Au-CeO2-based nanocatalysts supported on SBA-15 for preferential oxidation of carbon monoxide (PrOx-CO)
In this work, as-synthesized SBA-15 was used as a support for CeO2 and Au nanoparticles (NPs), in order to stabilize them and to promote the metal/oxide interface contact. CeO2 NPs were grown within the pores of SBA-15 using the method of successive metalorganic impregnation-decomposition cycles (IDC), and samples with increasing number of IDCs (x = 2, 5 and 8) were obtained. This method allowed control of the SiO2/CeO2 ratio and tailoring of samples with different crystallite sizes (2-4 nm). The (x)CeO2/S15 supports were then decorated with Au NPs through the Deposition-Precipitation (DP) method using NaOH. The DP conditions used along with the pore size limitations from each support allowed control over the Au NPs size (4 - 9 nm). The samples were characterized by N2 physisorption, XRD, TEM, ICP-OES, XRF, DRS, Raman Spectroscopy and for its catalytic activity for PrOx-CO. The pure supported Au-catalyst exhibited maximum CO conversion at 300 °C. The incorporation of CeO2 reduced the reaction temperature to as low as 100 ºC, while the peak performance for CO conversion was observed for the catalyst containing Au and 5 IDCs of CeO2 (2.0 mol of CO2 formation per mol of Au per second at 135 °C). Further increasing the amount of CeO2 (8 IDC) resulted, however, in a decrease of the catalytic activity, resulting in a substantial reduction of the surface area and subsequent reduced access of the reaction gases (H2, CO, O2) to the active sites of the catalyst.