEM observation and statistical data processing of low-loading catalysts. High-resolution images of top-view MoS2 slabs were obtained after HF etching and MoS2 slabs were found to have different and irregular shapes. Vacancies at the edges of MoS2 slabs could be clearly detected. HF etching helped to identify that MoS2 slabs were preferentially basal-bonded on alumina independent of the precursors. When SBA-15 was used as support, basal-bonding dominated for catalyst with an oxidic precursor while edge-bonding for catalyst with a sulfidic precursor. Different MoS2 nanowires were observed after HF etching of MoS2/SBA-15 dependent on the precursors. (C) 2014 Elsevier Inc. All rights reserved.