Positive roles of Br in g-C3N4/PTCDI-Br heterojunction for photocatalytic degrading chlorophenols

In order to efficient photocatalytic degradation of chlorophenols by organic semiconductor perylene tetracarboxylic diimide (PTCDI), two major issues need to be addressed, namely, poor visible light utilization and easy recombination of photogenerated electrons and holes. In this work, we aimed to overcome above issues by in-situ assembling brominated-PTCDI (PTCDI-Br) on g-C3N4 forming g-C3N4/PTCDI-Br heterojunction. It showed obvious visible-light absorption enhancement by the substitution of Br. Meanwhile, Br substitution made the conduction band of PTCDI-Br closer to the valence band of g-C3N4, resulting in the reduced interface electron transfer resistance and the increased internal-electric fields from g-C3N4 to PTCDI-Br, facilitating the interfacial charge transfer. Importantly, there was an enhancement of photocatalytic activity and stability when g-C3N4/PTCDI-Br was used as the photocatalyst for degrading 4-chlorophenol (4-CP) under UV-vis light irradiation. This finding offers new insight into the design strategy for PTCDI-based photocatalysts with excellent performance.