Atomic-Scale Structure of the Cobalt-Promoted Catalyst

Atomic-Scale Structure of the Cobalt-Promoted Catalyst 

By applying an approach similar to the one taken with the unpromoted M0S2 nanoclusters, we recently managed to synthesize a model system for the promoted CoMoS catalyst 119). As a result of co-deposition of molybdenum and cobalt onto the Au(l 1 1) crystal during exposure to an H2S atmosphere and subsequent annealing, crystalline CoMoS clusters formed on the Au(l 1 1) terraces. As shown in Fig. 24, the main new finding is that the CoMoS nanoclusters now adopt a 

On the basis of the detailed atomic-scale information provided by the STM images, a structural model of the CoMoS nanoclusters is proposed in which cobalt atoms have replaced molybdenum atoms along the sulfur edges of hexagonally truncated nanoclusters. As depicted in the ball model in Fig. 25(a) and (c), a tetrahedral environment of the cobalt atoms is produced if the outermost protrusions are assumed to be sulfur monomers, which agrees well with spectroscopic results reported for supported CoMoS catalysts (93,137-139 and previous DFT investigations (128,140.  

Ft = -95.2mV and/j = 0.81 tiA. Note the intense brim associated with the cobalt-substituted sulfur edge 

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D.S. Atomic-Scale Structure of the Cobalt-Promoted Catalyst... 

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