Xafs investigation of nanopaticles supported on faujasite: Effect of hydrogen chemisorption on the atomic structure

Extensive studies oil the supported metal nanoparticles have been carried out due to their unique physicochemical and electro-magnetic characteristics in many industrial applications, especially for heterogeneous catalytic processes. Of great importance has been an atomic structural change of the well-defined metal nanoparticle during catalysis. The structural change of metal bond was qualitatively formulated with the in-situ X-ray absorption fine structure data, using hydrogen molecule as a probe for 1 -nm sized Pt, Pd, Rh, Ir and Ru particle entrapped in the faujasite-type zeolite consisting of similar to 50 atoms. This study elucidated that the maximum occupied metal-metal bonding state can be classified into two categories, the bonding orbital for Ru, Rh and Pd nanoparticle and the antibonding orbital for Pt and It nano particle, referred from change of a damping parameter, the Debye-Waller factor upon hydrogen adsorption. It was also shown that the structural integrity of the Pd and Ru nanoparticle was reformed with hydrogen adsorption, so called the adsorbateinduced restructuring.