Insight into the Role of Isolated Gold Atoms-Ceria Conjunction in Catalyzing the Water-Gas Shift Reaction

As the promising catalysts for the water-gas shift (WGS) reaction, the activity of Au-CeO2 composites is susceptible to the aggregation size and electronic state of Au species. Previous reports were extensively focused on the discrepancy between nonmetallic Au and metallic Au nanoparticles, whereas the understanding of the authentic role of the isolated Au atoms was limited. Herein, we investigated the catalytic behavior and structural information over two types of Au/CeO2 catalysts, in which the predominant conjunctions were isolated Au-1-CeO2 and Au-n-CeO2, respectively. Based on comprehensive characterizations, particularly by in-situ Raman and in-situ DRIFTS, we found that the isolated Au atoms were responsible for enhancing the reducibility of the CeO2 matrix. The CO adsorption ability on the isolated Au sites was significantly inferior to clustered Au atoms, especially at relatively high temperatures (> 200 degrees C). As a result, the boosted O vacancy on the isolated Au-1-CeO2 conjunctions could improve the H2O activation ability for the Au-CeO2 catalysts and demonstrate a comparable activity to the clustered Au-n-CeO2 sites. This work might deepen understanding of the catalytic function for the isolated Au-1 site within Au/CeO2 systems while catalyzing the WGS reaction.