Robust Gold-Decorated Silica−Titania Pebbles for Low-Temperature CO Catalytic Oxidation

A deposition−precipitation (DP) process was used to prepare silica−titania core−shell pebbles decorated with nanocrystalline gold suitable for low-temperature catalytic oxidation of carbon monoxide (CO). The microstructure, phase content, crystallography, and catalytic activity were correlated with the pH (3−8), aging time (15, 30, 60 min), and heat treatment employed for gold crystallization (200−400 °C). A homogeneous metal distribution, high gold loading (3.7−4.4 wt %), and superior interfacial adhesion between gold and titania were obtained when the support pebbles were prepared at 600 °C, a temperature lower than that required for the anatase-to-rutile transformation. Nucleation and growth of {111} faceted gold was favored at mid-pH (6.4−8), while smaller crystals (