Owing to their advantageous physical, chemical, electronic, and optical properties, two-dimensional (2D) materials are widely used as highly active visible-light photocatalysts. In this study, 3D/2D composite photocatalysts were prepared from ammonium phosphotungstate nanoparticles and 2D ultrathin graphitic carbon nitride by an impregnation method and were found to efficiently promote the photodegradation of rhodamine B and tetracycline in water under visible light irradiation. Photocatalytic degradation was maximum at a PW12NH4 loading of 20 wt% (UCN20), with photodegradation efficiencies of 93.40% and 69.6% for RhB and TC, respectively. The photocatalytic degradation rate using UCN20 was 5.8-fold higher for RhB and 2.2-fold higher for TC compared to those with UCN. This high performance is ascribed to the large specific surface areas and pore volumes of the composites and the reduced probability of photogenerated carrier recombination therein. The related degradation mechanism is believed to involve a Z-scheme charge transfer mode, which enhances the redox capability of composite photocatalysts and renders them suitable for the visible light-driven remediation of wastewater containing organic contaminants.

The S-doped g-C3N4 (SCN) was prepared by thermal condensation method using thiourea as a precursor, and then the phosphotungstic acid (PTA)/SCN composite photocatalytic material was prepared by reflux adsorption method. The photocatalytic degradation experiments of Rhodamine B showed that SCN20 had the highest photocatalytic degradation rate (74 %), which was 1.9 times and 3.5 times higher than that of PTA (39 %) and SCN (21 %), respectively. The photocatalytic degradation rate of SCN20 was increased by 5 times compared to that of SCN, indicating that the photocatalytic degradation performance of the composite material was significantly improved. The photocatalytic degradation mechanism study revealed that O2- was the main active species in the photocatalytic degradation of Rhodamine B, and the addition of PTA helped the effective separation of electrons-hole and improved the photocatalytic degradation rate. Our PTA/SCN is proposed as an environmental safety tool due to several advantages, such as low cost, convenient preparation, and efficient photocatalytic degradation of Rhodamine B.