2 research outputs found
Water-gas shift reaction on Pt/Ce1- xTixO 2-δ: The effect of Ce/Ti ratio
Pt nanoparticles (1.2â2.0 nm size) supported on Ce1âxTixO2âδ (x = 0, 0.2, 0.5, 0.8, and 1.0) carriers synthesized by the citrate solâgel method were tested toward the waterâgas shift (WGS) reaction in the 200â350 °C range. A deep insight into the effect of two structural parameters, the chemical composition of support (Ce/Ti atom ratio), and the Pt particle size on the catalytic performance of Pt-loaded catalysts was realized after employing in situ X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM) and HAADF/STEM, scanning electron microscopy (SEM), in situ Raman and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopies under different gas atmospheres, H2 temperature-programmed reduction (H2-TPR), and temperature-programmed desorption (NH3-TPD and CO2-TPD) techniques. The 0.5 wt % Pt/Ce0.8Ti0.2O2âδ solid (dPt = 1.7 nm) was found to be by far the best catalyst among all the other solids investigated. In particular, at 250 °C the CO conversion over Pt/Ce0.8Ti0.2O2âδ was increased by a factor of 2.5 and 1.9 compared to Pt/TiO2 and Pt/CeO2, respectively. The catalytic superiority of the Pt/Ce0.8Ti0.2O2âδ solid is the result of the supportâs (i) robust morphology preserved during the WGS reaction, (ii) moderate acidity and basicity, and (iii) better reducibility at lower temperatures and the significant reduction of âcokingâ on the Pt surface and of carbonate accumulation on the Ce0.8Ti0.2O2âδ support. Several of these properties largely influenced the reactivity of sites (k, sâ1) at the Ptâsupport interface. In particular, the specific WGS reaction rate at 200 °C expressed per length of the Ptâsupport interface (Îźmol CO cmâ1 sâ1) was found to be 2.2 and 4.6 times larger on Pt supported on Ce0.8Ti0.2O2âδ (Ti4+-doped CeO2) compared to TiO2 and CeO2 alone, respectively.The European Regional Development Fund, the Republic of Cyprus, the Research Promotion Foundation of Cyprus, and the Research Committee of the University of Cyprus are gratefully acknowledged for their financial support through the project TEXNO/0308(BE)/05. S.B. acknowledges financial support from the COST Action CM1104.Peer Reviewe