Elucidation of Pt Clusters in the Micropores of Zeolite Nanoparticles Assembled in Thin Films

Platinum clusters are prepared by gamma radiolysis of beta zeolite suspensions (Pt-Beta) in the presence of a templating agent (tetraethylammonium hydroxide, TEAOH). Further, the Pt-Beta suspensions were stabilized with methyl cellulose and deposited in thin films with a thickness of 220 nm on silicon wafers. Elucidation of the size, distribution, and stability of the Pt clusters in the colloidal suspensions and thin films is provided by high-resolution transmission electron microscopy (HRTEM) combined with grazing incident X-ray diffraction (GI-XRD) measurements. The lateral length of the Pt clusters immobilized in the channels of the beta nanocrystals is between 1 and 2 nm. The presence of crystalline fringes with spacings of 0.23 and 1.26 nm corresponding to cubic Pt and zeolite beta are clearly seen in the HRTEM. The homogeneous distribution of the clusters along the film thickness is confirmed by GI-XRD measurements at two penetration depths. Besides, the location of the Pt clusters in the channels of beta nanoparticles is studied by FTIR spectroscopy. The Pt clusters confined in the channels of beta crystals decrease the total micropore volume and also lower the water sorption capacity in comparison with pure beta zeolite.