(222f) Platinum Supported on Molybdenum Carbide for the Water-Gas Shift Reaction, a Theoretical and Experimental Study

Early transition metal carbides have been demonstrated to be highly active in a variety of important catalytic reactions including hydrogenation, desulfurization, water-gas shift, and steam reforming. These high surface area materials could also serve as supports both for thermochemical catalysts as well as electrocatalysts given their high electronic conductivities. We recently developed a method to support metals onto high surface area early transition metal carbides. The resulting catalysts possess exceptional activities and selectivities. In this paper, we present results for the water-gas shift reaction. The particular focus of our efforts has been molybdenum carbide supported platinum catalysts. Activities for these catalysts were much higher than those for either SiO2 support Pt (modeling metallic platinum) or molybdenum carbide alone. X-ray diffraction analysis indicated that the Pt domains were x-ray amorphous and highly dispersed on the carbide surface. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and a cyclic voltammetry technique have been used to characterize Pt on the surface. Using a well defined model based on the characterization of the surface, density functional theory was used to further elucidate the mechanism of the reaction on the surface. Platinum supported on molybdenum oxide was also tested and characterized. Comparing these results lead to a better understanding of how transition metal carbides used as catalyst supports can greatly enhance or diminish the activity of metal catalysts.