Photocatalytic Production of Hydrogen from Water with Visible Light Using Hybrid Catalysts of CdS Attached to Microporous and Mesoporous Silicas

Microporous and mesoporous silicas are combined with nanoparticulate CdS particles to form hybrid photocatalysts that produce H2 from water/ethanol solutions under visible light irradiation. Catalyst structures are characterized by XRD and SEM. All hybrid materials are active photocatalysts for water splitting, and the order of photoactivity is found to be zeolite-Y > SBA-15 > zeolite-L. Silica cavity size, which determines, in part, CdS particle size, and photocatalytic activity are found to be correlated. Photocatalytic activity is seen to decrease under acidic or basic conditions with associated negative ionic strength effects. In addition, XPS analysis indicates loss of ion-exchanged and Cd2+ ion from the silicate supports occurs during the course of the photochemical reaction in solution with the complete retention of preformed and surface-bound CdS.