CO Oxidation on Au/α-Fe₂O₃-Hollow Catalysts: General Synthesis and Structural Dependence

Gold nanoparticles supported on iron oxides are highly active catalysts for the CO oxidation even at low temperatures, and their activity strongly depends on the nature of the Fe 2 O 3 support. In the present work, we found a facile route to synthesize α-Fe 2 O 3 nanoparticles with a hollow architecture via a hydrothermal–thermal decomposition process without utilization of templates and surfactants. The key of this synthetic strategy is to induce the formation of hole-like surface defects on the β-FeOOH nanorod precursors with relatively small diameters (20–30 nm) and give a suitable temperature gradient to enhance the volume diffusion of such defects during heating. Finally, the hollow structure can be evolved from the growth of the surface defect clusters on the nanorods. For comparison, α-Fe 2 O 3 nanoparticles with other typical morphologies (i.e., spindle, rod, and hollow rod) were also prepared. Au nanoparticles (2–5 nm) were well dispersed on the different α-Fe 2 O 3 supports via a colloid-deposition method. The prepared Au/α-Fe 2 O 3 -hollow catalyst exhibits superior catalytic performance for CO oxidation compared to the others. This can be attributed to the relatively high exposure degree of surface defects in the unique hollow structure, which could strongly improve the gold–support interaction. The investigations with the aid of X-ray photoelectron spectroscopy and in situ diffuse reflectance infrared Fourier transformation spectroscopy suggested that the intimate gold–support interaction brings about more active surface species (i.e., – OH groups and adsorbed oxygen) for CO oxidation.