Preparation of direct Z-scheme heterojunction La-doped Bi2WO6/CdS with enhanced visible light absorption and its photocatalytic degradation of antibiotics

In this paper, a novel direct Z-scheme heterojunction La-Bi2WO6/CdS composed of 3-dimensional flower-like Bi2WO6 and hexagonally stacked succulent CdS was successfully designed and synthesized. The morphology, optical properties, element valence and crystal structure of the catalysts were systematically characterized. When the dosage of LBC-40 was 1.0 g/L, the degradation rate of oxytetracycline (OTC, 20 mg/L, pH=6) was 85.28%, under low visible light illumination (65 W energy saving lamp) for 120 min and the reaction kinetic constant (0.01336 min-1) was 2.50 and 1.56 times that of pure Bi2WO6 and La-Bi2WO6, respectively. Moreover, La-Bi2WO6/CdS showed good photocatalytic activity for other single antibiotics, mixed antibiotics and antibiotics from different water sources. The photocatalytic activity only decreased by 7.69% after 3 cycles. Furthermore, the possible photocatalytic degradation pathway and photocatalytic mechanism of OTC were proposed. The excellent photocatalytic performance of La-Bi2WO6/CdS is for that the doping of La3+ and the construction of direct Z-scheme heterojunction enhances the visible light absorption capacity and separation efficiency of photogenerated electron-hole pairs. This paper reports a new method, which can provide a reference for the design and development of visible light responsive photocatalysts with excellent photocatalytic properties.