Study of catalysts based on Au-M (Ir, Pd, Pt and Ru) loaded onto TiO2 for enhanced carbon monoxide oxidation at low temperatures

• Au, Ir Pt, Pd, and Ru mono and bimetallic catalysts were tested for CO oxidation reaction. • Au-Pd and Au-Ir bimetallic catalysts enhanced the CO oxidation reaction. • Monometallic Ru and Pd catalysts showed activity for the CO oxidation reaction at 25 °C. • Different ratios of Au 0 /Au + species are generated in Au-M (Ir, Pd, Pt, and Ru) systems. Supported mono and bimetallic Au catalysts have evidenced to be overly effective catalyzing the CO oxidation at low temperature. The bimetallic Au-Pd and Au-Ir catalysts with small amounts of Au, Pd or Ir (1 wt%) displayed homogeneously distributed particles (average metal particle size between 1 and 2 nm), and strong metal–metal interactions, which exerted a fundamental effect on the CO oxidation at low temperature. These bimetallic nanostructures afforded a stable CO oxidation at low temperatures (from −5 °C to 25 °C). DRIFTS analyses revealed different interactions between CO and the metals, suggesting a different degree of interaction between Au and Ir, Pd, Pt or Ru. Through DFT calculations, it was found that Pd induced high fluxionality on the supported bimetallic catalysts and that Ir produced greater distortion over the TiO 2 surface upon adsorption; then, both effects could have been contributing to the high catalytic activity displayed by these materials.