Consisted of closely packed nanoflakes, γ-Al 2 O 3 hollow microspheres with ca. 4-6 μm in diameter, and 500-700 nm in shell thickness have been hydrothermally synthesized through utilizing Al(NO 3) 3 •9H 2 O as precursor, urea as precipitant agent and sulfate K 2 SO 4 , (NH 4) 2 SO 4 , or KAl(SO 4) 2 •12H 2 O as additive, followed by a calcination step. The samples were further characterized by thermogravimetric analysis, scanning electron microscope, x-ray powder diffraction, nitrogen adsorption, and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) of adsorbed CO etc. The morphology of alumina products was strongly dependent on the presence of SO 4 2−. Then via a deposition-precipitation method, 3 wt.% Au nanoparticles supported on γ-Al 2 O 3 hollow microspheres exhibit excellent performance with a complete CO conversion at 0°C (T 100% =0°C) and 50 % conversion at −25°C (T 50% =−25°C). The good catalytic activity is associated with the special hollow microsphere structures assembled by nanoflakes of γ-Al 2 O 3 support. The DRIFTS confirms the presence of Au δ+ and Au 0 on the surface of γ-Al 2 O 3 hollow microspheres. As a contrast, Au catalyst prepared using alumina support with undefined morphology shows low activity under the same catalytic test conditions (T 100 % = 190°C, T 50 % =80°C). Keywords Hollow microspheres. γ-Al 2 O 3. Au catalyst. CO oxidation
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