MSc seminar

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Photo Catalytic Reduction of CO2

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INTRODUCTION
 CO2 – A Serious Threat
 Greenhouse Gas
 Sources – Industrialization , burning of fossil
fuels , deforestation.
 CO2 – 76 % of the total greenhouse gases.
Pie chart showing the amounts of various
greenhouse gases in the atmosphere.

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WHY CO2 REDUCTION IS IMPORTANT
 Increase in globe’s temperature.
 Melting of glaciers.
 Rise in sea level.
 Potent source of biofuel.
Graph showing the rapid increase of CO2 from year to year
Melting of ice due to global warming.

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HOW CO2 REDUCTION TAKES PLACE
 By the use of photocatalyst which uses solar
radiation as the renewable source of energy.
 Inorganic Semiconductors (ISs) such as
metal oxides , TiO2 is used as photocatalyst
for the purpose.
 But use of this Inorganic Semiconductors
also holds certain disadvantages.
 Use of hybrid doped semiconductors and
conjugated polymers can enhance the
efficiency of photocatalyst.

5. STABILITY OF CO2
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 CO2 is a very much Thermodynamically stable symmetrical
molecule.
From Gibbs–Helmholtz relationship
∆G0 =∆H0 − T∆S0
Free energy of formation of CO2 is -394.0 KJ/mol.
 Reduction of CO2 is highly endothermic reaction.
Reduction potential of CO2 / CO2
•− = -1.65v

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FLOWCHART OF CO2 REDUCTION
Absorb light from
solar spectrum
Excitation of electron from
valence band to conduction band
Formation of
electron-hole pair
Transfer to the
photocatalyst surface
React with the adsorbed
molecules

7. CATALYST FOR CO2 REDUCTION
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SEM image of TiO2 nanoparticles
•TiO2 is worldwide used as
photo catalyst
• It have Hollow Sphere ,
Ultrathin Nanosheet structure
• No toxicity , Photocorrosion
resistance

8. DISADVANTAGE OF TiO2
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 TiO2 band gap is 3.2eV.
 Limits its absorption in the
Ultra Violate region.
 It is only the 8 % the entire
solar spectrum.
 So the catalyst demands modification.

9. NANOCOMPOSITES MATERIALS
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 TiO2 is coupled with CuxO, to produce
mesoporous , hetero -structure composits.
 Band gap of CuxO is 1.35-1.7 eV
 CuxO works as p-type semiconductor and
TiO2 works as n-type semiconductor .
 It is works as intrinsic semiconductor.
 Absorbs light in the 600−1000 nm range.

10. CATALYTIC PATHWAY
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11. PICTORIAL REPRESENTATION OF
SYNTHESIS OF COMPOSITES
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12. SYNTHESIS OF DIFFERENT
COMPOSITES
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Sample Amount
of
Cu/Cu2O
(ml)
Amount
of TiCl4
(ml)
SBET
(m2·g−1)
pore
volume
(cm3·g−1)
Band gap
(eV)
CT03 20 0.3 11.05 0.115 3.09
CT05 20 0.5 16.49 0.102 3.12
CT07 20 0.7 26.95 0.094 3.15
CT09 20 0.9 22.95 0.164 3.2

13. CHARACTERIZATION OF COMPOSITES
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Further sample was characterized by XRD, TEM , FE-SEM
technique
XRD patterns
TEM Image
FE-SEM

14. CHARACTERIZATION BY
PHOTOLUMINSCENSE(PL) SPECTRA
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PL emission spectra of pure TiO2, Cu/Cu2O
nanocomposites,
and the sample CT07
• Pure TiO2 depicts a sharp peak
around 385 nm
• Cu/ Cu2O exhibit a UV emission
peak at 380 nm
&
visible emission peak at 520 nm

15. RESULTS
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UV−vis DRS of all samples
Rates of CH4 evolution

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CONJUGATED POLYMERS
Increases specific surface area
Chemically stable.
Increase charge transfer photo inducibly.
Nanoscale porosity for adsorption of CO2 molecules.
Structural diversity to play as selective CO2 adsorbent.
By developing organic-inorganic hybrid (OIH) materials.
OIH materials can be organic dyes, organic macromolecules
or polymers able to sensitize ISs.
Why it is used?
How it is used?

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HOW CHARGE TRANSFER INCREASES
REF:- DOI:10.1002/cctc.201801046

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WHY VISIBLE LIGHT IS IMPORTANT
Distribution of Energy from the Sun
Visible Light – 39%
UV – 8%
IR – 53%
REF:- MC-GRAW HILLS EDUCATION

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CONJUGATED POROUS POLYMERS
POLYANILINE (PANI)
REF: - DOI: 10.1039/c9cs00377k

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SYNTHESIS OF POROUS MOLECULES
Polycondensation reactions like free-radical
polymerization
Schiff-base condensation
Thermal/chemical substitution reactions
Friedel-Craft reactions – mesopores type polymers
Metal catalyzed C-C bond formation
Homo/cross-coupling reactions

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CLASSIFICATION OF POROUS
MATERIALS
MESOPOROUSMICROPOROUS MACROPOROUS
< 2 nm
Example- Zeolite,
Activated charcoal
2 - 50 nm
Example- Carbon
Materials, Ceramics
> 50 nm
Example- Gel, Foam,
Cross linked
polyelectrolytes
Conjugated polymer inorganic hybrid materials can be
mesoporous or microporous.

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MECHANISM OF ELECTRON
TRANSFER
REF: - DOI: 10.1039/c9cs00377k
IS
CP

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HOW HYBRID MATERIALS ARE MADE
REF: - DOI: 10.1039/c9cs00377k

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RESULTS
0.85% PANI–TiO2 hybrid
photocatalyst shows rates of CO, CH4
and H2 formation 2.8, 3.8 and 2.7
times higher than TiO2.
Pt–0.85% PANI–TiO2 photocatalyst,
led to H2 and CH4 production 3.3 and
2.8 times higher than those achieved
over the Pt–TiO2 catalyst.
REF :- DOI: 10.1039/C5CC05113D

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CONCLUSION
 This technology effectively converts the pollutant (CO2) into various
important raw materials and biofuels which can be further used as
a renewable green source of energy.
 Porosity and stability of the photocatalysts can also be modified by
tuning various paramaters and also trying different metal ions.
 Increase in rate of reaction on using MOF.
 Hold the potential to revolutionize the future and cater to the needs
of future generarions.
Methanol being used as bio-fuel
Figure showing reduction process in MOF

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REFERENCE
(1) Hybrid CuxO−TiO2 Heterostructured Composites for Photocatalytic CO2
Reduction into Methane Using Solar Irradiation: Sunlight into Fuel
Seung-Min Park,† Abdul Razzaq,† Young Ho Park,† Saurav Sorcar,† Yiseul Park,‡
Craig A. Grimes,§ and Su-Il In*,† ACS Omega 2016, 1, 868−875
(2) Improving the photocatalytic reduction of CO2 to CO for TiO2 hollow spheres
through hybridization with a cobalt complex
† Jinliang Lin, *a Xiaoxiang Sun,b Biao Qina and Ting Yua, RSC Adv., 2018, 8, 20543
(3) Hybrid materials based on conjugated polymers and inorganic semiconductors as
photocatalysts: from environmental to energy applications
Marta Liras, * Mariam Barawi and Vı ´ctor A. de la Pen˜a O’Shea *, Chem. Soc. Rev.,
2019, Advance
(4) Functional Conjugated Polymers for CO2 Reduction Using Visible Light
Can Yang,[a] Wei Huang, [b] Lucas Caire da Silva,[b] Kai A. I. Zhang,*[b] and Xinchen
Wang*[a], Chem. Eur. J. 2018, 24, 17454 – 17458

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