Assembly of Nanoparticles in Zeolite Y for the Photocatalytic Generation of Hydrogen from Water

Synthesis of nanoparticles of TiO 2, Pt, CdS, and their binary and ternary combinations were made on zeolite Y starting from molecular precursors that are ion exchanged into the zeolite. Nanoclusters of TiO 2 in the anatase form were formed from titanyl ions at low loadings of Ti (1 per 2.5 supercages). CdS (hexagonal form) and metallic Pt were formed from Cd 2+ and Pt(NH 3 ) 4 2+ ion exchanged into the zeolite. Binary clusters of TiO 2 −Pt and TiO 2 −CdS were also synthesized. Electron microscopy and elemental analysis suggests colocalization of the distinct nanoparticles. Photocatalytic H 2 evolution is the strongest indicator of colocalization, since improvements in H 2 evolution rates of ∼100 for Pt/TiO 2 -zeolite over TiO 2 -zeolite and ∼18 for CDS/TiO 2 -zeolite Y over CdS-zeolite Y were observed. These improvements exceed colloidal binary systems reported in the literature. However, improvements in the H 2 evolution rate of the ternary system Pt/CdS/TiO 2 was not as marked, as compared to the best colloidal ternary systems reported in the literature. A model is proposed that explains the colocalization of nanoparticles, mediated by the zeolite via a self-assembly process. This model also explains why the ternary system is not optimal; since the Pt needs to be associated only with TiO 2 for best H 2 evolution, and the zeolite-based assembly promotes a statistical colocalization of the three nanoparticles.