Water–gas shift catalysis over transition metals supported on molybdenum carbide

Abstract We report here that WGS rates per total surface area at 120 °C, 7% CO, 22% H 2 O, 8.5% CO 2 , 37% H 2 for Pt, Au, Pd and Ni supported over Mo 2 C were 4–8 times higher than those of the commercial Cu/ZnO/Al 2 O 3 catalyst. In agreement with previous literature, the WGS rate per total moles of Pt over Pt/Mo 2 C at 120 °C has been shown to be higher than on any Pt/Metal oxide catalyst. We have made use of systematic changes in the apparent kinetic parameters with various admetals (decrease in apparent CO order and apparent activation energy and increase in apparent H 2 O order compared to unpromoted Mo 2 C) to conclude that the function of the rate-promoting admetals is to enhance the relative surface concentration of the adsorbed CO, thereby leading to a promotion in the WGS rate per total surface area of the catalyst. Temperature programmed desorption of CO was used to show that the CO adsorption properties of Mo 2 C were modified by the various admetals by creating new metallic sites. In situ X-ray absorption on Pt and Au and STEM–EELS experiments showed that the supported Au nanoparticles over Mo 2 C decrease in average particle size from ∼9 nm to 3 nm after a 600 °C carburization pretreatment. Pt was also shown to have assumed a stable structure at 600 °C in the form of a Pt–Mo alloy. We suggest that Mo 2 C can be used to synthesize thermally robust supported metal catalysts.