| Author: | Kwok, Yan Yi |
| Title: | Rational design and synthesis of robust functional photosensitizers for light-driven hydrogen production |
| Advisors: | Ho, C. L. (ABCT) |
| Degree: | Ph.D. |
| Year: | 2023 |
| Subject: | Photosensitizing compounds Hydrogen as fuel Organic compounds -- Synthesis Hong Kong Polytechnic University -- Dissertations |
| Department: | Department of Applied Biology and Chemical Technology |
| Pages: | 455 pages : color illustrations |
| Language: | English |
| Abstract: | This work focuses on developing novel robust triphenylamine-based starburst and fluorenone-based organic dyes with D-π-A structures, 9,9'-dihxylfluorene-based D-D-(π-A)2 di-anchoring dyes and fluorene-based simple molecules with π-extended structure at the C-9 position of fluorene, and porphyrin-based photosensitizers with various combinations of metal centres, electron-donating and anchoring moieties for panchromatic visible light absorption and co-sensitization. A total of 47 dyes were designed, synthesized and characterized photophysically and electrochemically. In the second chapter, a series of robust donor-donor-π-acceptor (D-D-π-A) triphenylamine-based starburst organic dyes with various electron-donating moieties and thiophene-based π-linkers were synthesized and characterized. Notably, P4 attained an active and robust H₂ generation system with the ON of up to 24900 in 252 hours with 1560 µmol (37.6 mL) hydrogen produced. The initial turnover frequency (TOFi) was 1130 h⁻¹, the initial activity (activityi) was 710 mmol g⁻¹h⁻¹, and the initial apparent quantum yield (AQYi) was 12.1%, under visible light irradiation from water, which is one of the best performed metal-free organic photosensitizers that have been reported. In the third chapter, A series of di-branched di-anchoring dyes D-D(-π-A)2 (D1-D6, D6M, D45), therefore, with 9,9'-dihxylfluorene as the common electron donor and different electron-rich moieties (phenothiazine, carbazole, triphenylamine, diphenylamine, and 9-phenylcarbazole) as the bridging donors, thiophene and methine as the electron transfer π-bridge, and cyanoarylic acid as the electron acceptor and anchoring group were synthesized and coupled onto TiO₂. F1-F10 were also synthesized to find out the effect of π-expansion of fluorene at C-9 position by benzene/ triphenylamine/xanthene/fluorene in mono-/di-anchoring systems. Among the donor moieties conjugated with 9,9'-dihexylfluorene at their N atom (except triphenylamine), diphenylamine conjugated dye (D6) had the best performance, generating 1090 µmol (26.3 mL) hydrogen with up to 17400 of turnover number (TON) in 126 hours. The initial turnover frequency (TOFi) was 808 h⁻¹, the initial activity (activityi) was 505 mmol g⁻¹h⁻¹, and the initial apparent quantum yield (AQYi) was 8.65%, under visible light irradiation in water, which is highly comparable to the reported dianchoring organic dyes. The most remarkable one would be F4, yielding 3520 µmol (84.9 mL) hydrogen produced over 257 hours under blue light with TON of 56300, TOFi of 1860 h⁻¹, Activityi of 1160000 and AQYi% of 19.9, achieving the best performance among all dyes in this chapter. The stability of F4 and D6 were also remarkable as they remained active in generating hydrogen over 257 and 126 hours under blue light and 257 and 189 hours under green light, respectively. The D-D(-π-A)₂ structure and π-extended fluorene could potentially boost the stability and robustness and suppress the charge recombination of the organic photosensitizers in the photocatalytic hydrogen evolution system. In the fourth chapter, the PHE system with porphyrin-based PoTA3 had the highest and most remarkable initial photocatalytic activity, with the initial apparent quantum yield % (AQYi%) of 8.3% and the initial hydrogen production activity (activityi) of 485 mmol g⁻¹ h⁻¹ under blue light irradiation, followed by PoTA1 (AQYi% = 6.5% and activityi = 378 mmol g⁻¹ h⁻¹) and PoTA2 (AQYi% = 4.4% and activityi = 258 mmol g⁻¹ h⁻¹). Both the PoTA1 and PoTA3 had distinctive performances under white light irradiation, with the AQYi% = 5.5% and 6.8% respectively, and surpass that of the classical YD2-0-C8 (AQYi% = 4.07%). |
| Rights: | All rights reserved |
| Access: | open access |
Copyright Undertaking
As a bona fide Library user, I declare that:
- I will abide by the rules and legal ordinances governing copyright regarding the use of the Database.
- I will use the Database for the purpose of my research or private study only and not for circulation or further reproduction or any other purpose.
- I agree to indemnify and hold the University harmless from and against any loss, damage, cost, liability or expenses arising from copyright infringement or unauthorized usage.
By downloading any item(s) listed above, you acknowledge that you have read and understood the copyright undertaking as stated above, and agree to be bound by all of its terms.
Please use this identifier to cite or link to this item:
https://theses.lib.polyu.edu.hk/handle/200/13560