Novel 3D core-shell structured CQDs/Ag3PO4@Benzoxazine tetrapods for enhancement of visible-light photocatalytic activity and anti-photocorrosion

To improve the visible-light photocatalytic activity and anti-photocorrosion of Ag3PO4, novel 3D core-shell CQDs/Ag3PO4@benzoxazine tetrapods with more exposure of {110} facets of Ag3PO4 has been successfully synthesized for the first time by electrochemical oxidation, chemical precipitation and molecular self-assembly reaction. In CQDs/Ag3PO4@benzoxazine tetrapods, CQDs could not only induce more photocarrier generation from high-energy facets of Ag3PO4 tetrapods but also accelerate the electrons transfer from conduction band of Ag3PO4 tetrapods to the bottom of conduction band of CQDs. Furthermore, silver amine complex could act as a bridge for the photo-electrons flowing from core to shell, which is beneficial to the subsequent free radical chain reaction. In addition, the 3D core-shell structure decreased the solubility of Ag3PO4. UV-vis DRS, indicating that the band gap of CQDs(0.38%)/Ag3PO4 @benzoxazine (1.65 eV) was far less than that of Ag3PO4 tetrapods (2.0 eV) and traditional Ag3PO4 (2.45 eV). Moreover, the photocurrent tests showed that CQDs(0.38%)/Ag3PO4@benzoxazine had perfect drift ability of generated photocarriers. Accordingly, the CQDs(0.38%)/Ag3PO4@benzoxazine tetrapods exhibited excellent visible-light photocatalytic activity and anti-photocorrosion performance. More than 93% of Methylorange and rhodamine B could be photodegraded within 16 min and 10 min over CQDs(0.38%)/Ag3PO4@benzoxazine tetrapods, respectively. Even after 9 cycles, CQDs(0.38%)/Ag3PO4@benzoxazine could still remain 95% removal rate of sulfamethoxazole (SMX) with 10 min. Through recycling catalytic experiments and photodegradation pathway explore of SMX, the CQDs(0.38%)/Ag3PO4@ benzoxazine composite suggest its great mineralization capability on sulfonamide antibiotics. The free radicals trapping experiments demonstrated that the holes photoinduced were the main active oxidizing species which played the dominant role in the photocatalytic process. Thus, CQDs(0.38%)/Ag3PO4@benzoxazine is a promising visible-light responses catalyst for photodegradation of organic pollutants in the environmental protection.