Promoting Photocatalytic Hydrogen Evolution by Stabilization of Excited Triplet States and Enhancement of Internal Electric Field at Dye/PCN Interface.

The heterojunction photocatalysts composed of organic dyes and polymeric carbon nitride (PCN) have great potential for photocatalytic hydrogen evolution (PHE). However, serious charge recombination exists at the dye/PCN interface for the large gaps in time scales and the poor driving force of charge transfer process. Herein, both the excited triplet states of organic dyes with long lifetimes and strong internal electric fields (IEF) as charge transfer driving forces are achieved by the construction of high dipole moments with aromatic-core engineering, and modulation of dye aggregates by alkyl modification. Accordingly, PHE efficiency can achieve up to 833.49 μmol/h, over 36-fold that of PCN/Pt (23.34 μmol/h) under the same conditions. The relationship between molecular structures and PHE performance has been systematically investigated by the photophysical properties of organic dyes and the strength of IEF at dye/PCN interface. It afforded an efficient strategy to balance the charge transfer process in PHE systems, which can guide the molecular design of organic dyes with optimized aggregated behaviors and stable excited triplet states.