Visible Light-Driven Dye-Sensitized Photocatalytic Hydrogen Production by Porphyrin and its Cyclic Dimer and Trimer: Effect of Multi-Pyridyl-Anchoring Groups on Photocatalytic Activity and Stability

Abstract

The monomer, dimer, and trimer of 5,15-diphenyl-10,20di(pyridin-4-yl)porphyrin are used to investigate the multi-anchoring eff ect on TiO2 for visible light-driven photocatalytic hydrogen production in a water medium. Further, the porphyrin trimer is prepared and analyzed by nuclear magnetic resonance (NMR) spectroscopy, absorption spectroscopy, electrochemical voltammetry, fast atom bombardment (FAB) mass spectroscopy, and density functional theory (DFT) computation. The results of this study indicate that the peak intensities of the absorption spectra increase as the number of porphyrin units increases, while changes could be barely observed in the highest occupied molecular orbital (HOMO)−lowest unoccupied molecular orbital (LUMO) gaps. The porphyrin dimer in a 1 wt % Pt-loaded TiO2 powder photocatalyst system exhibited optimal hydrogen production performance in a stable state over a period of 80 h and at a superior rate of 1023 mol•g −1 •h −1. Further, the stability of the photocatalytic system was systematically investigated using films containing dyes on 1 wt % Pt-loaded TiO2/FTO. For a film containing the dimer, almost no change was observed in the hydrogen-bond coordination mode of the dimer and the photocurrent during the photocatalytic reaction. However, the photocurrents of the monomer and trimer were altered during visible light irradiation without altering the coordination mode, indicating that the arrangements and orientations of the porphyrins on TiO2 surfaces were altered. These results indicate that the presence of multiple anchoring groups enhance the stability of the photocatalytic system and the rate of hydrogen production.

Photocatalytic H2 Production from Water by Metal‐free Dye‐sensitized TiO2 Semiconductors: The Role and Development Process of Organic Sensitizers

“…However, no obvious change in the absorption band of Dimer‐2 was observed. The results above indicated that Dimer‐2 had the best binding mode with TiO 2 , therefore benefiting its photocatalytic performance under long‐term irradiation [83] …”

“…The results above indicated that Dimer-2 had the best binding mode with TiO 2 , therefore benefiting its photocatalytic performance under long-term irradiation. [83] Yuan Sun et al creatively combined commercial porphyrin derivative dye Chl and indoline-rhodanine dye Ind together by ester bond to form the new dual-moieties dyad dye (donated as Dyad) ( Figure 41 and Table 1, No. 117-119).…”

“…A) Structures of dyes Monomer-1, Dimer-2, and Trimer-3, and B) corresponding H 2 evolution plots. Reproduced from Ref [83]…”

A triptych photocatalyst based on the Co-Integration of Ag nanoparticles and carbo-benzene dye into a TiO2 thin film

“…Therefore, various strategies have been explored to improve the WS efficiency under solar illumination. The band gap can be narrowed and light absorption extended to longer wavelengths by doping with non-metal atoms [21,22], with organic dyes [23] such as ruthenium complexes [24], porphyrins [25], or graphene oxide [26][27][28][29]. Another strategy to improve the PC efficiency relies on the use of hybrid metal nanoparticles/semiconductor nanostructures [30][31][32][33][34][35][36][37][38][39][40][41][42][43][44], in order to reduce the electron-hole recombination and/or to harvest the visible light owing to plasmonic enhanced optical absorption [29,30,45].…”

Photosensitive Hybrid Nanostructured Materials: The Big Challenges for Sunlight Capture

“…The effect of the anchoring mode of porphyrin derivatives was evaluated by means of surface silanization by APTES (3-aminopropyl triethoxysilane), allowing an amide covalent grafting on TiO 2 and SiO 2 nanoparticles [34], or surface modification by maleic anhydride of a Fe 3 O 4 @SiO 2 @TiO 2 magnetic composite, achieving in both cases stable anchoring and photocatalytic activity [35]. Moreover, using a dimer or trimer of porphyrin with a pyridyl anchoring group, which formed H-bonds on the TiO 2 surface, enhanced both hydrogen generation rate under visible light and stability [36]. A few applications of specifically synthesized metal-free phthalocyanines have also been reported.…”