Investigation of MoS 2 on γ-Al 2O 3 by HREM with atomic resolution

Abstract

High resolution electron microscopy and image calculations are performed on MoS 2 γ- Al 2O 3 based catalysts. It is shown that HREM allows atomic imaging of the MoS 2 particles on the alumina carrier. Restrictions with respect to atomic imaging are found from image simulations. The orientation of the slabs with respect to the electron beam is important. Whereas atomic imaging can be obtained in 〈100〉 and 〈110〉 directions, 〈001〉 oriented crystals will be invisible by HREM because of the way the slabs are mounted on the alumina support. The slabs are basal bounded. Since essentially single slabs are observed, it is suggested that a strong interaction exists between the slabs and the alumina support. EDX analysis shows that the MoS 2 particles are sulfur deficient. We suggest that sulfur deficiency is present in the first sulfur layer on the γ-Al 2O 3 support. In specimens sulfided below 673 K an intermediate phase is present, which is presumably an oxy-sulfide of molybdenum.