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In this paper, three-dimensional TiO2 nanoflowers (NFs) were prepared by a facile hydrothermal method, and Ag3PO4 was grown in situ following alkali treatment to design and synthesize a Ag3PO4/OH/TiO2 catalyst with excellent photocatalytic activity under visible light. The test results show that the photocatalytic degradation performance of TiO2 NFs after alkali treatment and Ag3PO4 loading is significantly improved. This is because the alkali treatment and the introduction of Ag3PO4 can provide a large amount of –OH, which can be converted to ˙OH under UV irradiation, followed by an increase in the number of active radicals to enhance the photocatalytic degradation performance. Meanwhile, the introduction of Ag3PO4 can effectively improve the light absorption ability of the photocatalyst. Moreover, the in situ growth of Ag3PO4 on TiO2 NFs can construct a high-quality Ag3PO4/TiO2 heterojunction to promote the charge separation and transport. Therefore, the degradation rate of Ag3PO4/OH/TiO2 can reach 90% after 30 min for degrading 3 mg L−1 RhB under visible light. The Ag3PO4/OH/TiO2 photocatalyst designed in the present work provides a new tool for the degradation of organic dyes. [ABSTRACT FROM AUTHOR]

In this paper, a series of BN/NTCDA photocatalysts have been prepared using a simple calcination method and their photocatalytic performance under visible light irradiation is studied with tetracycline (TC) as the target pollutant. When the ratio of BN and NTCDA is 100 : 1 and the temperature is 350 °C, the sample (BN/NTCDA (100 : 1)) has the highest adsorption efficiency (28.65%) and photodegradation efficiency (51.54%) for TC. The characterization results of XRD, FTIR, XPS, TEM, and 1H NMR show that BN/NTCDA (100 : 1) is a BN-based photocatalytic material, which is likely formed through the reaction of the surface hydroxyl group of BN and the anhydride of NTCDA. The band gap of BN is about 4.11 eV, and the band gap of NTCDA is 2.67 eV. So, the electron is firstly excited from the VB of NTCDA to its CB, and then the electron in the VB of BN is excited into the empty VB of NTCDA, implying that TC is degraded by photoactive species (˙O2−, h+ and ˙OH) from the VB of BN and CB of NTCDA. The capture experiment of photoactive species suggests that ˙O2− makes the main contribution to TC photodegradation, followed by h+, ˙OH. After five recycle experiments, BN/NTCDA (100 : 1) still has 77.32% removal efficiency for TC. The removal efficiency (80.19%) of BN/NTCDA (100 : 1) is higher than that of TiO2 (75.63%) and g-C3N4 (24.44%). This work contributes to the development of novel metal-free-photocatalysts and the application of photocatalytic technology to the removal of antibiotics. [ABSTRACT FROM AUTHOR]

The development of high-efficiency photocatalytic materials responsive to visible light is one of the most effective ways to address the environmental threats posed by organic dyes in industrial wastewater. In this paper, novel visible-light-responsive nitrogen–sulfur co-doped carbon quantum dots modified ZnO (ZnO/N,S-CQDs) composites with a significantly enhanced photocatalytic degradation performance of Rhodamine B (RhB) were successfully synthesized. Under visible light, the photocatalytic degradation efficiency reached 98.7% over the optimal composite. Besides, the degradation obeyed the pseudo-first-order kinetics model with a photocatalytic rate constant (k) of 0.0473 min−1, which was around 3.71 times higher than that of pure ZnO nanoparticles (0.01273 min−1). In addition, the morphology, size and elemental composition of the ZnO/N,S-CQDs were characterized using TEM, SEM, XRD, FT-IR, and XPS which confirmed the successful synthesis of the composites. Photoluminescence (PL) and transient photocurrent response results indicated an increase in the carrier separation efficiency of ZnO/N,S-CQDs. Based on the active species removal experiment, superoxide radicals (˙O2−) played a leading role in the photocatalytic reactions and a possible photocatalytic degradation mechanism was revealed. These further demonstrate that the N,S-CQDs with varying properties contributed significantly to the enhanced photocatalytic activity of ZnO. Overall, the present method follows the principle of green economy, and novel N,S-CQDs provide a feasible approach for the development of photocatalytic performance of ZnO. [ABSTRACT FROM AUTHOR]

BiVO4, as a visible light catalyst, produces photogenerated electrons and photogenerated holes that are easy to recombine. In this paper, a BiVO4/Ag2O composite was prepared to promote the separation of photogenerated carriers of BiVO4. Compared with BiVO4, the properties and photocatalytic activity of BiVO4/Ag2O were obviously improved. The improvement of BiVO4/Ag2O was reflected in the better separation of photogenerated electrons and photogenerated holes, higher UV-visible maximum absorption wavelength, and stronger ability to degrade doxycycline. The effects of Ag2O on the crystal structure, the morphology and the binding energy of BiVO4 were analyzed by XRD, XPS and SEM, and the existence of a heterojunction in BiVO4/Ag2O was confirmed. The results of capture experiments showed that the photocatalytic processes of BiVO4 and BiVO4/Ag2O produced hydroxyl radicals (˙OH), holes (h+) and superoxide radicals (˙O2−). However, the contribution of active species was different in the two systems. The degradation pathways and intermediate products of doxycycline were analyzed by UPLC-QTOF. This work proposed a new method for the preparation of BiVO4/Ag2O particles with remarkable photocatalytic activity, and provided a reference for the degradation of doxycycline. [ABSTRACT FROM AUTHOR]