Details

Autor(en) / Beteiligte

• Choi, Sunghan
• Choe, Min Su
• Lee, Daehan
• Kim, Soohwan
• Wee, Kyung-Ryang
• Shin, Jae Yoon
• Son, Ho-Jin

Titel

Efficient Photosensitization of π‑Extended Oligomeric Porphyrin Pigments through TiO2‑Mediated Outer-Sphere Electron Transfer in Photochemical CO2 Reduction Systems

Ist Teil von

• ACS applied energy materials, 2024-05, Vol.7 (9), p.3602-3617

Ort / Verlag

American Chemical Society

Erscheinungsjahr

2024

Link zum Volltext

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• This study describes an effective approach for addressing the challenges associated with low-lying excited states in π-extended porphyrin oligomeric dyes ([ZnP]-[ZnP] (D-ZnP) and [ZnP]-[ZnP]-[ZnP] (T-ZnP), where ZnP = Zn­(II)-porphyrin unit), which create an energy barrier in the electron transfer (ET) process from the oligomeric dye to the catalytic center and hinder the maximal utilization of the superb visible-light-harvesting ability of oligomeric porphyrin arrays in dye-sensitized photocatalysis (DSPC). The outer-sphere ET from the porphyrin array dyes to TiO2, initiated by a shallow trapping site with a low-energy level within the bulk TiO2 semiconductor (positioned 0.3–1.0 eV below the conduction band (CB) of TiO2), efficiently mitigated the endergonic ET process from the porphyrin array dye to the catalytic center. In the photolysis experiments of the TiO2-mediated hybrid system (dye + TiO2/Re­(I) catalyst), the D-ZnP and T-ZnP-sensitized photocatalytic systems exhibited superior CO2 conversion activities (turnover number (TON)CO = 1939 for D-ZnP and 1757 for T-ZnP) compared with the monomeric Zn­(II) porphyrin dye (TONCO = 837 for M-ZnP). This enhancement is attributed to the alleviation of the endothermic ET process achieved through TiO2 mediation and the excellent light-harvesting capacity facilitated by π-extension. In contrast, the photolysis results for the mixed homogeneous system (dye + Re­(I) catalyst) indicated relatively lower conversion performances of the D/T-ZnP-sensitized homogeneous systems due to the uphill photoinduced ET between components caused by the low-lying lowest unoccupied molecular orbital (LUMO) levels of porphyrin array dyes (E red1 1/2 = −1.30, −1.18, and −1.14 V (vs SCE) for M-ZnP, D-ZnP, and T-ZnP, respectively). The proposed strategy provides a useful tool for achieving efficient photosensitization of long π-conjugated dye arrays in various photocatalytic systems.