Understanding the morphology of catalytically active materials has been approached successfully in past decades using field electron microscopy in scanning and transmission modes. In this respect, some simulated TEM measurements for unsupported promoted molybdenum di-sulfide (MoS2/Co) provided some insights about molecular structure in those catalytic layered transition metal sulfides (LTMS). However, due to poor resolution, lack of color enhancement, and other factors, sections of those materials observed under TEM do not resolve the structure by itself; in particular about the localization of cobalt atoms for promoted MoS2 unsupported catalyst. This work concludes an epitaxial growth of MoS2 slabs over (111)-Co9S8 crystallographic plane, with a stacking degree size of 6 slabs. Results presented in here are obtained using experimental HRTEM and TEM simulations using the multi-slice method with a slice thickness of 25 Å and projected potential, where ai and bi are coefficients to be determined.

Locating cobalt promoters on catalytically MoS2 structures is a challenging task to achieve; this is due to the size on those MoS2 nanostructures. Previous reports in the literature indicate that specific locations for Co in MoS2 slabs are (1010)-plane creating either a sulfur-Co or Molybdenum-Co termination edge, due to lower energy required for the permutation Mo, S and Co to occur. We present results obtained from Density Functional Theory study done on the interface between MoS2 and Co9S8 crystal structures; the interface show an interesting thiocubane cluster and it is suspected to be the responsible for Mo-S-Co bonding to exist, along with HDS reaction. In order to understand electronic properties on thiocubane Density of States and Mulliken Population Analysis calculations were implemented using Cambridge Serial Total Energy Package (CASTEP). Results indicate a strong electron donation from Co to Mo through intermediate sulfur atom bonded to both metals while an enhanced metallic character is also found.

In the last decades, HRTEM approach has been quite fruitful to study structural characteristics of layered transition metal sulfide (LTMS) catalytic materials since providing direct local information about the structural organization of this quite important class of catalysts at the nanoscale level. However, up to now, HRTEM observations of some common localized structural organization like honeycomb-like structures have remained unexplained. In the present study, a structural model corresponding to stacked 2H-MoS2 slabs twisted along their basal direction is proposed to explain honeycomb like-structures observed by HRTEM. This model is based on a comparison between experimental and simulated images of 2H-MoS2 catalysts promoted with cobalt. The resulting Density of States (DOS) of the twisted structure was then calculated.

Synthesis of Au, Ag monometallic, and Au-Ag bimetallic nanoparticles have been synthesized by successive reduction of metal salts with ascorbic acid on prefabricated seeds in the presence of cetyltrimethylammonium bromide (C16H33)N(CH3)3Br (CTAB), as a cationic surfactant, is presented in this paper. This coverage method for the prefabricated seeds is uniform, although in some cases deviations from a spherical shape are observed with the formation of nanorods or nanoprisms. Results using high-resolution STEM-XEDS elemental mapping suggest that the actual distribution of the two metals within the multilayer spheres may involve partial alloying of the metals.

Polycrystalline metal borides AlMgB14, CaB6, and MB2 (M: transition metals) were synthesized and their thermoelectric properties were examined. Single phase of orthorhombic AlMgB14, which contains B12 icosahedral clusters as building blocks, was obtained at sintering temperatures between 1573 K and 1823 K. Seebeck coefficient (α) and electrical conductivity (σ) of the phase were about 500 (μV/K) and 10−1 (1/Ωm) at room temperature, respectively. These values are comparable to those of metal-doped β- rhombohedral boron. Synthesized AlB2-type diborides (MB2; M=Ti, V, Cr, and Mn) exhibited metallic conduction. The MB2's α varied with number of valence electrons, and showed a maximum α in VB2. The variation was similar to that predicted for pseudogap system. The CaB6 also possessed metallic conduction, but the α of the phase was as large as 200 (μV/K) with negative sign.