Abstract
This paper remarks the general correlations of the shape and crystallinity of titanium dioxide (TiO2) support on gold deposition and carbon monoxide (CO) oxidation. It was found that due to the larger rutile TiO2 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 TiO2 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 TiO2 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 Au0 content (68 mg/g catalyst). CO oxidation activity was also found to be directly proportional to the Au0 content. Based on diffuse reflectance infrared Fourier transform spectroscopy, we postulate that anatase TiO2-supported Au undergoes rapid direct oxidation whilst CO oxidation on rutile TiO2-supported Au could be inhibited by co-adsorption of oxygen.
Highlights
The first publication on the oxidation of carbon monoxide (CO) using gold (Au) as catalyst was published by Bone and Andrew [1] in 1925
This study aims to provide a general correlation relating CO oxidation activity with Au particle size, Au loading, and Au3+ /Au0 content, for Au-TiO2 synthesized using sol–gel and light emitting diode (LED)
The sizes of the as-prepared rutile TiO2 were in the range of 40–60 nm, about twice the sizes of anatase TiO2, due to the transformation of two or more of the anatase TiO2 particles under higher calcination temperature which favors particle growth
Summary
The first publication on the oxidation of carbon monoxide (CO) using gold (Au) as catalyst was published by Bone and Andrew [1] in 1925. In the 1970s, Bone and Sermon [2] deposited gold on different supports—magnesium oxide, aluminum oxide and silicon oxide using thermal decomposition method, and demonstrated the hydrogenation of olefins at 100 ◦ C. A large number of studies were carried out to improve the catalytic activity of Au nano-particles; the dominant factors can be divided into four categories [14]: type and morphology of support [15,16,17], the Au particle size [18], the nature of the active sites [19,20], and the preparation method including the pre-treatment [21]. It was found that when the Au particle gets smaller, the number of edge or kink
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