Metal-oxides and Carbon Nano -Materials for Energy Applications

1. Metal-oxides and Carbon Nano-Materials for Energy Applications Dr S K Samdarshi Department of Energy Tezpur University, Tezpur E-mail: drsksamdarshi@rediffmail.com II ALL THAT EXISTS WAS BORN FROM THE SUN II Brhad-devata I:61

2. Polytypism in Metal Oxides: Advantage Visible Photocatalysis Dr S K Samdarshi Centre For Energy Engineering Central University of Jharkhand University, Ranchi 835205 Jharkhand E-mail: drsksamdarshi@rediffmail.com

3. Contents • Energy & Materials • Novel Energy Materials • Photo-catalysis • Novel Applications • Conclusion

4. A. Energy and Materials

5. Energy Application Materials • Energy utilization, conversion, and storage • Macroscale nanoscale • Structural and functional properties of active materials and their interfaces at nanoscale. • Applications: • Batteries, Supercapacitors, Fuel Cells: Electrodes, electrolytes • Photocatalysis, and Photovoltaics: Nanoparticles, nanostructured systems, Films • Other novel apps. Nanogenerators, Bio-energy ?

6. B. Novel Energy Materials

7. Materials and Dimensions Material with novel structural and functional properties • 0-D structures • Metal oxide nanoparticles(<5nm ?) • Fullerene • 1-D structures • Metal oxide nanotubes/nanorods • Carbon nanotubes/nanorods • Carbon microtubes • 2-D structures • Graphene • 3-D structures ?

8. C. Photo-catalysis

9. Photocatalytic Materials • Direct Photocatalytic Applications • Environmental-Detoxification, Disinfection • Energy - Solar Hydrogen Production • Environmental + energy - CO2 valorization • Indirect/Alternative Applications: • Photo-electrochemical Cell • Solar Photovoltaic Application- OPV, and DSSC • Spin-offs • Photonics/optoelectronics • Spintronics • Piezoelectric nanogenerators

10. Industrial Applications Paints with self-cleaning characteristics Ordnance factory effluent treatment Dyeing, dairy, tanning industries Pharmaceuticals industries, Nursing homes Cosmetics Industries Optoelectronics Sensors; Nanogenerators Spintronic devices; High density memory chips

11. Fujishima and Honda, Nature, 1972 Photocatalysis i) semiconductor photocatalyst ii) initiator iii) in the presence of light

12. Photocatalysis: Basic Mechanism Photon Electron Hole 3 Conduction band Photocatalyst Eg Valance band 2 O2 1 Reduction O2- H2O Oxidation .OH + H+ • Applications • Solar detoxification (Air, Water, Soil) • Solar disinfection (Air, Water, Soil) • Solar hydrogen production (Water) • Solar Carbon valorization(Air, Water)

13. Advantages of Titania: Photostable, cheap & reusable, chemically & biologically inert, high activity at ambient temperature. Photocatalyst Materials

14. Direct Photocatalytic Application • Problems and Issues • Photon harvesting/Absorption (Red-shift) • Carrier generation and separation • Carrier transport/migration • Utilization / photocatalytic activity • Reusability

15. Anatase Rutile Structure and Band gap of TiO2 Brookite

16. Active Phase: Anatase Problems of titania • Low absorption wavelength (< 380 nm) • Recombination of charge carriers(Rutile) • Low surface area

17. Red-shift Pristine Anatase TiO2 Options to red-shift the absorption wavelength • Doping (anions/cations) • Co-doping • Metal oxide Complexes • Sensitization (Dye/Plasmonic Resonance)

18. Options available to reduce recombination TiO2 TiO2 TiO2 TiO2 MOx Y Eg Eg Eg Eg Eg • Mixed oxide • complex Sensitization • Mixed phase complex • Mixed oxide complex • Multi-phasicMOx with homojunction • Sensitization (with Noble metals/dyes/graphene)

19. Options to increase specific surface Area • Nanoscale synthesis • Templating (Surfactant/Bio) Templating

20. Research Activities • Silver sensitized V doped TitaniaNanoparticles • Vanadium doped TitaniaNanoparticles • Mixed Phase(MF) TitaniaNanoparticles • Nitrogen doped TitaniaNanoparticles • Bio-templated Hierarchical superstructures • Metastable zinc oxide based systems • Black titania systems

21. Synthesis Metal Salt + Oxidant Organometallic + M-OH Organometallics Autoclave + Calcination Hydrolysis + Calcination Heat Metal oxide Metal oxide Metal oxide Hydrothermal Solution Combustion Sol-gel method Sol-gel method(Hydrolytic/Non-hydrolytic) Hydrothermal method Solution combustion method

22. A. Ag/TiV oxide B. TiV oxide UV-DRS TEM SAED Pattern HRTEM

23. Detoxification MB Phenol A. Methylene Blue B. Phenol Solar Energy Materials and Solar Cells, Elsevier, 94, 2379-2385,2010

24. Disinfection Ag/TiV oxide (30 min) Ag/TiV oxide (60 min) TiV oxide (30 min) TiV oxide (60 min)

25. Disinfection of E-Coli Bacteria Colloids and Surfaces B: Biointerfaces (Elsevier), 86, 7–13.

26. Microbicidal Photonic Efficiency Photonic efficiency V=volume (l); ∆C= change in concentration (M); J = flux of photons (Einstein/m2/sec); A= illuminated area (m2); ∆t=change in time (sec). ∆N – Change in CFU count, Ap = effective plating area; NA =Avogadro’s constant Why DP25 shows visible activity ?

28. XRD results Spurr’s Equation Scherrer Formula

29. UV-Vis-DRS spectra

30. Activity dependence on A/R ratio and irradiation spectrum Visible UV Variation in rate constant in degradation of Phenol with increase in rutile content under UV and Visible irradiation

31. Variation with A/R phase ratio and Crystallite size Jung et al, Catalysis Communications (2004) Su et al, Journal of Physical Chemistry C, 2011

32. Photocatalytic model for Biphasic Titania a. b. c. hν (λ> 380 nm) hν (λ380 nm) Barrier Potential Barrier Potential Barrier Potential e e e e e e 3.0 eV 3.0 eV 3.2 eV 3.2 eV 3.0 eV 3.2 eV h h h h h h Rutile Sink model (Beakley, UNM)) Rutile Antenna model (Gray, NWUniv)

33. Interface model for Biphasic TiO2 a. b. c. hν (λ> 380 nm) hν (λ380 nm) Barrier Potential Barrier Potential Barrier Potential e e e e e e 3.0 eV 3.0 eV 3.2 eV 3.2 eV 3.0 eV 3.2 eV h h h h h h

34. Biphasic/mixedphase charge separation Size dependence of the electronic structure of several oxide nanocomposite systems. Valence and conduction bands are represented by the corresponding top and bottom edges, respectively. Blue/red arrows describe UV/visible light induced charge transfer processes. Kubacka et al, Chemical Reviews, 2012

35. Is it possible to further enhance the activity ? Increase the specific surface area Bio-inspired systems

36. Bio-templating using Cotton(? ) Cellulose (C6H10O5)n Chemical composition of cotton fiber Cellulose = 95% Protein = 1.3% Ash = 1.2% Wax = 0.6% Sugar = 0.3% Organic acids = 0.8% Other chemical compounds = 0.8%

37. Metal chlorides + Ether/Alcohol(R-alkyl group) [Ti]-Cl + ROH [Ti]-OR + HCl [Ti]-Cl + ROR [Ti]-OR + RCl [Ti]-Cl + [Ti]-OR  [Ti]-O- [Ti] + R-Cl

38. NH-TiO2 -XRD and BET X-ray powder diffractograms of the calcined materials. N2 adsorption–desorption isotherms at -196oC of the calcined materials derived from cotton wool (top) and corresponding pore size distributions (bottom). Boury et al, New Journal of Chemistry, RSC, 2012

39. Bio-template based hierarchical superstructure

40. XRD, BET, Raman Analysis

41. BET, XRD, TEM Analysis

42. UV-DRS and PL Analysis

43. Photo-catalytic Kinetics(UV)

44. Bio-templated Hierarchical Superstructure High specific surface area and photon harvesting features are probably responsible for this( Boury and Samdarshi, Eur J of In Chem, 2013) Mixed phase in other semiconductor systems?

45. ZnO phases • Wurtzite • Zincblende Rocksalt Mixed phase ?

46. ZnOnaostructures Nanohelix Nanopyramid Nanotetrapod All Wurtizite ? Lazzarini et al ACS Nano, 2009 Lu et al, Adv Func Mat, 2008 Gao et al, Science, 2005

47. ZnOnaostructures St - Stearate Yang et al, JACS, 2010 All Wurtizite ?

48. ZnO and Co doped ZnO- Mixed Phase ? Co doped ZnO – Wurtzite (SG: P63MC) (JCPDS) Hydrothermal Synthesis

49. ZnO/Co-ZnO:Visible Kinetics PL Visible - MB Visible - Phenol

50. ZnO phases • Zincblende • Wurtzite Mixed Zincblende and Wurtzite phase in Co doped ZnO