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

• Sodium-promoted platinum catalysts were prepared on oxidized multi-walled carbon nanotubes by an ion exchange method.
• In the presence of sodium, the carbon-supported Pt catalysts are active for the water-gas shift reaction.
• The removal of surface oxygen groups prior to Pt addition increases the activity due to improved interactions of sodium with platinum.
• The Pt-Na-OHx active site is stable over prolonged time-on-stream under product-free water-gas shift reaction conditions.

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 °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.

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