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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!