Atomic-scale structure of Co-Mo-S nanoclusters in hydrotreating catalysts

By means of scanning tunneling microscopy (STM), it has been possible to ob tain the first atomic-scale images of the Co-Mo-S structure present in hydr odesulfurization (HDS) catalysts. Information on the catalytically importan t edge structures has been obtained by synthesizing single-layer Co-Mo-S na noclusters using the Au(III) herringbone structure as a template, It is obs erved that the presence of the Co promoter atoms causes the shape of the Mo S2 nanoclusters to change from triangular to hexagonally truncated. This ch ange in morphology appears to be driven by a preference for Co to be locate d at the S-edge of MoS2. The results also directly show that the presence o f the Co atoms perturbs the local electronic environment of neighboring S a toms and this provides further insight into the effect of the promoter atom s. (C) 2000 Academic Press.