Support morphology-dependent alloying behaviour and interfacial effects of bimetallic Ni–Cu/CeO2 catalysts

Abstract

The impregnation method is commonly employed to prepare supported multi-metallic catalysts but it is often difficult to achieve homogeneous and stable alloy structures. In this work, we revealed the dependence of alloying behavior on the support morphology by fabricating Ni–Cu over different shaped CeO₂. Specifically, nanocube ceria favoured the formation of monometallic Cu and Ni-rich phases whereas polycrystalline and nanorod ceria induced the formation of a mixture of Cu-rich alloys with monometallic Ni. Surprisingly, nanopolyhedron (NP) ceria led to the generation of homogeneous Ni–Cu nanoalloys owing to the equivalent interactions of Ni and Cu species with CeO₂ (111) facets which exposed relatively few coordinative unsaturated sites. More importantly, a strong interfacial effect was observed for Ni–Cu/CeO₂-NP due to the presence of CeO_x adjacent to metal sites at the interface, resulting in excellent stability of the alloy structure. With the aid of CeO_x, NiCu nanoalloys showed outstanding catalytic behaviour in acetylene and hexyne hydrogenation reactions. This study provides valuable insights into how fully alloyed and stable catalysts may be prepared by tailoring the support morphology while still employing a universal impregnation method.