Decoration of Gold and Platinum Nanoparticle Catalysts by 1 nm Thick Metal Oxide Overlayer and Its Effect on the CO Oxidation Activity.

Exfoliated M-Al layered double hydroxide (M-Al LDH; M = Mg, Co, Ni, and Zn) nanosheets were adsorbed on Au/SiO and calcined to transform LDH into mixed metal oxides (MMOs) and yield Au/SiO coated with a thin MMO overlayer. These catalysts showed a higher catalytic activity than pristine Au/SiO. In particular, the 50% CO conversion temperature decreased by more than 250 °C for Co-Al MMO-coated Au/SiO. In contrast, the deposition of CoAlO on Au/SiO by impregnation or the deposition of Au on Co-Al MMO-coated SiO resulted in a worse catalytic activity. Moreover, the presence of a thick MMO overlayer decreased the catalytic activity, suggesting that the control of the overlayer thickness to less than 1 nm is a requisite for obtaining a high catalytic activity. Moreover, the thin Co-Al MMO overlayer on Au/SiO possessed abundant oxygen vacancies, which would play an important role in O activation, resulting in a highly active interface between Au and the defect-rich MMO on the Au NP surface. Finally, this can be applied to Pt/SiO, and the obtained Co-Al MMO-coated Pt/SiO also exhibited a much improved catalytic activity for CO oxidation.