Regulating Exciton Behavior of Porphyrins via Side‐Chain Engineering for Efficient Photocatalytic Hydrogen Evolution

Abstract The short diffusion length ( L _D ) and high binding energy ( E _b ) of excitons for organic photocatalysts lead to intense geminate recombination, which is the main issue limiting the rate of photocatalytic hydrogen evolution reaction (HER). Herein, oligo(ethylene glycol) (OEG) chains are attached onto the porphyrin to develop three photocatalysts, ZnTPP‐1O, ZnTPP‐3O, and ZnTPP‐5O, and regulate exciton diffusion and dissociation to enhance the photocatalytic HER rate. Among them, ZnTPP‐3O presents moderate dipole moment, the highest crystallinity, and the longest exciton lifetime, which contributes to the lowest E _b of 0.27 eV and prolonged L _D , compared to ZnTPP‐1O and ZnTPP‐5O. Therefore, the photocatalyst based on ZnTPP‐3O nanoparticles (NPs) achieves a superior HER rate of 21.1 mmol g ⁻¹ h ⁻¹ under the illumination of AM 1.5G (100 mW cm ⁻² ) simulated sunlight, which is the highest value for single‐component porphyrin‐based photocatalysts so far. Moreover, blending with the classical electron acceptor, IT‐4F, bulk heterojunction NPs (ZnTPP‐3O:IT‐4F) deliver an impressive HER rate up to 322 mmol g ⁻¹ h ⁻¹ under AM 1.5G sunlight illumination. It demonstrates that introducing OEG chains to organic photocatalysts is an efficient and feasible strategy to regulate the exciton behavior and boost the photocatalytic HER performance.