Au-Ru/TiO2 prepared by deposition-precipitation with urea: Relevant synthesis parameters to obtain bimetallic particles

Although Au and Ru are not miscible in the bulk, the paper focusses on the attempts to prepare bimetallic Au-Ru/TiO2 catalysts by deposition-precipitation with urea (co-DPU and sequential DPU, Au then Ru and vice versa). Gold was found already reduced after the preparations of co-DPU and Ru then Au DPU, leading to large gold particles and to catalysts as poorly active as Ru/TiO2 in CO oxidation. The Au-Ru/TiO2 catalysts prepared by Au then Ru DPU provided the most interesting results: small bimetallic particles were formed; after reduction in H-2 at 300 degrees C, their structure was Janus-type and Au core - Ru shell, and the catalyst was poorly active, whereas after reduction at 500 degrees C, the particles became mainly Ru core - Au shell, and the catalyst showed higher activity than Au/TiO2 and a synergetic effect in CO oxidation compared to the monometallic counterparts.