Photocatalytic reduction of CO2

with TiO2-based semiconductor catalyst

Reporter: Xiang Tianyu Supervisor: Xin Feng

1.Summary of Literatures• TiO2 has been proved to be one of the most

effective and suitable photocatalyst.• Presently, the energy conversion efficiency is still

low, mainly due to the following reasons: (1)Recombination of photo-generated electron/hole pairs.

(2)Inability to utilize visible light. anatase--3.2eV--387.5nm rutile--3.0eV--413.3nm

• The mixed phase TiO2 nanocomposites involved synthesis of rutile nanocrystals in the presence of commercially anatase powder.

• Sintered at 373K and 773K respectively.

Gonghu Li et al. / Synthesizing mixed-phase TiO2 nanocomposites using a hydrothermal method for photo-oxidation and photoreduction applications

Fig. 1. Normalized absorbance of methylene blue at 660 nm as a function of reaction time during photocatalytic oxidation under UV illumination.

• Theoretical and experimental studies indicate that the (001) surface of anatase TiO2 is much more reactive than the thermodynamically more stable (101) surface

• Titanate nanotube—ethanol/hydrofluoric acid solution (40%)--hierarchical flower-like TiO2 superstructures (HFTS)

XIANG Quanjun et al. / Photocatalytic Activity of Hierarchical Flower-Like TiO2 Superstructures with Dominant {001} Facets

Fig. 2. SEM images of the products obtained at different reaction times: (a)0, (b)3, (c)6, and (d)24 h.

Fig. 3. (a) Comparison of the photocatalytic activity of HFTS, TSTP, and P25 for photocatalytic decomposition of acetone in air. (b) Dependence of produced CO2 concentration on irradiation time for HFTS, TSTP, and P25. The inset in (a) shows a schematic illustration of multireflections within the inter-meshed nanosheets.

Fig. 4. The procedure of catalysts preparation.

Slamet et al. / Photocatalytic reduction of CO2 on copper-doped Titania catalysts prepared by improved-impregnation method

• Since the band-gap becomes large with decreasing the size of the particle, both the oxidizing power and reducing power of the photocatalyst becomes great with decreasing the size of the photocatalyst.

• With decreasing the particle size, the total surface area of the photocatalysts per weight unit increases

• The affinity of adsorbing CO2 onto photocatalyst surfaces seems to become high with decreasing particle size

Hiroshi Yoneyama / Photoreduction of carbon dioxide on quantized semiconductor nanoparticles in solution

• The first factor does not play an important role in the apparent increase of photocatalytic activities with decreasing the particle size

• The increase in the photocatalytic activities with decreasing the particle size was more than the increase in the surface area, suggesting that the increase of the surface area alone cannot explain well the apparent increase in the photocatalytic activities observed

• The third factor is involved in the apparent enhancement of the photocatalytic activities with decreasing the particle size

• The optimum particle size corresponding to the highest yields of both products was 14 nm. The observed optimum particle size is a result of competing effects of specific surface area, charge–carrier dynamics and light absorption efficiency.

K. KocˇI et al. / Effect of TiO2 particle size on the photocatalytic reduction of CO2

• It was found that at ≥0.05% TiO2 concentration, the methane yield reached an optimum value.

G.R.Dey et al./Photocatalytic reduction of carbon dioxide to methane using TiO2 as suspension in water

G.R.Dey et al./Photocatalytic reduction of carbon dioxide to methane using TiO2 as suspension in water

Fig. 5 The influence of NaOH concentration on the photocatalytic reduction of carbon dioxide.

Fig. 6 The influence of the irradiation time on the photocatalytic reduction of carbon dioxide. Shaohua Liu et al./Photocatalytic reduction of carbon dioxide using sol–gel derived titania-supported CoPc catalysts

• The study attempts to produce O2 and H2 from a WO3+Ce4+ suspension in two consecutive processes. Initially, water is oxidized photocatalytically to oxygen and proton using photogenerated valence band holes,with the simultaneous traping of the conduction band electrons by ceric cations,which are subsequently reduced to cerous species.This is followed by the reduction of protons or water to hydrogen in a photochemical process that involves the direct photoexcitation of cerous ions.

Gratian R. et al. /The photoinduced evolution of O2 and H2 from a WO3

aqueous suspension in the presence of Ce4+ /Ce3+

• TiCl6+ HCl (6M)--H2TiCl6

H2TiCl6+NH3· H2O + SiC--SiC/TiO2

SiC/TiO2+Cr(NO3)3·9H2O--Cr2O3/SiC/TiO2

Yaojun Zhang et al./Preparation of ternary Cr2O3–SiC–TiO2 composites for the photocatalytic production of hydrogen

Fig. 7. Diffuse reflectance UV–vis spectra of the composites.

Fig.8. The hydrogen-producing activities for the composites by the decomposition of water under visible-light irradiation for 6 h.

Fig. 9. A mechanism for the photocatalytic decomposition of water to produce hydrogen by the Cr2O3–SiC–TiO2 composite.

2. Individual Ideas• N-doped and Pt-loaded TiO2 nanosheet

• Cu2+ doped TiO2--SiC composite semiconductor

• NaOH， Na2S/Na2SO3， Fe2+

• Visible light

THANK YOU!