Mechanistic Insights into the Photocatalytic Hydrogen Production of Y5 and Y6 Nanoparticles

Utilization of solarenergy in organic semiconductorsrelies oncomplicated photophysical processes due to the strong electron-holeinteractions. To gain a better understanding of these processes andtheir effect on the photocatalytic performance of non-fullerene acceptors(NFAs) within nanoparticles (NPs), we compared the excited-state dynamicsand photocatalytic hydrogen production activity of two NFA-based NPs,Y5 and Y6. Our results show that under LED light irradiation, Y5 NPsexhibit 14 times better hydrogen production activity than Y6 NPs.The hydrogen production activity was also evaluated under Xenon lightirradiation (AM1.5G, 100 mW & BULL;cm(-2)) for Y5 NPs,yielding 410 mmol/g after 24 h. Time-resolved spectroscopy experimentsrevealed a longer triplet lifetime for Y5 compared to Y6 NPs, andthe lifetime was reduced upon addition of the electron donor ascorbate.This suggests the involvement of the triplet state in reductive quenchingand better hydrogen evolution reaction performance for Y5 NPs. Thegood agreement between fluorescence and triplet lifetimes observedfor Y5 NPs was attributed to reverse intersystem crossing, which repopulatesthe excited singlet state through thermally activated delayed fluorescence(TADF). The absence of TADF in Y6 NPs could limit its efficiency forhydrogen evolution reaction, in addition to the intrinsically shortertriplet lifetime and reduction potential difference, making it animportant factor to consider in Y series-based NPs

Preparation, characterization, evaluation and mechanistic study of organic polymer nano-photocatalysts for solar fuel production

Production of renewable fuels from solar energy and abundant resourses, such as water and carbon dioxide, via photocatalytic reactions is seen as a promising strategy to adequately address the climate challenge. Photocatalytic systems based on organic polymer nanoparticles (PNPs) are seen as one avenue to transform solar energy into hydrogen and other solar fuels. Semiconducting PNPs are light-harvesting materials with exceptional optical properties, photostability, low cost and low cytotoxity, whose performance surpasses conventional organic dyes and inorganic semiconductors. This review introduces the optimization strategies for the preparation methods of PNP via cocatalyst loading and morphology tuning. We present an analysis on how the preparative methods will impact the physico-chemical properties of these materials, and thus the catalytic activity. A list of experimental techniques is presented for characterization of the physico-chemical properties (optical, morphological, electrochemical and catalytic properties) of PNPs. We provide detailed analysis of PNP photochemistry during photocatalysis with focus on the mechanistic understanding of processes of internal charge generation and transport to the catalyst. This tutorial review provides the reader with the guidelines on current strategies used to optimize PNP performance highlighting the future directions of polymer nano-photocatalysts development