AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Atomically-dispersed Pd on Nanostructured Titania for NO Removal by Solar Light
Kakeru Fujiwara, SOTIRIS E. PRATSINIS, ETH Zurich
Abstract Number: 80 Working Group: Nanoparticles and Materials Synthesis
Abstract Aerosol technology is uniquely positioned for large scale synthesis of noble metal sub-nano clusters on ceramic supports that can lead to enhanced catalyst performance with minimal use of noble metals. So Pd clusters onto nanostructured TiO2 particles are prepared in one step while controlling the Pd cluster size from a few nanometers down to that of single atoms. Under solar light irradiation, these materials remove NOx 3 or 7 times faster than commercial TiO2 (P25, Evonik) with or without, respectively, photo-deposited Pd on it (ACS Catalysis, 2016, 6:1887-1893). Annealing such materials leads to solar photocatalytic NOx removal in a standard ISO reactor up to 10 times faster than that of commercial TiO2. Such superior performance can be attained by only 0.1 wt% Pd loading on TiO2. Annealing these flame-made powders decreases the amorphous TiO2 fraction and increases its crystal and particle sizes while single Pd atoms and clusters are stable up to, at least, 600 C for 2 hours in air but at 800 C they grow into PdO nanoparticles whose fraction is comparable with the nominal Pd loading proving the presence of Pd atoms on the catalysts surface along with STEM analysis. Diffuse Reflectance Infrared Fourier Transform Spectroscopy reveals NO adsorption on single, double, 3- and 4-fold coordinated Pd atoms depending on their flame concentration and annealing conditions. The peak intensity of NO adsorption sites involving multiple Pd atoms is substantially lower in TiO2 with 0.1 than 1 wt% Pd but that intensity from single Pd atoms is comparable. This indicates the dominance of isolated Pd atoms compared to their clusters in Pd/TiO2 containing 0.1 wt% Pd that match or exceed the photocatalytic NOx removal at higher Pd contents proving the potential of flame-depositing of Pd atoms.