Structure and reactivity of Au–Rh bimetallic clusters on titanate nanowires, nanotubes and TiO 2(1 1 0)

Abstract

Au and Rh clusters, as well as Au–Rh bimetallic nanoparticles were prepared on titanate nanowires, nanotubes and on TiO 2(1 1 0). They were characterized by X-ray photoelectron spectroscopy (XPS), low energy ion scattering spectroscopy (LEIS) and Fourier transform infrared spectroscopy (FTIR). By performing careful LEIS experiments, it was found that for appropriate Au and Rh coverage, a thin Au layer almost completely covers the Rh nanoparticles, a Rh core–Au shell structure was detected. The formation of this structure was not affected by alkali (K) adatoms. LEIS and FTIR measurements disclosed that adsorbed CO at 300 K causes the segregation of Rh atoms to the surface of metal clusters in order to bind to CO. Upon CO adsorption on Rh/titanate nanostructures the IR stretching frequencies characteristic of the twin form were dominant, whereas bimetallic nanosystems featured a pronounced linear stretching vibration as well. In spite of this structure adsorbed CO is detectable during the ethanol adsorption on gold–rhodium bimetallic cluster and the ethanol decomposition rate is twice higher than on Au/TiO 2.