Abstract
Gold nanoparticles (Au NPs) were prepared by reducing HAuCl4 with NaBH4. Their average particle sizes could be tuned in the range of 1.7 and 8.2 nm, by adjusting the amount of NaBH4 used during synthesis. The obtained Au NPs (colloids) were then loaded onto a commercial Al2O3 support to prepare Au/Al2O3 catalysts with tunable Au particle sizes. An optimal pH value (5.9) of the Au colloid solution was found to be essential for loading Au NPs onto Al2O3 while avoiding the growth of Au NPs. Au NPs and Au/Al2O3 catalysts were tested in the reduction of p-nitrophenol with NaBH4. Interestingly, the catalytic activity depended on the size of Au NPs, being the highest when the average size was 3.4 nm. Relevant characterization by UV-Vis, TEM, and XRD was conducted.
Highlights
Since Haruta and co-workers discovered that small gold nanoparticles (Au NPs) supported on some reducible oxides can be highly active catalysts for CO oxidation [1,2,3], heterogeneous catalysis by gold has attracted much attention [4,5,6]
The application of gold catalysts in the synthesis of organic chemicals has been the subject of active research recently [7,8,9,10,11]
The catalytic activities of unsupported Au NPs and Au/Al2O3 catalysts with different Au particle sizes were studied for the reduction of p-nitrophenol with NaBH4
Summary
Since Haruta and co-workers discovered that small gold nanoparticles (Au NPs) supported on some reducible oxides can be highly active catalysts for CO oxidation [1,2,3], heterogeneous catalysis by gold has attracted much attention [4,5,6]. Supported gold catalysts were usually prepared by a deposition-precipitation method. Au NPs (colloids) with controllable sizes can be synthesized in a liquid phase, and deposited onto a solid support [12,13,14,15]. Sometimes there exists an optimal particle size for a catalytic system. Laoufi et al [21] investigated the catalytic activity of Au/TiO2 for CO oxidation, and found that the optimum Au particle size was 2.1 ± 0.3 nm. Au NPs with tunable average particle sizes (1.7, 3.4, 5.7, 8.2 nm) were synthesized by reducing HAuCl4 with NaBH4, and loaded onto a commercial Al2O3 support. The catalytic activities of unsupported Au NPs and Au/Al2O3 catalysts with different Au particle sizes were studied for the reduction of p-nitrophenol with NaBH4. An optimal Au particle size of 3.4 nm was identified
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