Catalytic oxidation of carbon monoxide at low temperature using AuRh/TiO2 bimetallic catalysts: Effect of the synthesis method

AuRh nanoparticles supported on TiO2 P25 were synthesized by two sequential deposition methods: sequential deposition-precipitation with urea (DPU) and impregnation (IMP)-DPU. Segregated nanoparticles (RhcoreAushell ball-cup-type, and Janus-type arrangements) were observed in gold-rhodium bimetallic catalysts, but mainly ball-cup-type and Janus-type nanoparticles were found on catalysts prepared by IMP-DPU. XPS analysis of gold-rhodium bimetallic catalysts, before and after reaction allowed concluding that gold-rhodium interaction on metallic state was an important factor to avoid the oxidation of rhodium during CO oxidation. However, this effect of stabilization of the rhodium metallic phase by gold does not fully explain the promoting effect observed for some bimetallic catalysts on CO oxidation. Some structural aspects such as the atomic arrangement of the bimetallic nanoparticles and the type of active sites, determined by DRIFTS-CO, were also considered. TPR and UV–visible DR spectroscopy characterizations also showed differences in the gold-rhodium interactions.