Synthesis of KNbO3/g-C3N4 composite and its new application in photocatalytic H-2 generation under visible light irradiation

High-performance KNbO3/g-C3N4 composite was prepared via a feasible method and first applied in photocatalytic H-2 production from water-methanol solution under irradiation of visible light. The structure and optical property of the synthesized composite were investigated by various techniques, including XRD, XPS, FT-IR, TEM, SEM, DRS, PL, and an electrochemical method. Results indicated that the combining of KNbO3 with g-C3N4 did not affect the optical absorption. However, strong interaction between the two semiconductors was observed, which promotes the fabrication of a heterojunction structure and subsequently improves the separation of photogenerated electrons and holes. Hence, KNbO3/g-C3N4 photocatalyst displayed obviously higher photoactivity than pristine g-C3N4. The photocatalytic hydrogen production rate for the optimal KNbO3/g-C3N4 composite (7.4 wt% KNbO3/g-C3N4) is 180 mu mol g(cat)(-1) h(-1), which is about 3.0 times that of pristine g-C3N4. Cycling tests further proved that KNbO3/g-C3N4 showed good photocatalytic stability. Additionally, the effect of hole sacrificial agent on the photocatalytic activity was also investigated. The KNbO3/g-C3N4 sample showed better performance in the presence of methanol than triethanolamine or EDTA-Na.