Probing the active sites for water–gas shift over Pt/molybdenum carbide using multi-walled carbon nanotubes

[Display omitted] •Pt/Mo2C/MWCNT has WGS kinetic parameters similar to those of Pt/Mo2C at 120°C.•Structure of the catalyst is Pt–Mo nanoparticles preferentially bound to Mo2C.•WGS rate per gram at 120°C increases with the fraction of the support surface covered by Pt–Mo nanoparticles.•Pt–Mo nanoparticles perform CO activation, while Mo2C performs H2O dissociation. Pt/Mo2C is known to have water–gas shift (WGS) rate per total mole of Pt that is higher than on any oxide-supported Pt catalyst. The difficulties for the characterization of Pt/Mo2C were overcome by preparing the carbide using Multi-Walled Carbon Nanotubes (MWCNT), which showed the expected kinetics. X-ray absorption spectroscopy confirmed formation of alloy with Mo and STEM–EELS data confirmed the elemental composition of Pt particles as Pt–Mo for a series of Pt/Mo2C/MWCNT catalysts. A linear correlation is obtained between the WGS rate per gram at 120°C and the area covered by Pt–Mo alloy nanoparticles on Mo2C, estimated using STEM images. Pt is shown to preferentially bind to the Mo2C domains. The kinetic data in tandem with the characterization techniques suggest that the active sites are formed by Pt–Mo alloy nanoparticles in contact with Mo2C, not by the formation of the alloy. The water activation on Mo2C is suggested to be the cause for the higher WGS rate over Pt/Mo2C.