High resolution HAADF-STEM imaging of MoS2 nanometric phase encapsulated within different mesoporous supports.

Abstract : The HAADF-STEM mode is an excellent characterization tool for the investigation of the crystalline structure, morphology and spatial distribution of the active phases deposited or inserted in a support, due principally to the important difference between the atomic numbers of active phase and material support. In this general framework, the characterization of the MoS2 nanostructured phase deposited on a carbon support or on silica microspheres was the subject of several pioneering works. The aim of this work is to illustrate the benefits of using high resolution HAADF imaging for characterizing the morphology and the precise localization of MoS2 sulfide phase in various industrial supports. Using the HR mode, different types of localization of the MoS2 phase (in the walls or filling the pores of a SBA15 matrix) have been evidenced according to the preparation method, as well as the presence of small metallic clusters incorporated in the walls of the mesoporous network. In addition, combining the tomographic approach with the HAADF imaging allows a precisely description of the 3D distribution of the nanostructured phase on the support material. In this context, the distributions of sulfide nanoparticles within the disordered mesoporous networks of silica microspheres have been determined.