Photocatalytic production of H2 on Ni/NiO/KNbO3/CdS nanocomposites using visible light

COLL 413

Jina Choi, choi@caltech.edu1, Su Young Ryu1, William Balcerski1, and Michael R. Hoffmann, mrh@caltech.edu2. (1) Engineering and Applied Science, California Institute of Technology, 1200 East California Blvd., Pasadena, CA 91125, (2) Environmental Science and Engineering, California Institute of Technology, W. M. Keck Laboratories 138-78, 1200 E. California Blvd., Pasadena, CA 91125
The efficient production of molecular hydrogen from the water on the surface of a complex Ni/NiO/KNbO3/CdS nanocomposite has been achieved with visible light irradiation (>400 nm). The relative low photocatalytic activity of CdS was enhanced by combining Q-sized CdS with KNbO3, Ni and NiO deposited on the KNbO3 surface. An unusual high quantum efficiency for H2 production obtained with the KNbO3/CdS composites may be due to effective charge separation of electrons and holes photo-generated in CdS with the visible light achieved by electron injection into the conduction band of KNbO3. In addition, reduced states of niobium (e.g., Nb(IV) and Nb(III)) appear to play a role in enhancing reactivity in the KNbO3 composites by providing alternative electron transfer pathways. In addition, the overall pathway to H2 also includes the photoreduction of Cd(II) to Cd(0) on surface of Q-CdS. Production rates are also enhanced in mixed water-alcohol solvents. Alcohols (methanol, ethanol, isopropanol, etc.) serve as alternative electron donors and they modified the near surface environment via electrical double layer compressionr which is correlated to the dielectric constant of the mixture.

 

Environmental Interfaces
2:00 PM-6:10 PM, Tuesday, 12 September 2006 Sir Francis Drake -- Empire Room, Oral

Division of Colloid & Surface Chemistry

The 232nd ACS National Meeting, San Francisco, CA, September 10-14, 2006