Oxidation of CO and H2 by O2 and N2O on Au/TiO2 catalysts in microreactors

We performed steady-state activity measurements in microreactors to obtain the reaction rates for CO and H2 oxidation. These reactions were studied on three different gold particle sizes (d≈3.6,5.7,16.2 nmd≈3.6,5.7,16.2 nm) using either O2 or N2O as oxidizing agents. From our TEM analysis, our CO oxidation rates follow the d−3 relationship proposed in Hvolbæk et al. [B. Hvolbæk, T.V.W. Janssens, B.S. Clausen, H. Falsig, C.H. Christensen, J.K. Nørskov, Nano Today 2 (2007) 14–18]. Density functional theory (DFT) calculations on a Au{532} surface and a Au12 cluster, which model corner sites, reproduced the apparent activation barriers of about 37 kJ mol−1 for CO oxidation on the smallest nanoparticles by both O2 and N2O. For all of the reactions studied, we found the overall activation barrier depended only on the size of the TiO2 supported gold nanoparticle.