Influence of the CeO₂ Support on the Reduction Properties of Cu/CeO₂ and Ni/CeO₂ Nanoparticles

Abstract

Ceria (CeO₂) is being increasingly used as support of metallic nanoparticles in catalysis due to its unique redox properties. Shedding light into the nature of the strong metal support interaction (SMSI) effect in CeO₂-containing catalysts is important since it has a strong influence on the catalytic properties of the system. In this work, Cu/CeO₂ and Ni/CeO₂ nanoparticles are characterized when submitted to a reduction treatment at 500 °C in H₂ atmosphere with a combination of in situ (XAS – X-ray absorption spectroscopy and time-resolved XAS) and ex situ (TEM – transmission electron microscopy and XPS - X-ray photoelectron spectroscopy) techniques. The existence of a capping layer decorating the Ni/CeO₂ nanoparticles after the reduction treatment is shown, representing evidence for the SMSI effect. The kinetics of the SMSI occurrence is elucidated. It is proposed that the electronic factor of the SMSI effect has a strong influence on the reduction properties of the Ni nanoparticles supported on CeO₂, decreasing its reduction temperature if compared to nonsupported Ni nanoparticles. The same phenomenon is not observed for Cu/CeO₂ nanoparticles, where there is no evidence for the SMSI effect, and no changes on the reduction properties between supported and nonsupported Cu nanoparticles are observed