Constructing N-Doped KNb3O8/g-C3N4 Composite for Efficient Photocatalytic H2 Generation and Degradation under Visible Light Irradiation

To improve the light harvesting ability and photogenerated carriers separation, N-doped KNb3O8 supported graphitic carbon nitride (g-C3N4) was prepared by a facile calcination method using nitrogen-rich precursor of melamine for the first time. The electric structure of KNb3O8 layers was well regulated by N doping to achieve visible light response. Simultaneously, the formed g-C3N4 was combined with N-doped KNb3O8 to gain heterojunction structure. The separation, transfer and recombination processes of photogenerated charge carriers were investigated by transient photocurrent, electrochemical impedance spectra (EIS) and photoluminescence (PL) measurement. The photocatalytic performances were evaluated by H-2 generation and RhB degradation under visible light irradiation. The sample of N-doped KNb3O8/g-C3N4 (KNCN) exhibited the high photocatalytic performance for H-2 generation and RhB degradation, which is mainly attributed to the synergistic effects of the extended light harvesting ability and effective charge transportation/separation rate by N-doping and heterojunction formation, respectively. A possible mechanism for the photocatalytic degradation of RhB was proposed.