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Published November 7, 2007 | public
Journal Article

Photocatalytic Production of H_2 on Nanocomposite Catalysts


The photocatalytic production of H_2 in water with visible light using nanocomposite catalysts, which include quantum-sized (Q-sized) CdS, CdS nanoparticles embedded in zeolite cavities (CdS/zeolite), and CdS quantum dots (Q-CdS) deposited on KNbO_3 (CdS/KNbO_3 and Ni/NiO/KNbO_3/CdS), is investigated. The rate of H_2 production in alcohol/water mixtures and other electron donors at λ ≥ 400 nm is the highest with the hybrid catalyst, Ni/NiO/KNbO_3/CdS with a measured quantum yield, φ, of 8.8%. The relative order of reactivity as a function of catalyst is Ni(0)/NiO/KNbO_3/CdS > Ni(0)/KNbO_3/CdS > KNbO_3/CdS > CdS/NaY-zeolite > CdS/TiY-zeolite > CdS, while the reactivity order with respect to the array of electron donors is 2-propanol > ethanol > methanol > sulfite > sulfide. In addition, the rates of H_2 production from water and water−alcohol mixtures are correlated with fluorescent emission spectra and fluorescence lifetimes. Irradiation of Ni/NiO/KNbO_3/CdS proceeds via the partial reduction of Cd(II) to Cd(0) on the surface of CdS. The coupling of Ni(0)/NiO and Cd(0) on the surface of KNbO_3 appears to have some of the chemical principles of a Ni/Cd battery at high overvoltages. Evidence for the formation of nickel hydride as an important intermediate has been obtained.

Additional Information

© 2007 American Chemical Society. Received for review February 28, 2007. Revised manuscript received May 1, 2007. Accepted May 3, 2007. Publication Date (Web): June 26, 2007. We are grateful to the Hydrogen Energy R&D Center of the 21st Century Frontier Research and Development Program of the Ministry of Science and Technology of Korea for financial support. Additional support was provided graciously by the Fellowship Program of the Korean Science & Engineering Foundation (KOSEF) and the Davidow Research Fund of the California Institute of Technology.

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October 23, 2023