Insights into the essential roles of tin and chloride species within Cu–CeO2 based catalysts for CO preferential oxidation in H2-rich stream

Abstract

Sn modified Cu–Ce catalysts have been synthesized by the solvent-free combustion method for preferential oxidation of CO in H2-rich stream (CO-PROX) and characterized by N2 adsorption-desorption (BET), H2 temperature-programmed reduction (H2-TPR), X-ray diffraction (XRD), Raman, in-situ DRIFTS, X-ray photoelectron spectroscopy (XPS), and Oxygen storage capacity (OSC). The results show that the incorporation of Sn species accelerates the redox cycle among Sn, Cu and Ce, thus strengthening the Cu–Ce interaction and promoting the formation of surface and bulk lattice Cu-[Ox]-Ce structures Meanwhile, to balance the charge, more oxygen vacancies are formed and thus facilitate the migration of oxygen species. Combined with the more strong absorbed ability of SnO2 for O2, active Cu-[Ox]-Ce structures promotes the easier conversion of more CO into CO2. However, the existence of Cl ions decreases catalytic performance because the formation of CuCl makes the Cu–Ce interaction weakened, resulting in the formation of fewer Cu-[Ox]-Ce structures and oxygen vacancies. Although CuCl is prone to be in favor of absorbing more CO, there are not enough O species available, hence a decrease in performance is observed.