Synthesis of novel p-n heterojunction m-Bi2O4/BiOCl nanocomposite with excellent photocatalytic activity through ion-etching method

Fabrication of CuFe2O4/Bi12O17Cl2 photocatalyst with intrinsic p-n junction for highly efficient bisphenol A degradation

The construction and application of novel highly efficient photocatalysts have been the focus in the field of environmental pollutant removal. In this work, a novel CuFe2O4/Bi12O17Cl2 photocatalysts were synthesized by simple hydrothermal and chemical precipitation method. The fabricated CuFe2O4/Bi12O17Cl2 composite exhibited much higher photocatalytic activity than pristine CuFe2O4 and Bi12O17Cl2 in the removal of bisphenol A (BPA) under visible-light illumination, which ascribed to the intrinsic p-n junction of CuFe2O4 and Bi12O17Cl2. The photocatalytic degradation rate of BPA on CuFe2O4/Bi12O17Cl2 with an optimized CuFe2O4 content (1.0 wt.%) reached 93.0% within 30 min. The capture experiments of active species confirmed that the hydroxyl radicals (•OH) and superoxide radicals (•O2-) played crucial roles in photocatalytic BPA degradation process. Furthermore, the possible degradation mechanism and pathways of BPA was proposed according to the detected intermediates in photocatalytic reaction process.

Heterojunction material BiYO3/g-C3N4 modified with cellulose nanofibers for photocatalytic degradation of tetracycline

Cellulose nanofibers (CNFs) with large specific surface area and superb adsorption capacity are excellent photocatalyst carriers. In this study, heterojunction powder material BiYO₃/g-C₃N₄ was successfully synthesized for the photocatalytic degradation of tetracycline (TC). The photocatalytic material BiYO₃/g-C₃N₄/CNFs was obtained by loading BiYO₃/g-C₃N₄ on CNFs using electrostatic self-assembly method. BiYO₃/g-C₃N₄/CNFs exhibit a fluffy porous structure and large specific surface area, strong absorption in the visible light range, and the rapid transfer of photogenerated electron-hole pairs. Polymer-modified photocatalytic materials overcome the disadvantages of powder materials that are easy to reunite and difficult to recover. With synergistic effects of adsorption and photocatalysis, the catalyst demonstrated excellent TC removal efficiency, and the composite maintained nearly 90 % of its initial photocatalytic degradation activity after five cycles of use. The superior photocatalytic activity of the catalysts is also attributable to the formation of heterojunctions, and the heterojunction electron transfer pathway was confirmed by experimental studies and theoretical calculations. This work demonstrates that there is great research potential in using polymer modified photocatalysts to improve photocatalyst performance.

Sunlight promoted self-fenton photodegradation and pathway of doxycycline: Interactive effects of nanomaterial on bean plant and its genotoxicity against Allium cepa

Photocatalytic induction of electron/hole recombination, surface property and light response ability effectively enhance the photocatalytic activity of nanomaterial. In this work, the effective charge carrier separating Sn/Mn-ZnFe₂O₄-CdFe₂O₄-Ag₃PO₄ Quantum dots (M/SZFO-CFO-AP QDs) was fabricated for photocatalytic degradation of doxycycline (doxy) antibiotic. The result showed enhanced photocatalytic activity of doxy and the degradation efficiency of doxy was about 98.8% in short span of time. The calculated WH plot and urbach energy of prepared photocatalyst exhibited evidence for the prevalence of point defects and its contribution to efficient charge separation and transferability. The total organic carbon (TOC) removal was found to be 98.9%, which depicts the complete mineralization of doxy. The synergetic charge transfer of n-p-n heterojunction enables the effective removal of doxy under visible light irradiation. Further, the genotoxicity study was determined by interacting the SZFO-CFO-AP QDs with Allium Cepa. The results depict that SZFO-CFO-AP QDs show lower toxicity level and there were no trace of defective mitotic phases and micro nuclei. Further, the progression and development of bean plant was determined after treating with prepared nanomaterials and the result showed the enhanced growth in SZFO-CFO-AP QDs treated bean plant compared to the counterparts. Therefore, the prepared SZFO-CFO-AP QDs was can be used as an environmental friendly photocatalyst for effective treatment of antibiotic present in the water bodies.

Improving the Surface Oxygen Vacancy Concentration of Bi2O4 through the Pretreatment of the NaBiO3·2H2O Precursor as a High-Performance Visible Light Photocatalyst

The oxygen-deficient bismuth oxide, Bi₂O₄, synthesized by a typical hydrothermal method using commercial NaBiO₃·2H₂O as a raw material only has a relatively low concentration of surface oxygen vacancies (OVs). How to improve the visible light photocatalytic performance of Bi₂O₄ via tuning its surface OV concentration is still a huge challenge. In this study, improving the surface OVs of Bi₂O₄ was successfully realized through the pretreatment of commercial NaBiO₃·2H₂O, including thermal treatment in air and hydrothermal treatment in 10 M NaOH solution, forming NaBiO₃·xH₂O intermediate products first, and then hydrothermal preparation of Bi₂O₄ target products using NaBiO₃·xH₂O instead of commercial NaBiO₃·2H₂O as the precursor. The enhanced surface OV content not only narrows the band gap of Bi₂O₄ and thus extends its optical response range but also captures more photoexcited electrons and thus increases the charge carriers' separation efficiency and prolongs the charge carriers' lifetime of Bi₂O₄. Among the above-mentioned two pretreatment methods, the effects of the hydrothermal pretreatment are superior to those of the thermal treatment, involving the increase of surface OVs, the optical harvesting capacity, and the charge carriers' separation efficiency. Accordingly, Bi₂O₄ prepared by the hydrothermal pretreatment route exhibits the optimal visible light catalytic performance toward the removal of methyl orange (MO) and phenol due to its most abundant surface OV concentration, which is 2.59 times and 4.26 times higher than that of Bi₂O₄ synthesized directly by the commercial NaBiO₃·2H₂O route, respectively. Holes (h⁺) and superoxide radicals (^•O₂^-) are identified as the main active species, while singlet oxygen (¹O₂) and hydroxyl radicals (^•OH) are verified as the second and third important active species for organic pollutant removal, respectively. This work has developed a novel strategy to promote the catalytic performance of single Bi₂O₄ induced by the enhanced surface OV concentration through the pretreatment of the precursor, commercial NaBiO₃·2H₂O.

Persulfate assisted photocatalytic degradation of tetracycline by bismuth titanate under visible light irradiation

Tetracycline is a commonly used broad-spectrum antibiotic to prevent and cure the bacterial infections. However, the incompletely metabolic tetracycline molecules by organisms discharged into aquatic environment increase the ecological toxicity....

A Review: Photocatalysts Based on BiOCl and g-C3N4 for Water Purification

Many organic pollutants are discharged into the environment, which results in the frequent detection of organic pollutants in surface water and underground water. Some of the organic pollutants can stay for a long time in the environment due to their recalcitrance. Advanced oxidation processes (AOPs) can effectively treat the recalcitrant organic compounds in water. Photocatalysis as one of the AOPs has attracted a lot of interest. BiOCl and g-C3N4 are nice photocatalysts. However, their catalytic activity should be further improved for industrial utilization. The construction of heterojunction between the two different components is deemed as an efficient strategy for developing a highly efficient photocatalyst. As a typical type-II heterojunction, g-C3N4/BiOCl heterojunctions showed better photocatalytic performance. To date, the g-C3N4/BiOCl composites were mainly studied in the field of water purification. The photoactivity of the pristine catalysts was greatly enhanced by the combination of the two materials. However, three kinds of proposed mechanisms were used to explain the improvement of the g-C3N4/BiOCl heterojunctions. But few researchers tried to explain why there were three different scenarios employed to explain the charge transfer. According to the articles reviewed, no direct evidence could indicate whether the band structures of the heterojunctions based on BiOCl and g-C3N4 were changed. Therefore, many more studies are needed to reveal the truth. Having a clearer understanding of the mechanism is beneficial for researchers to construct more efficient photocatalysts. This article is trying to start a new direction of research to inspire more researchers to prepare highly effective photocatalysts.

Heterojunction photocatalysts for degradation of the tetracycline antibiotic: a review

Antibiotic pollution is a major health issue inducing antibiotic resistance and the inefficiency of actual drugs, thus calling for improved methods to clean water and wastewater. Here we review the recent development of heterojunction photocatalysis and application in degrading tetracycline. We discuss mechanisms for separating photogenerated electron-hole pairs in different heterojunction systems such as traditional, p-n, direct Z-scheme, step-scheme, Schottky, and surface heterojunction. Degradation pathways of tetracycline during photocatalysis are presented. We compare the efficiency of tetracycline removal by various heterojunctions using quantum efficiency, space time yield, and figures of merit. Implications for the treatment of antibiotic-contaminated wastewater are discussed.

Hollow porous BiOCl microspheres assembled with single layer of nanocrystals: spray solution combustion synthesis and the enhanced photocatalytic properties

The hollow porous microspheres assembled with BiOCl nanocrystals were successfully synthesized via a facile spray solution combustion synthesis method. The microstructure, morphology, absorbance, optical properties of the samples were investigated in detail. The results show that hollow porous BiOCl microspheres have narrow band gaps (2.66-2.71 eV), and the degradation rate of rhodamine B (RhB) can reach 98% under visible light irradiation for 60 min. Furthermore, the mechanism of the photocatalytic degradation of RhB was proposed through the experiment of trapping active species. This excellent photocatalytic property can be ascribed to the larger specific surface area and the special microstructure.

Incorporating W cations into ZnO nanosheets: an efficient method towards ZnO/ZnWO4 photocatalysts for highly effective degradation of organic compounds under UV and visible-light irradiation

Novel ZnO/ZnWO₄ photocatalysts were synthesized for the removal of RhB dye with an excellent photocatalytic performance.

Construction of a rod-like Bi2O4 modified porous g-C3N4 nanosheets heterojunction photocatalyst for the degradation of tetracycline

The solar-powered semiconductor photocatalytic technology for pollutant degradation has been widely studied for its potential to alleviate the current environmental crisis.