Alumina supported Pt–Mo2C catalysts for the water–gas shift reaction

This paper describes the synthesis and characterization of catalysts with Pt deposited onto Mo2C supported on Al2O3 (Pt–Mo2C/Al2O3) and their evaluation for the water–gas shift reaction. Previously, we reported that Pt deposited onto Mo2C (Pt/Mo2C) was highly active for this reaction. Enhanced utilizations of the metal and carbide were expected for the Pt–Mo2C/Al2O3 catalysts. The materials were prepared using a wet impregnation method and characterized using techniques including X-ray diffraction, X-ray absorption spectroscopy, temperature-programmed desorption, and transmission electron microscopy. The presence of Mo2C enhanced the deposition of Pt from H2PtCl6 solutions. The Pt–Mo2C/Al2O3 catalysts were much more active than the corresponding Pt/Al2O3 catalysts. For example, the turnover frequency for the 3.8 wt.% Pt–Mo2C/Al2O3 catalyst at 240 °C (0.81 s−1) was two orders of magnitude higher than that for the 3.9 wt.% Pt/Al2O3 catalyst (0.007 s−1). Trends with increasing Pt loading for the Pt–Mo2C/Al2O3 catalysts were similar to those previously observed for Pt/Mo2C catalysts. The results are consistent with Pt being co-located with Mo2C, a consequence of the strong affinity of the Pt precursor for Mo2C. Interaction of the Pt with Mo2C would account for the significant differences between the catalytic and the surface chemical properties of the Pt–Mo2C/Al2O3 and Pt/Al2O3 catalysts.