1. 1 Photocatalytic activity of SBA-15 silica-supported titania photocatalysts 王聖璋 Sheng-Chang Wang 南台科技大學 Southern Taiwan University Institute of Nanotechnology, & Department of Mechanical Engineering, Southern Taiwan University, Tainan 710, Taiwan 洪玲雅 Ling-Ya Hung 、黃肇瑞 Jow-Lay Huang 國立成功大學材料科學與工程學研究所 2007/11/17 海峽兩岸工程材料研討會 新竹 - 台灣

2. 2 南台科大 Southern Taiwan University Location Main Gate Campus Solar-cell car Nanotechnology center

3. 3 Photo catalysis TiO 2 : Solar energy conversion Catalyst Environmental pollution remediation Band gap of semiconductors

4. 4 TiO 2 Nanoparticle Broader energy band gap Recombination of electron and hole was decreased. Higher adsorption surface area

5. 5 Disadvantages and strategies Problems: Ultrafine powders will agglomerate into larger particles adverse effect on catalyst performance Separation and recovery of TiO 2 powders from wastewater are difficult limited light transmission due to scattering susceptibility to sintering Strategies Supported TiO 2 composites High active surface area UV-Visible transparent, no absorption. Stable in chemical and thermal atmospheres

6. 6 Photocatalyst supporter activated carbon clays alumina Zeolite, pore size < 1.5 nm Mesoporous SiO 2 MCM-41, CTABr, < 10 nm SBA-15, PEO20-PPO79-PEO20

7. 7 Surfactant-templated synthetic SiO 2 mesoporous P123 Well mesostructural ordering properties amphiphilic character low-cost commercial availability Biodegradability thick silica walls PEO20-PPO70-PE020 poly(ethylene oxide)-poly(propylene Oxide)- Poly(ethylene oxide) organic structure-directing agents

8. 8 TiO 2 synthesis by sol-gel method Ti(OC 3 H 7 ) 4 + 4 H 2 O  Ti(OH) 4 + 4C 3 H 7 OH The high hydrolysis reactivity of TiO 2 precursor, TTIP may cause uncontrolled local precipitation Acetic acid was added to control the hydrolysis speed

9. 9 Experimental Procedure

10. 10 SBA-15 SBA powder: 2  m (length), 400 nm (diameter) well-ordered hexagonal mesoporous silica structures, pore size = 6-7 nm Wall thickness = 5 nm FFT

11. 11 SAXS of powder SBA-15 The calcined SBA-15 powder Three resolved peaks (100), (110), (200) Well-ordered hexagonal P6mm Structure (h k l)d ( Å ) (100)95.9 (110)55.1 (200)47.8

12. 12 N 2 adsorption/ desorption isotherms of SBA-15 P/P 0 =0.68 – 0.75, Capillary condensation taking place in mesoporoes Hysteresis loop, Type IV physisorption isotherms, => mesoporous structure H1 type, uniform spheres in fairly regular array, narrow distributions of pore size. desorption adsorption Types of physisorption isotherms, IUPAC

13. 13 Pore size distribution The synthesized SBA-15 with: Uniform and narrow pore size distribution Pore size: 6~7nm 20 nm

14. 14 Pure TiO 2 XRD Particle size TEM Rutile Anatase

15. 15 XRD patterns of TiO 2 /SBA-15 Anatase : all TiO 2 /SBA-15 compositesAnatase :20%- 60% TiO 2 /SBA-15 A+R : 80% TiO 2 /SBA-15 TiO 2 grain size is decrease by supported on SBA-15 TiO 2 Anatase -> Rutile transition temp. from 700 -> 800  C

16. 16 SAXS spectra of TiO 2 /SBA-15 SBA-15 hexagonal structure still maintained after loading different amount of TiO 2 Channels of SBA-15 may contain TiO 2 particles

17. 17 N 2 adsorption/desorption isotherms of TiO 2 /SBA-15

18. 18 TiO 2 contents vs. crystal size, pore size, pore volume Crystalline size Specific area Pore size Pore volume

19. 19 Pore shape evolution SBA-15: H1 spherical shape 20-30 %TiO 2 /SBA: H1~ H2 type 60% TiO 2 /SBA: H2, ink bottle shape, some pores are seal with TiO 2 particles 80% TiO 2 /SBA: H4, plate-like or slit shaped pores, pores are serious sealed with TiO 2 particles H4 H2 H1

20. 20 TiO 2 /SBA-15 composites 20% TiO 2 /SBA-1530% TiO 2 /SBA-1560% TiO 2 /SBA-15 100 nm

21. 21 HRTEM TiO 2 nanoparticles are embedded in SBA-15 channel grain size ~ channel’s diameter d spacing=0.357nm =>Anatase TiO 2 (101) 100 nm Ti TEM cross-section image EDS DP TiO 2 SiO 2

22. 22 FTIR spectra 1090 cm -1 : Si-O-Si asymmetric stretching 470 cm -1: Si-O-Si bending mode 940 cm -1 : Si-O-Ti vibration band TiO 2 , peaks int.  Titanium incorporating into the framework of silica

23. 23 XPS 532.2 eV Si-O-Ti bonding: chemical bonding occur between TiO 2 -SiO 2 SBA-15: Si-O tetrahedral TiO 2 : Ti-O octahedral More complicated oxygen coordination states appear in TiO 2 -SBA-15 Imply that Si-O-Ti would inhibited the phase transition from of anatase to rutile TiO 2

24. 24 UV-Visible spectra 300 – 350 nm: TiO 2 particle size < 5 nm 350- 400 nm: TiO 2 particle size > 5 nm Absorption edge: blue shift calcined temp , absorption edge red shift [Ti 3+ -O - L ]*  [Ti 4+ -O 2- L ] h

25. 25 TiO 2 /SBA-15 formation mechanism SBA-15 +TTIP hydrolysis TiO 2  30 % TiO 2 < 60 % T  700  C TiO 2 > 60 % T > 800  C Amorphous TiO 2 Anatase TiO 2 Rutile TiO 2 calcined TiO 2  temp  Ink-like pore slit shaped pores spherical pore

26. 26 Standard calibration curve of Methylene Blue (MB) Beer’s Law: A ＝  b c A:absorption  :proportion constant b: light length c: concentration

27. 27 Degradation of MB Langmuir-Hinshelwood ln(C/C 0 )=kt C 0 : initial concentration of Methylene Blue k: rate constant k TiO2 : 0.004 min -1 k 30%TiO2 : 0.027 min -1 k 60%TiO2 : 0.023 min -1 30 % TiO 2 /SBA15 has the similar degradation rate with 60 %TiO 2 /SBA15 02468

28. 28 Conclusions High surface area (500 m 2 /g), high pore volume (0.55 cm 3 /g) of TiO 2 supported on SBA-15 composites have been obtain. (30 %TiO 2 /SBA-15 calcined at 700  C) Nanosized of 5 nm TiO 2 particles embedded in the channel of the mesoporous silica structures. The SBA-15 supported TiO 2 increased the formation temperature of anatase phase to rutile phase from 700  C to 800  C and inhibit the TiO 2 grain growth by the occurs of Si-O- Ti bonding. The pore shape from spherical change to plate-like or slit- shaped by increasing the TiO 2 content higher than 30 % in the mesoporous silica structure. Photocatalytic activity of SBA-15 supported TiO2 composite has 3 time increase than the commercial pure TiO2 nanopowder (P25)

29. 29 Thanks for your attention SnO nanoflower