Search

Many previous studies have underestimated the role of magnetic components in improving photocatalytic performance. It is significance to explore the migration mechanism of photoinduced carriers in magnetic heterojunction. Here, a magnetic heterojunction, BiOI/BaFe12O19, was synthesized by a simple preparation method. The optimal synthesis conditions and photocatalytic reaction conditions were explored. The growth mechanism of bismuth iodide oxide (BiOI) was elaborated by introducing a micromagnetic field stemming from barium ferrite (BaFe12O19). The electrochemical impedance spectroscopy (EIS), Mott–Schottky curve (MS), transient fluorescence spectrometer (PL), and photocurrent response plot (i ~ t) tests indicated that the BiOI/BaFe12O19 possessed a higher transfer capacity of electrons, higher separation efficiency of photoinduced carriers, stronger photocurrent response, and higher carriers density, compared with pure BiOI. The ultraviolet–visible diffuse reflectance spectrophotometer (UV–vis DRS), electron paramagnetic resonance spectrometer (EPR), MS, and quenching experiments revealed band structure configuration and migration mechanism of photoinduced carriers. The enhancement mechanism of photocatalysis and photocatalytic reaction mechanism was clearly proclaimed in BiOI/BaFe12O19 catalytic system. [ABSTRACT FROM AUTHOR]

The Co-doped SrFe12O19 with small particle size was successfully synthesised via a hydrothermal method for the first time. XRD test indicated that the Co incorporation did not alter the M-type structure for SrFe12O19. Meanwhile, a novel nano-magnetic heterostructure BiOCl/Co-doped SrFe12O19 (BiOCl/SrFe12-xCoxO19) was also synthesised using same method. The heterostructure possessed a low bandgap energy and stable magnetic property. The photocatalytic activity evaluation illustrated that the photodegradation efficiency of Rhodamine B (RhB) reached to 98% after 100-min photocatalytic reaction. Furthermore, RhB photodegradation efficiency using BiOCl/SrFe12-xCoxO19 was still more than 70% after four times reuse. The photocatalytic mechanism was explained in detail. The application of BiOCl/SrFe12-xCoxO19 into the removal of organic contaminants or the control of environmental pollution will be of great value. The research results are beneficial to the promotion of industrial applications of solid-state composites in the fields of environmental engineering and energy utilisation. [ABSTRACT FROM AUTHOR]

A novel magnetic heterojunction photocatalyst TiO2/SrFe12O19 was synthesized from self-made strontium carbonate and Tetra-n-butyl Titanate by ultrasound technique. Acting as magnetic substrate, multifunctional strontium ferrite (SrFe12O19) played an important role in the magnetic heterojunction photocatalyst system. On the one hand, as n-type semiconductors, SrFe12O19 was in contact with TiO2, and a heterojunction was generated. On the other hand, as a hard-magnetic material SrFe12O19 can produce a stable magnetic field. This facilitates the recovery of photocatalyst from reaction solution with an extra magnet. More important, the stable magnetic field stemming from SrFe12O19 can promote separation between photo-induced electrons and holes and enhance the quantum efficiency for TiO2. In this work, we proposed an unprecedented migration mechanism of photoexcited charge carriers. It is hope to provide new insight into photocatalytic mechanism for extending our understanding. [ABSTRACT FROM AUTHOR]

BiVO4/Mn1-xZnxFe2O4 was prepared by the impregnation roasting method. XRD (X-ray Diffractometer) tests showed that the prepared BiVO4 is monoclinic crystal, and the introduction of Mn1-xZnxFe2O4 does not change the crystal structure of BiVO4. The introduction of a soft-magnetic material, Mn1-xZnxFe2O4, was beneficial to the composite photocatalyst's separation from the liquid solution using an extra magnet after use. UV-vis spectra analysis indicated that Mn1-xZnxFe2O4 enhanced the absorption intensity of visible light for BiVO4. EIS (electrochemical impedance spectroscopy) investigation revealed that the introduction of Mn1-xZnxFe2O4 enhanced the conductivity of BiVO4, further decreasing its electron transfer impedance. The photocatalytic efficiency of BiVO4/ Mn1-xZnxFe2O4 was higher than that of pure BiVO4. In other words, Mn1-xZnxFe2O4 could enhance the photocatalytic reaction rate. [ABSTRACT FROM AUTHOR]

BiVO4/Mn1-xZnxFe2O4 was prepared by the impregnation roasting method. XRD (X-ray Diffractometer) tests showed that the prepared BiVO4 is monoclinic crystal, and the introduction of Mn1-xZnxFe2O4 does not change the crystal structure of BiVO4. The introduction of a soft-magnetic material, Mn1-xZnxFe2O4, was beneficial to the composite photocatalyst's separation from the liquid solution using an extra magnet after use. UV-vis spectra analysis indicated that Mn1-xZnxFe2O4 enhanced the absorption intensity of visible light for BiVO4. EIS (electrochemical impedance spectroscopy) investigation revealed that the introduction of Mn1-xZnxFe2O4 enhanced the conductivity of BiVO4, further decreasing its electron transfer impedance. The photocatalytic efficiency of BiVO4/ Mn1-xZnxFe2O4 was higher than that of pure BiVO4. In other words, Mn1-xZnxFe2O4 could enhance the photocatalytic reaction rate. [ABSTRACT FROM AUTHOR]

• SrTiO 3 /BaFe 12 O 19 heterostructure was first synthesized and theoretically constructed. • Ba-ferrite plays a "two birds with one stone" effect to enhance photocatalytic activity and prevent metal ion leaching. • The refractory tetracycline could be rapidly degraded over heterojunction/PMS/Vis system. • The catalytic mechanism was explained on the electronic and atomic level. The photocatalytic activation peroxymonosulfate (PMS) could boost the oxidation capacity of the photocatalytic system by generating multiple active species and improving the separation efficiency of photogenerated charges via PMS electron trapping. Here, SrTiO 3 /BaFe 12 O 19 heterojunction was first synthesized and theoretically constructed. PMS was activated by photocatalysis of heterojunction for the tetracycline (TC) degradation, and the degradation efficiency reached 96.1% within 60 s with a reaction kinetic constant of 0.241 s−1. This degradation efficiency and reaction kinetics were 1.39 and 1.83 times higher than those of the SrTiO 3 /PMS/Vis catalytic system, respectively. Experimental and theoretical calculations identified the active sites for PMS activation and corresponding activation pathways. The energy band structure of the Z-scheme heterojunction and the transfer path of photogenerated charges were constructed by combining the UV-DRS, UPS tests and theoretical calculations. Then, the degradation pathway of TC was proposed based on the molecular orbits structure of TC and dominant active species for TC degradation. The toxicity evaluation indicated that the catalytic system could greatly reduce the TC toxicity. This easily recoverable, highly stable heterojunction is expected to be used in other organic wastewater degradation and practical applications. [ABSTRACT FROM AUTHOR]

Magnetic BiOBr/SrFe12O19 nanosheets were successfully synthesized using the hydrothermal method. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and UV-visible diffused reflectance spectra (UV-DRS), and the magnetic properties were tested using a vibration sample magnetometer (VSM). The as-produced composite with an irregular flaky-shaped aggregate possesses a good anti-demagnetization ability (Hc = 861.04 G) and a high photocatalytic efficiency. Under visible light (λ > 420 nm) and UV light-emitting diode (LED) irradiation, the photodegradation rates of Rhodamine B (RhB) using BiOBr/SrFe12O19 (5 wt %) (BOB/SFO-5) after 30 min of reaction were 97% and 98%, respectively, which were higher than that using BiOBr (87%). The degradation rate of RhB using the recovered BiOBr/5 wt % SrFe12O19 (marked as BOB/SFO-5) was still more than 85% in the fifth cycle, indicating the high stability of the composite catalyst. Meanwhile, after five cycles, the magnetic properties were still as stable as before. The radical-capture experiments proved that superoxide radicals and holes were main active species in the photocatalytic degradation of RhB. [ABSTRACT FROM AUTHOR]

Magnetic photocatalyst BiVO4/Mn-Zn ferrite (Mn1−xZnxFe2O4)/reduced graphene oxide (RGO) was synthesized by a simple calcination and reduction method. The magnetic photocatalyst held high visible light-absorption ability with low band gap energy and wide absorption wavelength range. Electrochemical impedance spectroscopies illustrated good electrical conductivity which indicated low charge-transfer resistance due to incorporation of Mn1−xZnxFe2O4 and RGO. The test of photocatalytic activity showed that the degradation ratio of rhodamine B (RhB) reached 96.0% under visible light irradiation after only 1.5 h reaction. The photocatalytic mechanism for the prepared photocatalyst was explained in detail. Here, the incorporation of RGO enhanced the specific surface area compared with BiVO4/Mn1−xZnxFe2O4.The larger specific surface area provided more active surface sites, more free space to improve the mobility of photo-induced electrons, and further facilitated the effective migration of charge carriers, leading to the remarkable improvement of photocatalytic performance. Meanwhile, RGO was the effective acceptor as well as transporter of photo-generated electron hole pairs. •O2− was the most active species in the photocatalytic reaction. BiVO4/Mn1−xZnxFe2O4/RGO had quite a wide application in organic contaminants removal or environmental pollution control. [ABSTRACT FROM AUTHOR]

Abstract BiOI/Mn x Zn 1-x Fe 2 O 4 magnetic photocatalysts were successfully prepared for the first time. With the degradation of simulated RhB wastewater as a pointer to the photocatalytic reaction and combined with Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–visible diffuse reflectance spectroscopy (UV–vis DRS), and vibrating sample magnetometer (VSM), the reasons influencing the photocatalytic performance of the magnetic photocatalysts were further explored. The excessive or insufficient Mn-Zn ferrite both leads to a relatively low photocatalytic activity. When the calcination temperature reaches to 200 and 400 °C, the photocatalytic activity is enhanced significantly, but the main active component in the photocatalysts has changed from BiOI to Bi 5 O 7 I at 400 °C. The nanocomposites prepared under alcohol water environment with hollow microspheres morphology possess a highly photocatalytic efficiency, and the RhB degradation rate within 4 h in the ethanol water environment is significantly higher than that in pure water (98% vs. 59%). [ABSTRACT FROM AUTHOR]