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

Revealing and 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 difficulty of 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), while the former has a higher activity. This work provides an effective way 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.