Role of the nature of support on the structure of Au-Rh bimetallic nanoparticles

Au, Rh, and Au-Rh clusters were studied on Al2O3, TiO2 powders and titania nanowire by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and infrared spectroscopy (FTIR). On the XP spectra of the Au-Rh/TiO2 and Au-Rh/Al2O3 powders and wires the binding energy of the Au 4f emission was practically unaffected by the presence of Rh, the position of Rh 3d remained also constant on alumina, while it shifted to lower binding energy with gold admixture on titania. New emission for Rh 3d at 309.2 eV and for Au 4f at 85.6 eV developed on titania wire case. The bands due to Rho-CO and (Rho)(2)-CO were observed on IR spectra of titania supported bimetallic samples. The peak due to Rh+-(CO)(2) was less intense on bimetallic nanowire. All three bands however are intense on Au-Rh/Al2O3. The results were interpreted by electron donation from titania through gold to rhodium. "Core-shell" bimetallic structures are supposed on Au-Rh/titania wire. (C) 2011 Elsevier Ltd. All rights reserved.