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 TiO2 nanorods to form Ag–TiO2 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 TiO2 nanorods, P25 TiO2, and Ag–TiO2 HNCs in methanol/water under xenon lamp irradiation. The turnover frequency for hydrogen evolution on silica-supported Ag–TiO2 was 1.4 × 10–4 s–1, greater than that of the anatase TiO2 nanorods (9.8 × 10–6 s–1) or the coupled anatase/rutile TiO2 (P25 catalyst; 5.2 × 10–5 s–1).