Ag–TiO₂ Hybrid Nanocrystal Photocatalyst: Hydrogen Evolution under UV Irradiation but Not under Visible-Light Irradiation

We report a thermolytic reduction of silver precursors in the presence of anatase TiO 2 nanorods to form Ag–TiO 2 hybrid nanocrystals (HNCs). Upon changing the reaction conditions, the size and number density of Ag on the HNCs could be adjusted. The size and number density of Ag on the HNCs were found to have an inverse relation. We assess the hydrogen evolution of TiO 2 nanorods, P25 TiO 2, and Ag–TiO 2 HNCs in methanol/water under xenon lamp irradiation. The turnover frequency for hydrogen evolution on silica-supported Ag–TiO 2 was 1.4 × 10 –4 s –1, greater than that of the anatase TiO 2 nanorods (9.8 × 10 –6 s –1 ) or the coupled anatase/rutile TiO 2 (P25 catalyst; 5.2 × 10 –5 s –1 ).