Effect of Nickel Oxide Doping to Ceria-Supported Gold Catalyst for CO Oxidation and Water-Gas Shift Reactions

Ceria-supported gold catalyst has drew much research interest owing to its high reactivity on CO oxidation and water-gas shift (WGS) reactions. However, till now, there were relatively limited studies on the effect of secondary metal/metal oxide component into gold-ceria system to enhance its catalytic performance. In this work, we synthetized the ceria supported gold-nickel samples via a deposition-precipitation method with the base of NaHCO3 to adjust final pH value of 8~9. We found that the addition of nickel oxide drove off the gold species from the stock solution during synthesis, and thus resulted in a dramatical decrease on doped Au concentration. No crystallized phases of gold and nickel were observed on the surface of ceria nanorods in both X-ray diffraction (XRD) and transmission electron microscopy (TEM). The valence of nickel was maintained as Ni2+ for all the measured samples by X-ray photoelectron spectroscopy (XPS), while gold was oxidized with the increased nickel amount after analysis of X-ray absorption near edge spectroscopy (XANES). The corresponding catalytic tests showed that with the introduction of nickel oxide, the activity of gold-ceria catalyst was promoted for the WGS reaction, but inhibited for the CO oxidation reaction.