Photocatalytic reduction of carbon dioxide

MSc seminar

1. Srijan Mukherjee , Shubhradip Guchait & Subhajit Das

2. INTRODUCTION CO 2 – A Serious Threat Greenhouse Gas Sources – Industrialization , burning of fossil fuels , deforestation. CO 2 – 76 % of the total greenhouse gases. Pie chart showing the amounts of various greenhouse gases in the atmosphere .

3.   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 CO 2 from year to year Melting of ice due to global warming.

4. HOW CO 2 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 , TiO 2 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 CO 2 CO 2 is a very much T hermodynamically stable symmetrical molecule. From Gibbs–Helmholtz relationship ∆ G 0 =∆ H − T ∆ S Free energy of formation of CO 2 is -394.0 KJ/mol . Reduction of CO 2 is highly endothermic reaction. Reduction potential of CO 2 / CO 2 • − = -1.65v

6. 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 CO 2 REDUCTION 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 TiO 2 TiO 2 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 TiO2 is coupled with Cu x O, to produce mesoporous , hetero -structure composits. Band gap of Cu x O is 1.35-1.7 eV Cu x O 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

11. PICTORIAL REPRESENTATION OF SYNTHESIS OF COMPOSITES

12. SYNTHESIS OF DIFFERENT COMPOSITES Sample Amount of Cu/Cu2O (ml) Amount of TiCl4 (ml) S BET (m2·g−1) pore volume (cm 3 ·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 Further sample was characterized by XRD, TEM , FE-SEM technique XRD patterns TEM Image FE-SEM

14. CHARACTERIZATION BY PHOTOLUMINSCENSE(PL) SPECTRA PL emission spectra of pure TiO2, Cu/Cu2O nanocomposites , and the sample CT07 Pure TiO2 depicts a sharp peak around 385 nm Cu/ Cu 2 O exhibit a UV emission peak at 380 nm & visible emission peak at 520 nm

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

16. CONJUGATED POLYMERS Increases specific surface area Chemically stable. Increase charge transfer photo inducibly . Nanoscale porosity for adsorption of CO 2 molecules. Structural diversity to play as selective CO 2  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?

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

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

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

20. 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

21. CLASSIFICATION OF POROUS MATERIALS MESOPOROUS MICROPOROUS 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 .

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

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

24. 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

25. CONCLUSION This technology effectively converts the pollutant (CO 2 ) 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

26. 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