Enhanced CO catalytic oxidation over an Au–Pt alloy supported on TiO2 nanotubes: investigation of the hydroxyl and Au/Pt ratio influences

Incorporating another transition metal into gold-based catalysts has been shown to be beneficial to their catalytic performance. To better understand the origin of this catalytic behavior, Au–Pt alloy catalysts supported on thermally stable TiO2 nanotubes (TiO2 SNTs) were prepared, and their structural properties, adsorption of CO, and catalytic activity for CO oxidation were investigated. The alloy structure was confirmed by STEM and UV-vis spectroscopy, and the Au–Pt alloy phase could enhance the metal–support interaction (MSI). The catalytic results and DFT analysis indicated that the Au–Pt/TiO2 SNTs calcined at 400 °C with an Au/Pt ratio = 5 : 1 had the best CO catalytic performance. Based on the XPS and DRIFT results, the synergetic effects between Au and Pt and the hydroxyl groups of the Au–Pt/TiO2 SNT catalysts played a vital role in the catalytic activity. The hydroxyls bonded onto the cationic Au can react with CO molecules adsorbed on the surface of Au or Pt NPs to form intermediates COOH. The accompanying density functional theory (DFT) calculation results also reveal the determining role of OH in Au–Pt/TiO2 SNT catalysts. A possible catalytic mechanism of the Au–Pt/TiO2 SNT catalysts with enhanced catalytic activity was also proposed.