Demonstrating Donor–Acceptor Covalent Conjugate of Polythiophene and Perylene Diimide as an All-Organic Photocatalyst for Enhanced Light-Driven H₂O₂ Production

Photocatalytic production of hydrogen peroxide (H₂O₂) is being extensively explored as a cleaner route to one of the most consumed oxidants. In this context, precisely designed organic semiconductor polymers have only recently been recognized as promising photocatalysts. Contributing to this emerging area, herein, we present the potential of a donor-acceptor (D-A) covalent conjugate of polythiophene (PTh) and perylene diimide (PDI) as an all-organic photocatalyst for the artificial photosynthesis of H₂O₂. Such D-A conjugates of organic semiconducting polymers (OSPs) are termed double-cable polymers (DCPs). The DCP employed in this study, PTh-PDI-DCP, is derived from the covalent conjugation of the electron donor polythiophene and the electron acceptor perylene diimide (PDI). Compared to the individual components poly-3-hexylthiophene (P3HT), PDI, and their physical hybrid (P3HT-PDI-PH), PTh-PDI-DCP exhibited superior fluorescence and (photo)electrochemical (PEC) characteristics. All the photocatalysts were supported on a porous polyvinylidene difluoride (PVDF) membrane for their convenient application as photocatalysts over multiple cycles. A comparison of the photocatalytic H₂O₂ production rates averaged over 7 photocatalytic cycles suggests that the PTh-PDI-DCP photocatalyst is 1.56, 2.43, and 1.35 times more active than the P3HT, PDI, and P3HT-PDI-PH, respectively. Furthermore, the H₂O₂ production using the DCP photocatalyst involves significant contributions of 2e^- one-step oxygen reduction reaction (ORR) and water oxidation reaction (WOR). Overall, this work reveals for the first time the photocatalyst potential of all-organic DCPs for the photocatalytic production of H₂O₂.