Activation of carbon-supported platinum catalysts by sodium for the low-temperature water-gas shift reaction

The activation of multi-walled carbon nanotube-supported platinum catalysts for the low-temperature water-gas shift reaction is demonstrated by the addition of sodium. Nitric acid oxidation of the carbon nanotubes allows for the addition of sodium through ion-exchange and creates anchoring sites for platinum. We show that an oxidized platinum state is stabilized by the presence of sodium. Evidence for a sodium-promoted Pt-(OH)(x) active site is given through XPS analysis of the catalysts before and after reaction and confirmed by CO-TPR. Removal of the oxygen groups and partial removal of sodium by annealing the Na-modified carbon nanotubes to 800 degrees C in inert atmosphere creates a surface on which Pt is initially very active, but of lower stability due to the absence of a sufficient number of surface sodium anchoring sites. (C) 2013 Elsevier B.V. All rights reserved.