An Investigation of the Nature of Active Sites On Pt/Mo2C Water-Gas Shift Catalysts

Early transition metal carbides are catalytically active for a variety of reactions, such as isomerization reactions, hydrogenation reactions, water-gas shift (WGS), and hydrocarbon steam reforming. Because of their high surface areas, these materials are also interesting catalyst supports. In this paper we compare the properties of Pt supported on molybdenum carbide, as well as more traditional oxide supports including TiO2, MoO2, and Al2O3. The Pt/Mo2C possessed especially high activities for WGS. Chemical and physical properties of the materials were characterized using pulse chemisorption experiments and density functional theory calculations.

Our results suggest that the WGS reaction occurs either at the interface of the Pt particles and the Mo2C support. We will demonstrate that the reaction follows a bifunctional, red-ox type, mechanism over the Pt/Mo2C catalyst. The molybdenum site facilitates the dissociation of water, binding the oxygen atom while releasing an H2 molecule. The platinum serves as an adsorption site for CO, which can then be oxidized by the bound oxygen and released as CO2. These and other results and conclusions will be described in this talk.