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

Abstract

The photocatalytic production of H₂ from water splitting was demonstrated on Ni/NiO/KNbO₃/CdS nanocomposites using visible light irradiation at wavelengths >400 nm in the presence of isopropanol. The inherent photocatalytic activity of bulk-phase CdS was enhanced by combining Q-sized CdS with KNbO₃ and Ni deposited on KNbO_3. Enhanced activity is most likely due to effective charge separation of photogenerated electrons and holes in CdS that is achieved by electron injection into the conduction band of KNbO₃ and the reduced states of niobium (e.g., Nb(IV) and Nb(III)) are shown to contribute to enhanced reactivity in the KNbO₃ composites by mediating effective electron transfer to bound protons. We also observed that the efficient attachment of Q-size CdS and the deposition of nickel on the KNbO₃ surface increases H₂ production rates. Other factors that influence the rate of H₂ production including the nature of the electron donors and the solution pH were also determined. The Ni/NiO/KNbO₃/CdS nanocomposite system appears to be a promising candidate for possible practical applications including the production of H₂ under visible light.