In order to construct a magnetic recyclable photocatalyst with superior photocatalytic performance and stability, Ag/AgBr photocatalysts modified by magnetic CoFe2O4 nanoparticles (NPs) were synthesized via deposition–precipitation followed by a solvothermal process. Such a synthesis strategy allows the even dispersion of CoFe2O4 NPs on the surface of Ag/AgBr. Besides, a Z-scheme photocatalyst with metallic Ag as a solid-state electron mediator was formed, which exhibits excellent photocatalytic activity and stability for photocatalytic degradation of hardly decomposed colorless phenol compounds, namely, endocrine disrupting chemical bisphenol A (BPA) and 4-chlorophenol (4-CP), in an aqueous solution. The results showed that the Ag/AgBr@CoFe2O4 composites not only exhibited enhanced photocatalytic performance but also improved stabilities. More importantly, the photocatalysts could be recycled easily by an external magnetic field. The antibacterial activity of the Ag/AgBr@CoFe2O4 composites have been investigated by eliminating Escherichia coli (E. coli) in water under visible light irradiation, and the results revealed that the Ag/AgBr@CoFe2O4 composites possessed good photocatalytic antibacterial activity. At last, the enhanced photocatalytic mechanisms were discussed by investigating the main reactive species in the photocatalytic process, which revealed that the photo-generated holes (h+) and O2˙− were the main reactive species.

A novel visible-light-driven Ag2S/SnS2 composite photocatalyst was successfully fabricated via a simple in situ hydrothermal-ion-exchange method. The materials were systematically characterized by various techniques. XRD, XPS, and TEM analysis demonstrated the successful formation of Ag2S quantum dots on the surface of SnS2 nanoplates. The Ag2S/SnS2 composite materials exhibited increased photocatalytic activity compared to pure SnS2 for the removal of methyl orange (MO) and Cr(VI), and the 1% Ag2S/SnS2 composite material showed the best activity under visible light irradiation. Holes (h+) and superoxide radicals (˙O2−) were the major active species during the photocatalytic process. The in situ formation of Ag2S quantum dots provided an effective way to facilitate carrier transfer and separation, which is believed to be responsible for the enhanced photocatalytic performance.

•Sesame ball like Ag3PO4@CoFe2O4 nanostructure magnetic photocatalyst was synthesized successfully.•The Ag3PO4@CoFe2O4 photocatalysts exhibit excellent photocatalytic disinfection and organic pollutants degradation.•Revealed that modification of CoFe2O4 facilitated the O2 adsorption and OO bond activation/cleavage/oxide removal.•Demonstrated that the surface catalysis engineering can serve as a versatile approach to refine catalysts.In this work, a novel Ag3PO4@CoFe2O4 composite photocatalyst was synthesized via a phosphate salts alkalinity adjustment strategy. Structure, morphology, and chemical component analysis indicated that the magnetic CoFe2O4 nanoparticles (NPs) were evenly decorated on the surface of Ag3PO4 particles, forming a sesame ball like structure. This unique structure ensures that the Ag3PO4@CoFe2O4 composites could be totally separated by the magnet field. Photocatalytic water disinfection and organic pollutants degradation were employed to evaluate the photocatalytic performance of the as-prepared magnetic photocatalysts. The results showed that the optimum 3% Ag3PO4@CoFe2O4 composite could completely inactivate 1*107 cfu/mL of Escherichia coli within 40 min, much faster than the pristine Ag3PO4. Meanwhile, the 3% Ag3PO4@CoFe2O4 composite also showed a dramatic enhancement of photocatalytic activities for the organic pollutants degradation. The reactive oxygen species yield measurements, O2 control photocurrents experiments, O2-TPD tests and photoluminescence spectra analysis indicate that the surface modification of CoFe2O4 NPs could facilitate the O2 adsorption and OO bond activation/cleavage/oxide removal and accelerate the two-electron oxygen reduction reaction for H2O2 generation on the surface of Ag3PO4, and thus more ROSs were generated. In addition, due to the acceleration of electrons consumption, more holes will be left for the organic pollutants oxidation, and the photocatalytic activities as well as stability of Ag3PO4 therefore have been greatly improved.The CoFe2O4 NPs possess specific catalyzing properties, which can effectively catalyze the two-electron oxygen reduction reaction for H2O2 generation on the surface of Ag3PO4@CoFe2O4 composites. The photocatalytic water disinfection and organic pollutants degradation efficiency can be greatly improved.Download high-res image (80KB)Download full-size image

•The new photocatalyst BaFe12O19/g-C3N4 composites were synthesized.•The BaFe12O19/g-C3N4 composites have stable magnetism.•The combination of BaFe12O19 and g-C3N4 could degrade colored and colorless pollutants under H2O2 addition.•The BaFe12O19/g-C3N4 composites possess the ability of thermocatalytic degradation of pollutants.In this article, a new type of magnetic BaFe12O19/g-C3N4 composite photocatalysts were successfully fabricated by combining BaFe12O19 with polymeric g-C3N4. The structures, morphology, optical properties and magnetic property of composites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), infrared (IR) spectra, UV–vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and vibrating sample magnetometer (VSM) respectively. The photocatalytic performance of BaFe12O19/g-C3N4 composites were evaluated by removing Rhodamine B (RhB) and degrading tetracycline with the presence of H2O2 under visible-light irradiation. The optimal percentage of doped BaFe12O19 was 16.8 wt%. As well as 16.8 wt% BaFe12O19/g-C3N4 with the presence of H2O2 can keep high photocatalytic activity after four runs reaction under visible-light irradiation. The enhanced photocatalytic performance could be ascribed to the synergistic effect between BaFe12O19 and g-C3N4, which can facilitate photogenerated charge separation and promote the photo-Fenton process. In addition, the BaFe12O19/g-C3N4 composites have a good magnetic property. After the photocatalytic reaction, the recycling and collection of photocatalyst can be easily achieved. Furthermore, 16.8 wt% BaFe12O19/g-C3N4 can degrade the RhB about 56.6% at 100 min without light irradiation, which is much significantly higher than g-C3N4 and BaFe12O19. The results suggest the combination of g-C3N4 and BaFe12O19 endowed the composite with thermocatalytic degradation ability. It also indicates the synergistic effect between the g-C3N4 and BaFe12O19 play a key role in the degradation reaction.

•The ZnFe2O4/Ag/Ag3VO4 composites were successfully synthesized by a hydrothermal method.•ZnFe2O4/Ag/Ag3VO4 composites showed better photocatalytic activity for MO and TC degradation under visible light.•The ZnFe2O4/Ag/Ag3VO4 photocatalyst is promising for designing an environmental purification material.A novel visible-light driven ZnFe2O4/Ag/Ag3VO4 photocatalyst was successfully fabricated through a two-step hydrothermal method. The structure, morphology and composition of the samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and X-ray photo-electron spectroscopy (XPS). The as-prepared ZnFe2O4/Ag/Ag3VO4 composites possessed an excellent performance in the photocatalytic degradation of methyl orange and tetracycline under visible-light irradiation. The results of electrochemical impedance spectroscopy (EIS) indicated that the ZnFe2O4/Ag/Ag3VO4 composite could facilitate the separation of photo-generated carriers, as well as accelerated charge transfer. The 5% ZnFe2O4/Ag/Ag3VO4 composite exhibited the upmost photocatalytic activity, the degradation constant of 5% ZnFe2O4/Ag/Ag3VO4 is as high as 1.49 times to that of Ag/Ag3VO4. Also, according to the trapping experiments, it’s found that the superoxide radicals (O2−) and hole (h+) were the predominant reactive species in this system. The ZnFe2O4/Ag/Ag3VO4 photocatalyst is promising for designing as an environmental purification material in treatment of antibiotic pollutant.Download high-res image (118KB)Download full-size imageNovel ZnFe2O4/Ag/Ag3VO4 showed much higher photocatalytic activity in degrading MO and TC.

Angstrom-sized tungsten carbide dots (WCdot), WC rods (WCrod) and 10 nm-sized WC particles (WCnano) are synthesized and used as platinum (Pt) electrocatalyst supports for efficient oxygen reduction reaction (ORR). The concentration of the tungsten source and formula structure of the carbon source (ion-exchange resin) control the size and shape of the WC materials. The angstrom-sized WCrod promoted Pt electrocatalyst (Pt/WCrod) shows slightly higher activity than the 10 nm-sized WCnano promoted electrocatalyst (Pt/WCnano), although the WCrod costs only one tenth the W amount of the WCnano, indicating resource saving. In addition, the Pt/WCrod shows higher ORR efficiency and stabilization than the commercial Pt/C. The electron transfer from WC to Pt is believed to account for the excellent performances of the Pt/WC. The significance of the work is that less WC and less Pt can be used to achieve the same or higher ORR performances, and the synthesis method can also be used to synthesize other angstrom-sized materials.