Efficient Visible-light Photocatalytic Hydrogen Research Articles

Eosin Y-sensitized ZnO/TiO2 for efficient visible light photocatalytic hydrogen evolution

ABSTRACTIn this work a series of Eosin Y-ZnO(x%)/TiO2 were prepared. ZnO well dispersed on the surface of TiO2, which improves the adsorption of Eosin Y and the excited electron to transfer to the conduction band of TiO2. Therefore the visible light activity of 0.2%Pt-Eosin Y-ZnO(x%)/TiO2 is much higher than that of the 0.2%Pt-Eosin Y-TiO2 and 0.2%Pt-Eosin Y-ZnO. The 0.2%Pt-Eosin Y- ZnO(1.5%)/TiO2 has the highest visible light activity among the catalysts coupled with various ZnO amount, whose activity is increased by a factor of 3.5 compared to that of 0.2%Pt-Eosin Y-TiO2. It is proposed that, 0.2%Pt-Eosin Y-ZnO(1.5%)/TiO2 has the optimal trapping sites of carriers and thickness of the space-charge layer on the TiO2 particle surface, so these factors result a more efficient charge separation, an increased lifetime of the charge carriers, and the enhanced of hydrogen production .

Formation of multilayer-Eosin Y-sensitized TiO2 via Fe3+ coupling for efficient visible-light photocatalytic hydrogen evolution

An efficient visible-light active photocatalyst of multilayer-Eosin Y-sensitized TiO2 is prepared through linkage of Fe3+ between not only TiO2 and Eosin Y but also different Eosin Y molecules to form three-dimensional polymeric dye structure. The multilayer-dye-sensitized photocatalyst is found to have high light harvesting efficiency and photocatalytic activity for hydrogen evolution under visible light irradiation (λ > 420 nm). On the optimum conditions (1:1 initial molar ratio of Eosin Y to Fe(NO3)3, initial 10 × 10−3 M Eosin Y, and 1.0 wt% Pt deposited by in situ photoreduction), its maximal apparent quantum yield for hydrogen evolution is 19.1% from aqueous triethanolamine solution (TEOA aq). The present study highlights linking between dye molecules via metal ions as a general way to develop efficient visible-light photocatalyst.

THIRD ORDER NONLINEAR EFFECT NEAR A DEGENERATE BAND EDGE

We describe the properties of a 1D anisotropic periodic structure, designed to have a band edge with fourth order degeneracy, called a degenerate band edge (DBE). A giant field resonance at the transmission peak frequency closest to this band edge has been verified by rigorous numerical calculation and is supported by experimental evidence. Simulations are presented of the consequences of a χ3 nonlinear index change at a DBE resonant frequency which can provide all-optical switching and transmission self-limiting.

Eosin Y-sensitized nitrogen-doped TiO 2 for efficient visible light photocatalytic hydrogen evolution

A nitrogen-doped TiO 2 (N-TiO 2) photocatalyst was prepared by the calcination of the hydrolysis product of Ti(SO 4) 2 with aqueous ammonia. Pt was loaded on N-TiO 2 by photodeposition method. A dye-sensitization photocatalyst was prepared by impregnation method with Eosin Y and the platinized N-TiO 2. The prepared samples were characterized by XRD, UV–vis diffuse reflectance spectra (DRS), BET and FT-IR. The visible light activity of the sensitization photocatalysts was evaluated by photocatalytic hydrogen evolution ( λ > 420 nm) in the presence of electron donor triethanolamine (TEOA). The N-TiO 2 has smaller crystalline size and larger specific surface area to enhance the adsorption amount of Eosin Y than TiO 2 prepared by NaOH. Surface oxygen defects produced by nitrogen doping would improve the adsorption of Eosin Y and excited electron to transfer to the conduction band of N-TiO 2. Therefore the visible light activity of the sensitized nitrogen-doped platinized TiO 2 is much higher than that of the sensitized platinized TiO 2. The sensitized nitrogen-doped platinized TiO 2 calcined at 300 °C has the highest visible light activity among the catalysts calcined at various temperatures, whose activity is increased by a factor of 3 compared to that of the sensitized platinized TiO 2 calcined at the same temperature.