Photocatalytic hydrogen production with visible light using nanocomposites of CdS and Ni on niobium oxide

• Niobium oxide composite catalysts are synthesized and characterized.
• Photocatalytic production of H2 at λ > 420 nm using CdS and Ni on K4Nb6O17.
• CdS undergoes oxidation state changes during irradiation.

Niobium oxides (KNbO3, K4Nb6O17) were combined with nano-particulate CdS and Ni to form composite photocatalysts that are able to produce H2 gas from water/ethanol solutions under visible light illumination. Ni doping was shown to affect the Nb–O bonding states, and to compete with Cd for ion exchange sites, although the Ni/CdS-doped catalysts still were found to have higher photo-catalytic activity than composite potassium niobates with nanoparticle CdS deposits alone. XPS studies showed the loss of excess Cd2+, but not sulfur, during the course of the photoreaction for the KNbO3 support matrix, but significant loss of both Cd and S for the K4Nb6O17 support.