Chapter Conclusion In this thesis supported nanogold catalysts on low temperature CO oxidation are intensively studied. Three types of easily reduced oxides, i.e. iron oxides, titanium oxides and copper oxide are used as the support. Also three preparation methods, i.e. coprecipitation, deposition-precipitation, and colloid-based impregnation are employed for preparing Au catalysts with Au particle size around 2-4 nm. The performance of Au/iron oxide catalysts towards PROX reaction was found to be strongly affected by catalyst preparation and post-treatment. Among the three methods studied in this chapter, the colloid-based method is better than the co-precipitation and deposition-precipitation methods. The AuCH sample (Au catalyst supported on Fe2O3 prepared by the colloidbased method) showed the highest activity, selectivity and stability at temperatures between RT and 100oC. The reaction rate rco for the CO+O2CO2 at 25oC was measured to be 12.3 x 10-4 molco* gAu-1* S-1, better than that reported in literature, i.e. 4.87 * 104 molCO g-1 AuS-1 for Au/-Fe2O3, provided by the World Gold Council. With the colloid- based method, Au particle size and distribution can be better controlled. Provided that gold particles in all the four Au/iron-oxide samples prepared by various methods are small enough to be able to activate CO and O2, the CO oxidation activity was found to remarkably depend on the structure of the iron oxide support, in the order: ferrihydrite > hematite > magnetite. XRD, TPR, XPS and SIMS studies showed the presence of OH and COO groups on the AuCH samples. Moreover, non-metallic Au has been detected in 181 the AuCH sample in addition to metallic Au. All these would contribute to the enhanced activity of the AuCH sample. In Chapter Au supported on six different types of TiO2 are studied. Compared to the commercial anatase TiO2(CB) and kinds of TiO2 samples from KAISHA Ltd, the home-made TiO2 nanotubes (NT) are better catalyst support, on which the Au nanoparticles exhibit significantly improved catalytic activity for the CO oxidation at room temperature. Surface area is found to be an important factor for catalysts’ activity, since higher surface area samples show higher activity. However, Au/TiO2 (NT) and Au/MC150, one of the Kaisha samples, have similar surface areas but exhibit remarkably different activity. In depth studies in this chapter showed that TiO2 nanotubes are a better support because they have smaller sizes ( . oxide – one of the earliest and most investigated support for gold nano particles is chosen as the support. Although both experimental and theoretical researches concerning the effect of gold nanoparticle’s. determine the nature and structure of the active center over the nano -gold catalysts: whether bi-layer gold cluster is essential for CO oxidation, what are the gold oxidation states under reaction. derivation of a reaction mechanism similar to those proposed by G.C. Bond and H.H. Kung. All these results provide deep insights on the gold catalysis and valuable guidance for future study of it. In