Abstract
This paper remarks the general correlations of the shape and crystallinity of titanium dioxide (TiO&sub2;) support on gold deposition and carbon monoxide (CO) oxidation. It was found that due to the larger rutile TiO&sub2; particles and thus the pore volume, the deposited gold particles tended to agglomerate, resulting in smaller catalyst surface area and limited gold loading, whilst anatase TiO&sub2; enabled better gold deposition. Those properties directly related to gold particle size and thus the number of low coordinated atoms play dominant roles in enhancing CO oxidation activity. Gold deposited on anatase spheroidal TiO&sub2; at photo-deposition wavelength of 410 nm for 5 min resulted in the highest CO oxidation activity of 0.0617 mmol CO/s.gAu (89.5% conversion) due to the comparatively highest catalyst surface area (114.4 m²/g), smallest gold particle size (2.8 nm), highest gold loading (7.2%), and highest Au&sup0; content (68 mg/g catalyst). CO oxidation activity was also found to be directly proportional to the Au&sup0; content. Based on diffuse reflectance infrared Fourier transform spectroscopy, we postulate that anatase TiO&sub2;-supported Au undergoes rapid direct oxidation whilst CO oxidation on rutile TiO&sub2;-supported Au could be inhibited by co-adsorption of oxygen.