Direct identification of the carbonate intermediate during water-gas shift reaction at Pt-NiO interfaces using surface-enhanced Raman spectroscopy

Abstract

Noble metal-reducible oxide interfaces have been regarded as one of the most active sites for water-gas shift reaction. However, the molecular reaction mechanism of water-gas shift reaction at these interfaces still remains unclear. Herein, water-gas shift reaction at Pt-NiO interfaces has been in-situ explored using surface-enhanced Raman spectroscopy by construction of Au@Pt@NiO nanostructures. Direct Raman spectroscopic evidence demonstrates that water-gas shift reaction at Pt-NiO interfaces proceeds via an associative mechanism with the carbonate species as a key intermediate. The carbonate species is generated through the reaction of adsorbed CO with gaseous water, and its decomposition is a slow step in water-gas shift reaction. Moreover, the Pt-NiO interfaces would promote the formation of this carbonate intermediate, thus leading to a higher activity compared with pure Pt. This spectral information deepens the fundamental understanding of the reaction mechanism of water-gas shift reaction, which would promote the design of more efficient catalysts. Direct spectroscopic evidence of the carbonate intermediate and its evolution during water-gas shift reaction at Pt-NiO interfaces is obtained using surface-enhanced Raman spectroscopy, based on which the reaction mechanism is then proposed.