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

• 16.2 wt.% Pt–Ir with atomic ratio of Pt/Ir 0.8 was impregnated on TiO2 nanotubes.
• The bimetallic clusters, with an average size of 0.9 nm, were very well dispersed.
• The bimetallic clusters were anchored on surface O vacancy sites.
• The clusters could have malleable polyhedral morphologies with low-energy facets.
• The cluster had big amount of surface atoms and low coordination number.

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.

This manuscript reports the synthesis and characterization of Pt–Ir/TiO2 nanotube catalysts with a high metallic load of platinum and iridium. The metals were highly dispersed on the nanotubular surface of titanium oxide as bimetallic nanoparticles. The average size was around 0.9 nm.Figure optionsDownload as PowerPoint slide