Nature of active sites at Pt/CeO2 interfaces for the water-gas-shift reaction

Abstract

Abstract Understanding the atomistic structure of the active site during catalytic reactions is of paramount importance in both fundamental studies and practical applications, but such studies are challenging due to the complexity of heterogeneous systems. Using Pt/CeO2 as an example, we reveal the dynamic nature of active sites during the water-gas-shift reaction (WGSR) by combining multiple in situ characterization tools to study well-defined CeO2 nanoshapes with different exposed facets. We show that metallic Pt is present on the CeO2(111) surfaces, while oxidized Pt species are dominant on CeO2(110) and (100) surfaces after O2–H2 pretreatment. The different concentrations of interfacial Ptδ+ – O – Ce4+ moieties at Pt/CeO2 interfaces are responsible for the rank of catalytic performance of Pt/CeO2 catalysts: Pt/CeO2-rod > Pt/CeO2-cube > Pt/CeO2-oct. For all the catalysts, metallic Pt is formed during the WGSR, leading to the transformation of the active sites to Pt0 – Ov – Ce3+ and interface reconstruction. These findings shed light on the nature of the active site for the WGSR on Pt/CeO2 and highlight the importance of combining complementary in situ techniques for establishing structure-performance relationships.