Development of a Lower Energy Photosensitizer for Photocatalytic CO₂ Reduction: Modification of Porphyrin Dye in Hybrid Catalyst System

Abstract

A series of Zn–porphyrin dyes was prepared and anchored onto a TiO2 surface to complete a dye-sensitized photocatalyst system, Zn–porphyrin-|TiO2|-Cat, and tested as lower energy photosensitizers for photocatalytic CO2 reduction. Three major synthetic modifications were performed on the Zn–porphyrin dye to obtain a lower energy sensitization and improve the catalyst lifetime. We found that incorporating acetylene and linear hexyl groups into the Zn–porphyrin core allowed facile lower energy sensitization, and the addition of the cyanophosphonic acid as an anchoring group gave the long-term dye stability on the TiO2 surface. Under irradiation with red light of >550 nm and a light intensity of 207 mW/cm2, the hybrid ZnP CNPA catalyst showed a TONRe of ∼800 over an extended time period of 90 h. The photocatalytic activities of porphyrin hybrids differ greatly with the binding strength of the anchoring groups of dye and spectral range of the irradiated light and its intensity.

Organometallic Iridium(III) Complex Sensitized Ternary Hybrid Photocatalyst for CO2 to CO Conversion

“…[39,43,55] This interpretation is in line with our previousr eports that ah ighly durable and efficient photocatalysis is achieved only by TiO 2 immobilization of af ragile organic PS, which allows efficient charge separation and injection during photolysis. [39] Irradiation at al ongerw avelength (l > 500 nm, instead of l > 435 nm) slightly increased the TON to 407 during 150 h; this implies that the lower energy irradiation prevents photobleaching. [25,26,39] Because Brønsted acids and metal cations are known to exert ap ositive effect on Re I -a nd Mn I -based CO 2 reduction,w e furthert ested the photocatalytic performance of this hybrid system in the presence of such additives as water and trifluoroethanol (TFE;T able 4).…”

“…This is consistent with the dye concentration dependency observedi no ur previous Re I -based ternary analogues (dye/TiO 2 /Re I catalyst). [34,35,[37][38][39][40] Figure 7s hows typical plots of TON and mmol versusi rradia-tion time for the CO formation of the IrP(0.1 mmol)/TiO 2 /ReP ternary series. Under the optimum condition, the AQYs of IrP/ TiO 2 /ReP hybrids at l = 436 nm were determined to be 0.16-0.40 %( Ta ble3).…”

“…[14] The dye-sensitized photocatalysis (DSP) approachi nvolves an n-type TiO 2 semiconductor as an electron mediator anda sa scaffold that ideally links the molecular or metal components by coadsorption onto the TiO 2 surface. [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40] The DSP system rapidly consumes the reactive excited (IrPS*) or reduced (IrPSC À )s pecies with the alleviation of intermoleculari nteraction by low average coverage of the PS, consequently lessening the photodegradation of IrPS. Such coassembly of components onto as emiconductor surfacec an also allow no limitation of solvent selection based on heterogenization, with easy preparation and tunability of the DSP system.…”

Photocatalytic activity enhanced via surface hybridization

“…The researchers believe that both strong electrons coupling between the Q band of ZnP and the CB of TiO 2 and the presence of various shallow surface trapping sites (0.3~1.0 eV lower than the CB of TiO 2 ) contributed to this effective electron injection, showing the overall photophysical reaction path between ZnP and TiO 2 particles in Figure 13F. 129 TA spectroscopy was used to study the dynamics of excited carriers in p-type pentacene (0D) and n-type monolayer MoS 2 (2D) hybrid. Previously, the mechanism and time constant of the exciton decay in MoS 2 were studied ( Figure 13G).…”

Inorganic Photochemistry and Solar Energy Harvesting: Current Developments and Challenges to Solar Fuel Production

“…Won and coworkers [208] developed a series of Znporphyrin dyes to be anchored onto TiO 2 surfaces to complete a dye-sensitized photocatalyst system based on Zn-porphyrin-|TiO 2 |-Re(Cl)(CO) 3 (ByPh). These dyes were tested as low-energy photosensitizers for photocatalytic CO 2 reduction.…”