Abstract
One-pot deposition of Au onto TiO2 has been achieved through directly contacting gold (III) salt with nanosized functionalized TiO2 support initially obtained by sol-gel process using titanium isopropoxide and citric acid. Citrate groups act as functional moieties able to directly reduce the Au salt avoiding any further reducing treatment. Various gold salts (NaAuCl4 center dot 2H(2)O or HAuCl4 center dot 3H(2)O) and titanium to citrate (Ti/Cit) molar ratios (20, 50 and 100) were used in order to study the effect of the nature of the precursor and of the citrate content on the final Au particle size and catalytic properties of the as-obtained Au/TiO2 materials.
Au/(TiO2)(x)(Cit)(1) catalysts characterization was performed using N-2 adsorption-desorption, ICP-AES, X-ray diffraction and TEM. The effect of the Ti/Cit molar ratio and of the gold precursor was evaluated. The selective oxidation of benzyl alcohol (BzOH) to benzaldehyde (BzH) was studied as a model reaction. Kinetic analysis showed that the catalytic reaction rate was pseudo first-order and the values of activation energy have been reported. Results showed that the functionalization of TiO2 by citrate allows tuning the size of the Au nanoparticles deposited onto TiO2 as well as their morphology. Citrate also strongly enhances the benzyl alcohol oxidation through the control of the size and morphology of gold nanoparticles. (C) 2014 Elsevier B.V. All rights reserved.