Structural characterization of Pt-Ir bimetallic clusters on TiO₂ nanotubes prepared by simultaneous reduction

In this work we report the impregnation of 16. wt.% Pt and Ir on titania nanotubes. The metal load was fully dispersed on nanotubular support as Pt-Ir bimetallic particles of subnanometric size around 0.9. nm and polyhedral morphologies. Larger Pt or Ir phase segregation was not observed. The impregnation and dispersion of the metals were made through the co-impregnation method by chemical vapor deposition modified. The reduction of both metallic salts was carried out under inert atmosphere at 400. °C. The samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy using a relatively new technique as high angle annular dark field scanning transmission electron microscopy (STEM) with corrected-aberration and energy dispersive X-ray spectroscopy in the STEM mode. Concentrations of 8.94. wt.% Ir and 7.27. wt.% Pt in the sample were detected by SEM-EDX. Statistical analysis of the chemical composition performed on 50 single nanoparticles by STEM-EDX showed that all were bimetallic. The average chemical composition was around 56.6. wt.% Ir and 43.4. wt.% Pt. Nevertheless, the compositional distribution varied from 15 to 95. wt.% Ir.