Solar simulated hydrogen evolution using cobalt oxide nanoclusters deposited on titanium dioxide mesoporous materials prepared by evaporation induced self-assembly process.

Cobalt-contg. TiO2 mesoporous materials were prepd. by Evapn.-Induced Self-Assembly (EISA) process. The resulting mesoporous materials were characterized using powder X-ray diffraction (XRD), nitrogen physisorption, Raman spectroscopy, diffuse reflectance spectroscopy (DRS), transmission electron microscopy (TEM), XPS, and photoluminescence spectroscopy (PL). The photocatalytic activities of the mesoporous materials were investigated for hydrogen prodn. under solar simulated conditions. The non-modified TiO2 sample produced only 4 μmole H2/g catalyst after 4 h of irradn. In contrast, the Co contg. mesoporous materials produced significantly higher amts. of hydrogen under identical conditions. The highest solar hydrogen evolution (634 μmole H2/g catalyst after 4 h of irradn.) was from the Co-TiO2-0.5 material. The physico-chem. characterization results indicate that the Co2+ ions are dispersed as oxide species on the surface of the mesoporous titania. These cobalt surface species act as trap sites preventing recombination of the charge carriers as shown by PL measurements. The addn. of Co2+ ions to the synthesis mixt. prevents the formation of anatase-to-rutile which favorably permits more solar hydrogen prodn. [on SciFinder(R)]