Ternary Z-scheme heterojunction of Bi2WO6 with reduced graphene oxide (rGO) and meso-tetra (4-carboxyphenyl) porphyrin (TCPP) for enhanced visible-light photocatalysis.

A highly efficient and new ternary TCPP/rGO/Bi2WO6 Z-scheme heterojunction was designed and fabricated via a facile hydrothermal approach and a liquid ultrasonic route in sequence. The crystal structures, morphologies, microstructures, chemical compositions, elemental states, optical and photo-electrochemical properties of the heterojunction were characterized. This Z-scheme TCPP/rGO/Bi2WO6 photocatalyst has significantly enhanced photocatalytic activity for the tetracycline (TC) degradation under the irradiation of visible light (λ > 420 nm) within 60 min, as compared to pure Bi2WO6, rGO/Bi2WO6 and TCPP/Bi2WO6 composites. The effects of the photocatalyst dosages, pollutant concentrations, coexisting ions and illumination conditions on the photodegradation were investigated. According to the trapping experiments and electron spin resonance analyses, the hole (h+) and superoxide radical (O2-) mainly contribute to the TC decomposition in the TCPP/rGO/Bi2WO6 photocatalytic system. The photodegradation process in the TCPP/rGO/Bi2WO6 ternary composites can be well described by the proposed Z-scheme mechanism. The results indicate that more efficient charge separation, better light absorption, and larger surface area from the developed photocatalyst collectively contribute to the excellent photocatalytic performances. Besides, the photocatalyst has great stability and recyclability with a removal efficiency of 79.27% even after five times of repeated treatment. This work reports a new strategy for the preparation of Z-scheme heterojunction photocatalyst with high photocatalytic activity and provides an alternative for the effective removal of antibiotic wastewater through photocatalysis.