Modulating Nanoparticle Structure by Metal-Metal Oxide Interfacial Interaction in a CeO-Supported Bimetallic System: The Ni-Cu Case.

Structure-optimized bimetallic and multicomponent catalysts often outperform single-component catalysts, inspiring a detailed investigation of metal-metal and metal-support interactions in the system. We investigated the geometric and electronic structures of ceria-supported Ni-Cu particles prepared using different metal deposition sequences employing a combination of X-ray photoelectron spectroscopy, resonant photoemission spectroscopy, and infrared reflection absorption spectroscopy. The bimetallic model catalyst structure was altered by a distinct surface evolution process determined by the metal deposition sequence. The postdeposited Cu stays on the surface of Ni predeposited CeO and forms only a limited Ni-Cu alloy in the Cu-contacted Ni region. However, when Ni is deposited on the Cu predeposited CeO surface, Ni can migrate through the Cu layer to the Cu-ceria interface and form an extended Ni-Cu alloy to the whole deposited metal layer on the ceria surface. The dynamic metal diffusion in the CeO-supported Ni-Cu system indicates that metal-support interactions can be used to achieve the rational design of a bimetallic composition distribution during catalyst preparation.