Structural Studies of Copper Species in Supported CuO/CeO2 Catalyst by X-ray Absorption Spectroscopy Coupled with Pair Distribution Function Analysis

Abstract

Ceria-supported copper catalysts exhibit high catalytic performance in the preferential oxidation of CO in excess H₂ (CO PROX). Highly dispersed copper oxide species have been experimentally identified as active centers. However, structural diagnostics of highly dispersed CuO_x species and CuO_x/CeO₂ interface areas remains a challenge. Here, we report a comprehensive structural study of a supported CuO/CeO₂ catalyst (5 wt% Cu) showing good activity in the CO PROX process. X-ray absorption spectroscopy (XAS) techniques and X-ray atomic pair distribution function (PDF) analysis were used as efficient methods for probing the atomic resolution structure. It was established that the catalyst contains Cu²⁺ species, mainly in the form of ultra-dispersed CuO-like particles and copper oxide clusters. Analysis of the local atomic arrangement revealed an interaction between copper ions and ceria surface. Oxygen-terminated {100} ceria facets can accommodate Cu²⁺ ions in square planar coordination. Moreover, some Cu ions are inserted into the CeO₂ crystal structure, forming a substitutional solid solution.

Graphical Abstract