Positive Photocurrent of g-C3N4 Obtained by Compounding with p-Type PEDOT Reveals the Role of the Band Structure in Modulating Charge Transfer Direction

The application of graphitic carbon nitride (g-C3N4) in the field of photoelectrochemistry is booming due to its visible light response, stability, low cost, and environmental compatibility. However, the modulation of the photogenerated charge carriers in the g-C3N4 photoelectrode is still a challenge, especially for the control of the charge transfer direction and the improvement of charge migration rate. In this work, PEDOT was in situ deposited on the surface of g-C3N4 to modify the transfer process of the photogenerated holes. The band structure was investigated based on the valence band and work function. The charge transfer properties were characterized by analyzing the processes of hole transfer, separation, and depolarization. PEDOT is found to play two roles: one is to act as a semiconductor material to form a heterojunction with g-C3N4, regulating the charge transfer direction and promoting the separation efficiency of the photogenerated charge carriers; the other one is to act as a hole transmission medium, promoting the migration and depolarization processes of the photogenerated holes. Therefore, the photoelectrochemical performance of g-C3N4 is greatly improved, which is further verified by the enhanced photoinduced cathodic protection performance, whether with the assistance of hole sacrificial agents or not.