Accumulation of localized charge on the surface of polymeric carbon nitride boosts the photocatalytic activity

• The in-planar directional charge transfer of polymeric C 3 N 4 can be realized by surface modification with ethylenediamine. • The increased -NH 2 groups induced the generation of midgap states and accumulation of electrons. • The modified C 3 N 4 exhibits excellent photocatalytic activities for hydrogen evolution and MO degradation. The random mobility of charge carriers is a main factor causing the low photocatalytic efficiency of g-C 3 N 4 . Thus, the controllable migration of charge carriers is a rational strategy to suppress the charge recombination and facilitate charge separation. Herein, an ethylenediamine modified g-C 3 N 4 displays improved photocatalytic activity. The excellent charge separation efficiency is confirmed to be a key factor for the enhancement. The TEM observation after photo-depositing Pt nanoparticles and DFT calculations verify the accumulation of electrons on some areas of g-C 3 N 4 surface. The increased -NH 2 groups significantly tune the electronic structure of g-C 3 N 4 after the modification. The generation of midgap states also affects the charge separation. Our reports provide a simple method to manage the migration of charge carriers and enable electrons directional transfer, which suppresses the recombination and improves the photocatalytic activity.