Enhancement of visible-light-driven photocatalytic H2 evolution from water over g-C3N4 through combination with perylene diimide aggregates

• Novel solution-processed composite photocatalysts were fabricated feasibly.
• Donor–acceptor perylene diimide assemblies were used as light-absorber for g-C3N4.
• Composite has better visible-light-driven H2 evolution activity than bare Pt/g-C3N4.

Graphitic carbon nitride (g-C3N4) is among the most promising metal-free photocatalysts for H2 production from solar-driven water reduction. However, the photocatalytic efficiency of bulk g-C3N4 powders is limited. In this work, molecular aggregates of perylene tetracarboxylic diimides (PTCDIs, a robust class of air-stable n-type organic semiconductor) were loaded via solution processing on the surface of g-C3N4, which is pre-deposited with cocatalyst Pt nanoparticles. The PTCDIs/Pt/g-C3N4 composites thus fabricated exhibit broader visible-light response than Pt/g-C3N4, and possess excellent photochemical stability. The initial intramolecular charge transfer features of the PTCDIs, as well as their energy levels being matched to g-C3N4, ensure subsequent charge separation in the PTCDIs/Pt/g-C3N4 composites. When the composites are dispersed into aqueous solutions containing triethanolamine as a sacrificial electron donor, a tenfold enhancement of H2 evolution activity (∼0.375 μmol h−1) is achieved compared to bare Pt/g-C3N4 under visible-light (λ ≥ 420 nm) irradiation.

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