Simultaneous sulfidation of Mo and Co oxides supported on Au(111).

Here we present the results of a study carried out to investigate the simultaneous sulfidation of Co and Mo oxide nanoparticles on Au(111) as a synthesis strategy to prepare a model catalyst for hydrodesulfurization (HDS). We make use of scanning tunneling microscopy and X-ray photoelectron spectroscopy to track the changes in morphology and chemistry during the synthesis of a mixed Mo and Co oxide precursor and the sulfidation thereafter, to the respective sulfides. We investigated the effects of temperature and the duration of sulfidation on the completeness of the sulfidation process. Our study shows that the formation of MoS with the CoMoS edge (the desired model catalyst) is not affected by the time or the temperature of sulfidation. However, the yield of the Co-promoted MoS slabs is limited by the formation of large clusters due to the spreading of Mo and Co oxide phases upon sulfidation. Complete sulfidation of the mixed oxide precursor to Co-promoted MoS can be accelerated by increasing the sulfidation temperature to 730 K due to the thermally activated nature of Mo oxide sulfidation. Thus, we demonstrate that using a mixed Mo and Co oxide precursor as a starting point for the Co-promoted MoS phase for fundamental catalytic studies is a viable strategy.