Nanostructured TiO2
(May 1998 - July 2001)
A novel preparation procedure for nanostructured TiO2 was developed. The synthesis technique, based on modified sol-gel method involves the controlled precipitation of amorphous gel material, followed by careful crystallization under hydrothermal conditions [1,2,9,11,12]. Using this technique, TiO2 with well-defined phase structure (i.e., anatase or rutile), controlled crystal and aggregate size (i.e., 2-25 nm crystals, 100-1000 nm aggregates) and shape (i.e., spheres, rods and plates) and crystallinity were successfully prepared and studied. The ability to prepare nanometer sized TiO2 and engineer its size and structure enable us to elucidate the role of electronic and ensemble effects in the activity of these catalysts for catalytic and photocatalytic reactions [5]. The reactivity of the nanometer sized TiO2 was investigated for gas phase, photocatalytic oxidation of volatile organic compounds (VOC) including alcohols (i.e., ethanol [10]), aromatics (i.e., toluene [3,6]) and halogenated compounds (i.e., trichloroethylene [1,2,7,8], cis- and trans-dichloroethylene [11,13,15], vinylidene chloride and tetrachloroethylene). Both fundamental and application issues were addressed in the study. The nanostructured TiO2 prepared by the new technique displays order of magnitude improvement in photocatalytic mineralization of airborne VOC compared to the commercial TiO2 (P25, Degussa).
The complexity of the problem necessitates the participation of several researchers and research groups:
Dr. King Lun Yeung (Chemical Engineering, HKUST) developed the novel synthesis method for nanostructured TiO2. Responsible for the catalyst characterization and activity evaluation for halogenated compounds. Implemented in situ infrared analysis of gas-phase, photocatalytic oxidation reactions. Managed and maintained the international, interdisciplinary collaboration.
Prof. Po-Lock Yue (Chemical Engineering, HKUST) contributes his expertise in the photocatalysis and in particular photoreactor analysis.
Dr Chak Keung Chan and Dr. John F. Porter (Chemical Engineering, HKUST) lend their support during the inception of the research and had provided valuable guidance in the use of micro-Raman for TiO2 characterization.
Prof. Javier Soria (Instituto de Catalisis y Petroleoquimica, Spain) is a well-known expert in photocatalysis and his team's electron paramagnetic resonance (EPR) study is key in elucidating the roles of electronic and structure on the catalytic performance of the nanostructured TiO2. His team members include: Dr. Juan M. Coronado, Dr. A. Javier Maira, Dr. Jose Carlos Conesa and Dr. Vicenzo Augugliaro who had actively participated in the collaboration.
Prof. Kuei-jung Chao (National Tsinghua University, Taiwan) has conducted the synchrotron X-ray diffraction (XRD), X-ray absorption near edge spectroscopy (XANES) and (EXAFS) at the Synchrotron Radiation Research Center (SRRC), Taiwan. The structural information contributes towards a better understanding of the role of structure and defects on the overall performance of the TiO2.
Dr. Asterios Gavriilidis (University College, London, UK) is involved in the application of the nanostructured TiO2 as support material for Au/TiO2 catalyst for low temperature (i.e., room temperature) oxidation of carbon monoxide to carbon dioxide. The use of nanometer sized TiO2 leads to a reduction in gold loading (i.e., from 2 wt.% to 0.1 wt.%) without compromising the catalyst performance resulting in a significant cost saving.
1. HKUST6026/98P A cascade solar powered photocatalytic reactor for wastewater treatment.
STATUS: On-going (September 1998 - present)
SUMMARY: The objective is to develop a low-cost alternative technology for wastewater remediation to address environmental problem in Southern China and Asia-Pacific regions. The research will involve the design and construction of a solar powered photo-reactor for complete degradation organic pollutants in wastewater to CO2 and water.
CONTRIBUTIONS: As co-investigator, I had provided synthesis technology for catalyst film coating onto support surfaces.
2. HKUST6247/00P A novel photocatalytic system with aerogel matrix of nanometer-sized catalyst particles for the removal of volatile organic compounds (VOCs).
STATUS: On-going (September 2000 - present)
SUMMARY: The objective is to develop a self-supporting, low density, self-supporting matrix of TiO2 aerogel with nanometer-sized crystals for application in photocatalytic abatement of airborne pollutants.
CONTRIBUTIONS: As co-investigator, I had provided the technology for nanostructured TiO2 with superior photocatalytic activity for oxidation and mineralization of volatile organic pollutants.
3. Institute of Nano Science and Technology (INST) Nanostructured TiO2 environmental catalysts.
PRINCIPAL INVESTIGATOR: King Lun Yeung
STATUS: Completed
SUMMARY: The objective of the project is to determine the role of electronic and ensemble effects on the catalytic properties of nanostructured TiO2 using photo-oxidation of halogenated organic compounds as probe reaction.
Students: (4 post-doctoral researchers, 5 undergraduate students)
· Dr. A. Javier Maira (European Postdoctoral Fellow, May, 1998 - November, 1999)
· Ms. Chi Yan Lee (UG student (CENG 298), May-August, 1999; part-time Jr. R.A., September-December, 1999)
· Ms. Wai Ngar Lau (UG student (CENG 398), May-August, 2000; part-time Jr. R.A., September-December, 2000)
· Ms. Eppie Hung (part-time Jr. R.A., August-December, 2000)
· Ms. Jennifer Stolz (UG Exchange student from Germany, August, 2000-May, 2001)
· Dr. Sze-Tai Yau (Research Associate, January, 2001 - August, 2002)
· Dr. Xinyong Li (Research Associate, July, 2001- June, 2002)
· Mr. Anderson H. C. Shum (UG Exchange student from Princeton University, June - September, 2002)
· Dr. N. Yao (Research Associate, October, 2002 - present)
Publications and Presentations: (9 peer-reviewed journal manuscripts, 13 presentations)
1. A.J. Maira, K.L. Yeung, C.Y. Lee, P.L. Yue, C.K. Chan, "Size effects in gas-phase photo-oxidation of trichloroethylene using nanometer-sized TiO2 catalysts," J. Catal., 192 (2000) 185-196. PDF
2. A.J. Maira, K.L. Yeung, C.K. Chan, J.F. Porter and P.L. Yue, "Catalyst Preparation and Reactor Design for Gas-Phase Photocatalytic Oxidation of Trichloroethylene (TCE) Pollutant," Stud. In Surf. Sci. and Catal., 130 (2000) 1949-1954.
3. A.J. Maira, K.L. Yeung, J. Soria, J.M. Coronado, C. Belver, C.Y. Lee and Augugliaro, V., "Gas-phase photo-oxidation of toluene using nanometer-size TiO2 catalysts," Appl. Catal. B Environmental, 29 (2001) 327-336.
4. S.J. Lee, A. Gavriilidis , Q.A. Pankhurst, A. Kyek, F. E. Wagner, P.C.L. Wong and K.L. Yeung, "Effect of Drying Conditions of Au-Mn Co-precipitates for Low Temperature CO Oxidation," J. Catal., 200 (2001) 298-308. PDF
5. J.M. Coronado, A.J. Maira, J.C. Conesa, K.L. Yeung, V. Augugliaro and J. Soria, "EPR study of the surface characteristics of nano-structured TiO2 under UV-irradiation," Langmuir, 17 (2001) 5368-5374. PDF
6. A.J. Maira, J.M. Coronado, V. Augugliaro, K.L. Yeung, J.C. Conesa and J. Soria, "FTIR study of the performance of nanostructured TiO2 particles for the photocatalytic oxidation of gaseous toluene," J. Catal., 202 (2001) 413-420. PDF
7. K.L. Yeung, A.J. Maira, J. Stolz, E.W.C. Hung, N.K.C. Ho, A.-C. Wei, J. Soria, K.-J. Chao and P.-L. Yue, "Ensemble effects in nanostructured TiO2 used in the gas phase photo-oxidation of trichloroethylene," J. Phys. Chem. B, 45. 106 (2002) 4608-4616. PDF
8. J. Maira, W.N. Lau, C. Y. Lee, P. L. Yue, C. K. Chan and K. L. Yeung, “Performance of a Membrane-Catalyst for Photocatalytic Oxidation of Volatile Organic Compounds,” Chem. Eng. Sci.,58 (2003) 959 - 962. PDF
9. K.L. Yeung , S.T. Yau, A.J. Maira, J.M. Coronado, J. Soria and P.L. Yue, “The influence of surface properties on the photocatalytic activity of nanostructured TiO2,” J. Catal., 219 (2003) 107-116. PDF
Conferences and Invited Talks:
1. A.J. Maira, K.L. Yeung, C.K. Chan, J.F. Porter and P.L. Yue, "Preparation of Nanostructured TiO2 Photocatalysts," Asia Pacific Conference on Reaction Engineering at Hong Kong, China, June 13-16 1999.
2. S.-J. Lee, A. Gavriilidis , Q.A. Pankhurst, A. Kyek, F. E. Wagner and K.L. Yeung, "Effect of Preparation Conditions of Au-Mn Co-precipitates for Low Temperature CO Oxidation," Asia Pacific Conference on Reaction Engineering at Hong Kong, China, June 13-16 1999.
3. A.J. Maira, C.Y. Lee, K.L. Yeung, C.K. Chan and P.L. Yue "Performance of Nanostructured TiO2 Photocatalysts for Gas-phase Photocatalytic Oxidation of Ethanol and TCE," 2nd International Conference on Oxidation Technologies for Water and Wastewater Treatment at Clausthal-Zellerfeld, Germany, May 28-31, 2000.
4. A.J. Maira, K.L. Yeung, C.Y. Lee, C.K. Chan and P.L. Yue, "Preparation and Characterization of Nanostructured TiO2 Photocatalysts," AOTS-6 and TiO2-5 at Ontario, Canada, June 25-30, 2000.
5. A.J. Maira, K.L. Yeung, C.K. Chan, J.F. Porter and P.L. Yue, "Catalyst Preparation and Reactor Design for Gas-Phase Photocatalytic Oxidation of Trichloroethylene (TCE) Pollutant," 12th International Congress on Catalysis at Granada, Spain, July 9-14, 2000.
6. A.J. Maira, C.Y. Lee, K.L. Yeung, C.K. Chan and P.L. Yue, "Nanostructured TiO2 for photocatalytic oxidation of VOC pollutants," AIChE 2000 at Los Angeles, CA, November 12-17, 2000.
7. K.L. Yeung, "Preparation of nanostructured TiO2 catalyst for gas phase photocatalytic oxidation of VOC pollutants," The First AEARU Environmental Workshop at Hong Kong, China, January 8-10, 2001.
8. K.L. Yeung, J. Stolz, S.T. Yau and P.L. Yue, "In-situ FTIR investigation of photocatalytic oxidations of volatile chlorinated C2 compounds on nanostructured TiO2," TiO2-6, Niagara Falls, Ontario, Canada, June 25-29, 2001.
9. A.J. Maira, J. M. Coronado, J. Soria, J.C. Conesa, V. Augugliaro and K. L. Yeung, "Toluene photocatalytic degradation on TiO2 nanoparticles: Activity and FTIR studies," 5th European Congress on Catalysis, Limerick, Ireland, September 2-7, 2001.
10. S.T. Yau and K.L. Yeung, “Photoreactor design and evaluation for gas phase photocatalytic oxidation of volatile organic compounds,” ISCRE-17 at Hong Kong, August 25-28, 2002.
11. K.L. Yeung, S.T. Yau and P.L. Yue, "Influence of the surface properties of nanostructured TiO2 on the photo-oxidation of airborne trichloroethylene," TiO2-7 at Toronto, November 17-21, 2002.
12. K.L. Yeung, A.J. Maira, W.N. Lau and P.L. Yue, "Performance of membrane-catalyst for photo-oxidation of volatile organic compounds," TiO2-7 at Toronto, November 17-21, 2002.
13. S. Cao, K.L Yeung and P.L. Yue, "Monolithic silica-titania aerogels by modified sol-gel method," ICC-13 at Paris, France, July 11-16, 2004.
