Magnetic NiFe 2 O 4 /BiOBr composites: One-pot combustion synthesis and enhanced visible-light photocatalytic properties

A critical review on relationship of CeO2-based photocatalyst towards mechanistic degradation of organic pollutant

Nanostructured photocatalysts commonly offered opportunities to solve issues scrutinized with the environmental challenges caused by steep population growth and rapid urbanization. This photocatalyst is a controllable characteristic, which can provide humans with a clean and sustainable ecosystem. Over the last decades, one of the current thriving research focuses on visible-light-driven CeO₂-based photocatalysts due to their superior characteristics, including unique fluorite-type structure, rigid framework, and facile reducing oxidizing properties of cerium's tetravalent (Ce⁴⁺) and trivalent (Ce³⁺) valence states. Notwithstanding, owing to its inherent wide energy gap, the solar energy utilization efficiency is low, which limits its application in wastewater treatment. Numerous modifications of CeO₂ have been employed to enhance photodegradation performances, such as metals and non-metals doping, adding support materials, and coupling with another semiconductor. Besides, all these doping will form a different heterojunction and show a different way of electron-hole migration. Compared to conventional heterojunction, advanced heterojunction types such as p-n heterojunction, Z-scheme, Schottky junction, and surface plasmon resonance effect exhibit superior performance for degradation owing to their excellent charge carrier separation, and the reaction occurs at a relatively higher redox potential. This review attends to providing deep insights on heterojunction mechanisms and the latest progress on photodegradation of various contaminants in wastewater using CeO₂-based photocatalysts. Hence, making the CeO₂ photocatalyst more foresee and promising to further development and research.

Construction of oxygen vacancy assisted Z-scheme BiO2-x/BiOBr heterojunction for LED light pollutants degradation and bacteria inactivation

It is well known that the most important task of photocatalytic technology is to synthesize photocatalysts with compact heterojunction structure and high redox ability. To achieve the goal, a novel Z-scheme BiO_2-x/BiOBr heterojunction containing oxygen vacancy was synthesized by an in-situ generation process. Several techniques, X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) have verified the BiO_2-x/BiOBr heterojunction. XPS and electron spin resonance (ESR) reveals the presence of oxygen vacancy in the BiO_2-x/BiOBr composite. As expected, the BiO_2-x/BiOBr composite showed good performance in removing Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), Rhodamine B (RhB) and tetracycline (TC). The effects of inorganic ions, pH value and water matrix were investigated with many details. The active species and proposed mechanism were revealed by trapping experiment and related characterizations. The synergistic effect of oxygen vacancy and Z-scheme heterojunction makes the BiO_2-x/BiOBr composite possess excellent photocatalytic activity.

Z-scheme binary 1D ZnWO4 nanorods decorated 2D NiFe2O4 nanoplates as photocatalysts for high efficiency photocatalytic degradation of toxic organic pollutants from wastewater

In this study, dimensionally coupled Z-scheme binary nanocomposites from two-dimensional (2D) NiFe₂O₄ nanoplates and one-dimensional (1D) ZnWO₄ nanorods are prepared for efficient degradation of an antibiotic tetracycline (TC) and organic dye rhodamine B (RhB) under solar illumination. NiFe₂O₄/ZnWO₄ nanocomposites were synthesized by a simple and ecological in-situ hydrothermal method without the use of surfactants. Structural and morphological studies revealed the formation of heterostructure and 1D ZnWO₄ nanorods were uniformly distributed over the surface of NiFe₂O₄ nanoplates. Light-harvesting capability was improved and optimized by loading with different amounts of ZnWO₄. Photoluminescence analysis demonstrated inhibited nature of the recombination of photo-excited charge carriers in the nanocomposites. Photocatalytic experiments revealed that the nanocomposite exhibited improved Z-scheme electron-transfer for the degradation of TC under solar illumination. In particular, NFZW-20 nanocomposite demonstrated superior photocatalytic degradation of TC of approximately 98% within 105 min. Furthermore, their photocatalytic performance was investigated by RhB dye under the solar irradiation to achieve 98% of degradation of RhB in 70 min. Improved photocatalytic activities are attributed to the Z-scheme electron-transfer mechanism, which could enhance the superior ability of light absorption and reduced recombination rate of the photogenerated charge carriers.

A novel n-type CdS nanorods/p-type LaFeO3 heterojunction nanocomposite with enhanced visible-light photocatalytic performance

In this work, a novel n-type CdS nanorods/p-type LaFeO3 (CdS NRs/LFO) nanocomposite was prepared, for the first time, via a facile solvothermal method. The as-prepared n-CdS NRs/p-LFO nanocomposite was characterized by using powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray spectroscopy (EDX), UV-visible diffuse reflection spectroscopy (DRS), vibrating sample magnetometry (VSM), photoluminescence (PL) spectroscopy, and Brunauer-Emmett-Teller (BET) surface area analysis. All data revealed the attachment of the LFO nanoparticle on the surface of CdS NRs. This novel nanocomposite was applied as a novel visible light photocatalyst for the degradation of methylene blue (MB), rhodamine B (RhB) and methyl orange (MO) dyes under visible-light irradiation. Under optimized conditions, the degradation efficiency was 97.5% for MB, 80% for RhB and 85% for MO in the presence of H2O2 and over CdS NRs/LFO nanocomposite. The photocatalytic activity of CdS NRs/LFO was almost 16 and 8 times as high as those of the pristine CdS NRs and pure LFO, respectively. The photocatalytic activity was enhanced mainly due to the high efficiency in separation of electron-hole pairs induced by the remarkable synergistic effects of CdS and LFO semiconductors. After the photocatalytic reaction, the nanocomposite can be easily separated from the reaction solution and reused several times without loss of its photocatalytic activity. Trapping experiments indicated that ·OH radicals were the main reactive species for dye degradation in the present photocatalytic system. On the basis of the experimental results and estimated energy band positions, the mechanism for the enhanced photocatalytic activity was proposed.

Fabrication and photocatalytic property of magnetic SrTiO3/NiFe2O4 heterojunction nanocomposites

Novel multifunctional SrTiO3/NiFe2O4 nanocomposites were successfully fabricated via a two-step route. The as-prepared samples were characterized by using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), field-emission transmission electron microscopy (TEM), UV-visible diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) spectroscopy and vibrating sample magnetometry (VSM). The results indicate that the SrTiO3/NiFe2O4 heterostructures are composed of SrTiO3 spheroidal nanoparticles adhered to NiFe2O4 polyhedra. The heterojunction established in the composite material accelerates the process of electron-hole pair separation and boosts the photo-Fenton reaction. Among the samples, 15 wt% SrTiO3/NiFe2O4 nanocomposites exhibit a powerful light response and excellent room temperature ferromagnetism. Subsequently, the photocatalytic degradation of RhB over the as-prepared samples was investigated and optimized, revealing that the 15 wt% SrTiO3/NiFe2O4 nanocomposites exhibit the best photocatalytic activity and stability under simulated solar light irradiation. Furthermore, according to experimental results, the possible mechanism of improved photocatalytic activity was also proposed.

Bi5O7NO3 and Ag/Bi5O7NO3 composites: one-step solution combustion synthesis, characterization and photocatalytic properties

In the present study, Bi₅O₇NO₃ and Ag/Bi₅O₇NO₃ composites, as novel efficient photocatalysts, were synthesized via a one-step solution combustion synthesis (SCS) using bismuth nitrate (Bi(NO₃)₃·5H₂O) as an oxidant, tartaric acid (C₄H₆O₆) as a fuel, and silver nitrate (AgNO₃) as an Ag source.

Fabrication of magnetically separable NiFe2O4/BiOI nanocomposites with enhanced photocatalytic performance under visible-light irradiation

SEM image of as-synthesized NiFe₂O₄/BiOI (NFO/BOI) nanocomposites (a) and schematic illustration of excitation and separation of photo-induced electron–hole pairs for NFO/BOI nanocomposites (b).

Highly efficient visible-light-driven photocatalytic degradation of rhodamine B by a novel Z-scheme Ag3PO4/MIL-101/NiFe2O4 composite

An Ag₃PO₄/MIL-101/NiFe₂O₄ composite was fabricated by an in situ precipitation method. The results implied that introduction of the MOF enhanced the rapid transfer of electrons from Ag₃PO₄ to NiFe₂O₄.

Synthesis and photocatalytic activity of BiOBr nanosheets with tunable crystal facets and sizes

A series of BiOBr nanosheets with tunable exposed facets and crystallite sizes were prepared via a solvent adjustment strategy. The exposed facet and thickness of BiOBr nanosheets are both important for their photocatalytic activity.