A rapid and efficient method to deposit gold particles on catalyst supports and its application for CO oxidation at low temperatures

A rapid, simple, and efficient method for the preparation of highly dispersed supported An catalysts has been developed. In the preparation, NaBH4 is used to reduce the An precursor, lysine is employed to cap the formed An colloids, and a short sonication time is applied to facilitate dispersion and deposition of the An colloids onto the catalyst support, which has been mixed with the precursor beforehand. The end-point pH value of the solution and the isoelectric points (IEPs) of the catalyst supports have an influence on the size of the An particles and their deposition. The optimum value for the end-point pH is 7.5-10.0, and the IEP should be 5-10. The amino acid capping agent is easily removed at the catalyst activation stage at 200 degrees C, and the Au particles are thermally stable against sintering, even at 500 degrees C for 3 h. It is also proven that the method is applicable to the preparation of supported Pt catalysts. The catalytic activity of the prepared An catalysts for CO oxidation in the absence/presence of H-2 is comparable to that of a An catalyst prepared by the co-precipitation (CP) method, and to that of the standard catalyst from the World Gold Council (WGC). X-ray photoelectron spectroscopy (XPS) results show that only metallic An exists in the catalysts before and after activation, and also after the catalysis reaction.