The effect of Au domain size on the CO oxidation catalytic activity of colloidal Au–FeOx dumbbell-like heterodimers

•Au@FeOx dumbbell nanocrystals with 4, 6 and 10 nm Au domain successfully synthesized.•Enhanced activity in CO oxidation, good sintering resistance and good stability.•Dumbbells with 4 nm Au domains were found to be the most active ones.•Iron oxide coating of Au NCs responsible for the limited TOF in 4 nm Au@FeOx dumbbells.

Au@FeOx dumbbell nanocrystals (NCs) with different sizes of the Au domain (i.e. 4 nm, 6 nm and 10 nm) were successfully synthesized by means of a colloidal synthesis procedure. They were then deposited on γ-alumina and tested in CO oxidation. The use of alumina minimized the contribution of the Au-support interaction in the CO oxidation, thus enabling us to clearly identify a synergy between the Au and the iron oxide that eventually resulted in an enhanced activity in CO oxidation, good sintering resistance and good stability of the catalytic performances. Among the three gold sizes tested, the dumbbells with 4 nm Au domains were found to be the most active ones. Nevertheless, we found that the activity of the 4 nm dumbbells was significantly hampered by the limited exposure of the Au or of the Au/iron oxide interface to the reacting environment.

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