Understanding water-gas shift reaction mechanisms at palladium–ceria interfaces using in situ SERS coupled with online mass spectrometry

Abstract

Understanding water activation and reaction at metal-oxide interfaces is of significant importance. However, it remains a great challenge due to the weak signal of surface-active species and the difficulties associated with in situ detection methods. Herein, the water-gas shift reaction mechanism at the Pd–CeO₂ interfaces has been systematically studied by using the “borrowing” surface-enhanced Raman spectroscopy (SERS) strategy through the fabrication of Au@CeO₂–Pd core–shell satellite structures. Through the combination of in situ SERS and online mass spectrometry, real-time monitoring of surface intermediate species and reaction products is achieved simultaneously. It is found that CO adsorbed on Pd can either react with the oxygen species formed via water dissociation (the associative mechanism) or the lattice oxygen in CeO₂ (the redox mechanism), with the former having a higher activity. This work provides an effective approach for the in situ study of interfacial catalysis and explains the important role of the Pd–CeO₂ interfaces in the water-gas shift reaction at a molecular level.