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

Abstract

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).

Synthetic Approaches to Colloidal Nanocrystal Heterostructures Based on Metal and Metal-Oxide Materials

“…Less frequently, an opposite reaction scheme has been proposed, where CNC seeds of the target metal are utilized to promote heterogeneous nucleation and accommodate growth of anisotropic-shaped sections of a semiconductor compound [ 330 ]. Building upon on this synthetic success, the development of several prototypes of CNHSs based on metal and metal-oxides has been pursued, yet a comparatively lower degree of configurational control has generally been achieved [ 331 , 332 , 333 , 334 , 335 , 336 , 337 , 338 , 339 , 340 , 341 , 342 , 343 , 344 , 345 , 346 , 347 , 348 ]. Relevant cases are illustrated in Figure 10 and Figure 11 .…”

Hydrogen evolution via noble metals based photocatalysts: A review

“…Upon deposition of metallic Ag nanoparticles on CaTiO3, hydrogen generation rate has been increased, because of the stimulation of surface plasmon resonance (SPR) in silver, increased e -/h + separation in CaTiO3 and narrowing of the bandgap in CaTiO3. Recently, silver was utilized on the TiO2, and silica was used to provide the highest number of surface sites, and calcination was performed on it at the optimum temperature and for the appropriate time [110]. Hydrogen generation rate on silicasupported Ag-TiO2 is 4.5 and 10 times greater than calcined TiO2/SiO2 and uncalcined TiO2/SiO2 respectively.…”

“…Ru atoms/multi-edged TiO2 spheres Solvothermal method and calcination of as-synthesized ME-PT, 20 ml of methanol, Xe lamp, 300 W 7.2 mmolg -1 h -1 [105] Rh-doped Ca2Nb3O10 sheet Thermal annealing, 10 vol % CH3OH, xenon lamp 500 W 77 mmolg -1 h -1 [106] Ag/CaTiO3 "One-pot" synthesis, medium pressure Hg lamp 450 W, 20 min, 10 vol% solution of glycerol 167 μmolg -1 h -1 [109] Ag−TiO2/SiO2 Hydrothermal approach, 2 mL of methanol and 10 mL of water, Xe Arc lamp 150 W, Ar gas 738 μmolg -1 h -1 [110] Ag@Ni/TiO2 One-step photoinduced deposition, four 365-nm LEDs (23.0 mW cm −2 ), 20 min, D-520 Nafion and ethanol (1:1)…”

Recent Advances on Plasmon-enhanced Titania Nanocatalysts for Photocatalytic Degradation of Organic Dyes

“…Hoefelmeyer and co-workers reduced silver nitrate solution using oleylamine and 1,2hexadecanediol in the presence of oleic acidstabilized anatase TiO2 nanorods resulting in the generation of Ag-TiO2 hybrid nanocrystals (HCNs) [52]. The number and size distribution of Ag NPs could be tailored based on the Ag:TiO2 ratio in the synthesis mixture and the choice of the reducing agent.…”

“…Recently, MO's photodegradation is commonly done via the advanced oxidative process (AOP), where plasmon-enhanced titania nanocatalysts are used as the catalytic materials. For instance, Vandarkuzhali et al synthesized mesoporous TiO2-based materials combined with Ag and Au for efficient photodegradation of MO [52]. According to the report, Ag-TiO2 and Au-TiO2 with mesopores structure have a higher photodegradation efficiency with shorter reaction times.…”