Highly efficient visible/NIR photocatalytic activity and mechanism of Yb3+/Er3+ co-doped Bi4O5I2 up-conversion photocatalyst

Construction of Z-scheme AgCl/BiOCl heterojunction with oxygen vacancies for improved pollutant degradation and bacterial inactivation

A facile Z-scheme AgCl/BiOCl heterojunction photocatalyst with oxygen vacancies was fabricated by a water-bath method. The structural, morphological, optical and electronic properties of as-synthesized samples were systematically characterized. The oxygen vacancies were confirmed by EPR, which could optimize the band-gap of the AgCl/BiOCl heterojunction and improve the photo-induced electron transfer. The optimized AgCl/BiOCl heterojunction showed excellent photocatalytic degradation efficiency (82%) for tetracycline (TC). Simultaneously, E. coli was completely inactivated within 60 min due to the AgCl/BiOCl heterojunction. The elevated catalytic activity of the optimal AgCl/BiOCl heterojunction was ascribed to the synergistic effect of the enhanced light absorption and effective photoinduced charge carrier separation and transfer. Moreover, the degradation efficiency of the AgCl/BiOCl heterojunction towards ofloxacin, norfloxacin and Lanasol Red 5B was 73%, 74% and 96%, respectively. The experimental factors for the degradation efficiency of TC were also studied. Furthermore, active species trapping experiments indicated that superoxide radicals (˙O2-) were the main reactive species, and the Z-scheme charge transfer mechanism helped to improve the photocatalytic activity.

Recyclable and flexible Bi(Ho3+-Yb3+)OBr/g-C3N4 composite porous fiber for efficient water purification and real-time temperature sensing

Herein, an electrospinning porous nanofiber with large specific surface area, excellent flexibility, remarkable tensile strength, and high stability of thermal degradation has been developed by loading Ho3+/Yb3+ co-doped BiOBr/g-C3N4 (BHY/CN) heterojunction photocatalysts on polyacrylonitrile (PAN) nanofibers. The optimized BHY/CN-2 nanofiber demonstrates outstanding photocatalytic activity for the degradation of 98.83% tetracycline (TC, 60 min) and 99.06% rhodamine B (RhB, 90 min) under simulated sunlight irradiation, and maintains a high level of reusability and recycling stability in three cycles. In addition, temperature monitoring of the catalytic degradation process can be feedback by (5F4, 5S2) → 5I8 and 5F5 → 5I8 radiation transitions of Ho3+ with excellent sensitivity. More importantly, the nanofiber luminescence performance is enhanced by the doping of g-C3N4, which maintain the effective upconversion luminescence properties even in water, providing a reliable reference for real-time monitoring and feedback of the operating temperature, and further expanding the application fields of photocatalysts.

Synergistic effects of rare earth doping and carbon quantum dots on BiOF/Bi2MoO6 heterojunctions for enhanced visible-near-infrared photocatalysis

Herein, we designed and synthesized a series of rare earth doped BiOF/Bi₂MoO₆ heterojunctions. The doping locations of rare earth ions were altered to determine the influence on the visible and near-infrared photocatalytic activity of heterojunctions. It is experimentally and theoretically confirmed that doping with Tm³⁺/Yb³⁺ in one semiconductor of the heterojunction produces superior photocatalytic efficiency than doping in both semiconductors. In addition, the near infrared photocatalytic efficiency strongly relied on upconversion luminescence from the Re³⁺ doped semiconductor in the heterojunction. By further modifying with CQDs, the CQDs/BiOF:Tm³⁺,Yb³⁺/Bi₂MoO₆ sample shows excellent visible and near-infrared photocatalytic performance, with 90% degradation of RhB occurring in the first 20 min under visible irradiation. This can be attributed to the large BET area, efficient photoinduced carrier separation and the upconversion process of the composite. This research will provide a systematic solution for realizing full-spectrum responsive and highly efficient photocatalysis by combination of rare earth ion doping, quantum dot modification and Z-scheme heterojunctions.

Rapid Microwave-Assisted Synthesis of ZnIn2S4 Nanosheets for Highly Efficient Photocatalytic Hydrogen Production

In this study, a facile and rapid microwave-assisted synthesis method was used to synthesize In₂S₃ nanosheets, ZnS nanosheets, and ZnIn₂S₄ nanosheets with sulfur vacancies. The two-dimensional semiconductor photocatalysts of ZnIn₂S₄ nanosheets were characterized by XRD, FESEM, BET, TEM, XPS, UV-vis diffuse reflectance, and PL spectroscopy. The ZnIn₂S₄ with sulfur vacancies exhibited an evident energy bandgap value of 2.82 eV, as determined by UV-visible diffuse reflectance spectroscopy, and its energy band diagram was obtained through the combination of XPS and energy bandgap values. ZnIn₂S₄ nanosheets exhibited about 33.3 and 16.6 times higher photocatalytic hydrogen production than In₂S₃ nanosheets and ZnS nanosheets, respectively, under visible-light irradiation. Various factors, including materials, sacrificial reagents, and pH values, were used to evaluate the influence of ZnIn₂S₄ nanosheets on photocatalytic hydrogen production. In addition, the ZnIn₂S₄ nanosheets revealed the highest photocatalytic hydrogen production from seawater, which was about 209.4 and 106.7 times higher than that of In₂S₃ nanosheets and ZnS nanosheets, respectively. The presence of sulfur vacancies in ZnIn₂S₄ nanosheets offers promising opportunities for developing highly efficient and stable photocatalysts for photocatalytic hydrogen production from seawater under visible-light irradiation.

Achieving improved full-spectrum responsive 0D/3D CuWO4/BiOBr:Yb3+,Er3+ photocatalyst with synergetic effects of up-conversion, photothermal effect and direct Z-scheme heterojunction

The key to obtain effective photocatalysts is to increase the efficiency of light energy conversion, and thus the design and implementation of full-spectrum photocatalysts is a potential approach to solve this problem especially by extending the absorption range to near-infrared (NIR) light. Herein, the improved full-spectrum responsive CuWO₄/BiOBr:Yb³⁺,Er³⁺ (CW/BYE) direct Z-scheme heterojunction was prepared. The CW/BYE with CW mass ratio of 5% had the best degradation performance, and the removal rate of tetracycline reached 93.9% in 60 min and 69.4% in 12 h under visible (Vis) and NIR light, respectively, which were 5.2 and 3.3 times of BYE. According to the outcome of experimental, the reasonable mechanism of improved photoactivity was put forward on the basis of (i) the up-conversion (UC) effect of Er³⁺ ion to convert NIR photon to ultraviolet or visible light, which can be used by CW and BYE, (ii) the photothermal effect of CW to absorb the NIR light, increasing the local temperature of photocatalyst particle to accelerate the photoreaction, and (iii) the formed direct Z-scheme heterojunction between BYE and CW to boost the separation of photogenerated electron-hole pairs. Additionally, the excellent photostability of the photocatalyst was verified by cycle degradation experiments. This work opens up a promising technique for designing and synthesizing full-spectrum photocatalysts by utilizing synergetic effects of UC, photothermal effect and direct Z-scheme heterojunction.

Efficient Removal of Inorganic and Organic Pollutants over a NiCo2O4@MOF-801@MIL88A Photocatalyst: The Significance of Ternary Heterojunction Engineering

Energy problems are a substantial concern in a global society that can be solved by replacing with sustainable energies. In recent years, designing nanomaterials as photocatalysts that can produce chemical energy with the utilization of infinite visible light energy became a new solution for water treatment. In the present study, NiCo₂O₄@MOF-801 has been synthesized with multiple properties, and then, a novel three-layer NiCo₂O₄@MOF-801@MIL88A photocatalyst has been successfully synthesized to improve meropenem degradation and Cr(VI) reduction. The prepared photocatalyst was characterized by XRD, IR, XPS, TEM, SEM, TGA, BET, EIS, PL, and UV-vis. According to the structural and optical analysis performed, the interaction between the components formed a heterojunction structure that prevented the recombination of charge carriers and increased the photocatalytic performance. Photocatalytic simulation tests also proved the reduction of chromium and degradation of antibiotics to find the optimal heterogeneous performance. As a result, the NiCo₂O₄@MOF-801@MIL88A composite can completely reduce Cr(VI) in 45 min, which is strongly preferable to any pure component's performance. Overall, this work offers a low-cost but high-efficiency material that can remove organic and inorganic contaminants from water.

Visible-near-Infrared Light-Driven Photocatalytic Characteristics of Er3+/Yb3+-Codoped BiOBr Upconverting Microparticles for Tetracycline Degradation

To settle the unsatisfying efficiency and insufficient light harvesting ability of photocatalysts, we report on the development of Er³⁺/Yb³⁺-codoped BiOBr (BiOBr:Er³⁺/xYb³⁺) microparticles that were synthesized by a rational high-temperature solid-state reaction method. The prepared microcrystals exhibit high visible upconversion (UC) emissions with maximum intensities at x = 0.01 when excited by a 980 nm laser. Remarkably, the corresponding UC emission process is attributed to a two-photon absorption route. Furthermore, the photocatalytic activities of as-synthesized compounds were further evaluated through analyzing the visible-near-infrared light-triggered tetracycline degradation. Compared with BiOBr:Er³⁺ microparticles, BiOBr:Er³⁺/xYb³⁺ microparticles present superior photocatalytic properties and the optimal status is achieved when x = 0.05, in which h⁺, ·O₂^-, and ·OH active species contribute to the photocatalytic mechanism. Additionally, the designed microparticles exhibit better photocatalytic abilities than previously reported photocatalysts (i.e., TiO₂, SnO₂) upon full-spectrum light irradiation. These results reveal that Yb³⁺ codoping is able to not only enhance the UC emission properties of BiOBr:Er³⁺ microparticles but also reinforce their photocatalytic activities. Our findings may put forward a facile strategy to regulate the photodegradation capacity of photcatalysts.

In situ low-temperature pyrolysis fabrication type II BiOIO3/Bi4O5I2 heterostructures with enhanced visible-light-driven photooxidation activity

Novel visible-light-driven heterostructure semiconductors are considered as promising photocatalysts for the elimination of environmental organic pollutants. Herein, a solvent-assisted low-temperature in situ calcination strategy was developed to fabricate type II BiOIO₃/Bi₄O₅I₂ heterojunction by using BiOIO₃ as self-sacrificed template. The phase transition temperature of BiOIO₃ was reduced under solvent-assisted operating conditions. By controlling the elevated temperature from 200 to 300 °C, an in situ stepwise pyrolysis reaction occurred during the calcination process, which was described as BiOIO₃ → BiOIO₃/Bi₄O₅I₂ → Bi₄O₅I₂. The light absorption edge of different samples significantly red shifted from 385 to 632 nm with the increase of calcination temperature. Meanwhile, two interlocked interface lattice fringes were identified in high resolution transmission electron microscope (HRTEM) of BiOIO₃/Bi₄O₅I₂-250 composites, confirming the formation of BiOIO₃/Bi₄O₅I₂ heterojunction. The as-obtained BiOIO₃/Bi₄O₅I₂ heterojunction demonstrated the optimal photodegradation performance, which brought about 99.4% of bisphenol A (BPA) degraded within 30 min visible light (λ > 420 nm) illumination. Besides, after 5 repeated cycles, the photoactivity of BiOIO₃/Bi₄O₅I₂ heterojunction still maintained 91.5%, unfolding its high photostability. The superior photoreactivity of BiOIO₃/Bi₄O₅I₂ nanosheets was assigned to the formation of well-matched type II heterojunction, which significantly enhanced the separation and migration of photoinduced charge carriers. Superoxide radical (O₂^-) and hole (h⁺) are dominant reactive species in this photodegradation system. Based on active species quenching experiments and electron paramagnetic resonance (ESR) measurements, a possible type II heterojunction mechanism for enhanced photodegradation performance of BiOIO₃/Bi₄O₅I₂ heterostructure was proposed. This work affords an innovative method for design and construction of type II composites toward sustainable water purification.

Direct observation of carrier migration in heterojunctions to discuss the p-n and direct Z-scheme heterojunctions

Type II p-n heterojunction and direct Z-scheme heterojunction are identical staggered band alignments, but were reported ambiguously in many composite photocatalysts because their carriers migrate in opposite directions. In this research, metal oxides CuO, NiO and Co₃O₄-based heterojunctions with Na_0.9Mg_0.45Ti_3.55O₈(NMTO) were synthesized via a simple hydrothermal method. The CuO/NMTO heterojunction was demonstrated as a direct Z-scheme heterojunction, whereas the NiO/NMTO and Co₃O₄/NMTO heterojunctions showed type II p-n band alignment, distinguished by the direct observation of carrier migration under light illumination, and confirmed by the x-ray photoelectron spectroscopy, Mott-Schottky measurements, ultraviolet photoelectron spectra and capture experiments. These all heterojunctions enjoyed better photocatalytic performance to degrade methylene blue and antibiotics (Enrofloxacin, Metronidazole and tetracycline) than the pure NMTO, attributed to their effective separation of the photoinduced electron-hole pairs owing to the staggered band alignment. Prominently, the NiO/NMTO and Co₃O₄/NMTO p-n heterojunctions exhibited superior degradation ability to the CuO/NMTO Z-scheme heterojunction. The initial relative Fermi position of two semiconductors is the prerequisite to determine whether the p-n heterojunction or direct Z-scheme heterojunction is built because the electrons diffuse from one semiconductor with a higher Fermi level to another with a lower Fermi level while the holes diffuse reversely until a united Fermi level when they combine. The built-in electric field at the heterojunction interface is determined by the difference in the initial Fermi levels or work functions of two semiconductors, regulating the separation ability of photogenerated electrons and holes to affect the photocatalytic performance. Thus, the high difference in the initial Fermi levels of semiconductors is crucial in the development of heterojunctions with staggered band alignment to obtain high performance in photocatalytic reactions.

Review on long afterglow nanophosphors, their mechanism and its application in round-the-clock working photocatalysis

Semiconductor assisted photocatalysis is one of the most efficient methods for the degradation of complex organic dyes. A major limiting factor of semiconductor assisted photocatalysis is the requirement of a continuous source of light to perform a redox reaction. One of the upcoming solutions is photon energy-storing long afterglow/persistent phosphors. They are an unusual kind of rechargeable, photon energy capturing/trapping phosphors that can trap charge carriers (electrons/holes) in their meta-stable energy levels, thereby resulting in persistent luminescence. Persistence luminescence from such materials can range from minutes to hours. The coupling of long afterglow phosphors (LAP) with the conventional semiconductor is a promising way to support the photocatalytic process even in dark. In addition, dissimilar band structures of LAPs and semiconductor results in formation of heterojunction which further suppresses the recombination of charge. Such an encouraging idea of LAP for round-the-clock working photocatalytic system is in its premature stage; which is required to be investigated fully. Thus, we present a state-of-art review on the potential materials for assisting round-the-clock photocatalysis, trapping-detrapping mechanism in LAP materials, fabrication strategies and their associated characterization tools. Review also covers LAP materials and their photocatalytic mechanism briefly.

Strategies based review on near-infrared light-driven bismuth nanocomposites for environmental pollutants degradation

Recently, solar energy has been considered the most vulnerable source to resolve environmental pollution and energy scarcity problems. Researchers have made intense research efforts to convert solar energy into chemical energy through photocatalysis processes as it is a green, clean and renewable energy source. Numerous discovered photocatalysts show absorption in the ultraviolet-visible (UV∼5% and visible ∼43%) region and are devoid of near-infrared (NIR ∼52%) light utilization. As infrared (IR) light contains a top portion of the solar spectrum; therefore, many alluring and attractive practical strategies have been explored to improve photocatalytic reactions and to harness full solar spectrum (including NIR light). Among those strategies, bandgap engineering, coupling with carbon quantum dots, heterostructure formation, mingling with plasmonic and upconversion (UC) NPs are more worthwhile. In different visible light-assisted photocatalysts, bismuth typically covers a distinctive, favorable, and earth-abundant group of freshly discovered innovative photocatalytic nanomaterials. Bi-based photocatalysts have suitable/good optoelectronic properties, crystalline geometric conformations, amendable electronic structure, and outstanding visible-light responsive range, helpful in environmental remediation and energy transformation. Due to the outstanding photo-oxidization/photodegradation capability of NIR-driven photocatalysts, bismuth-based nanomaterials have been considered suitable photocatalysts for inclusive solar energy utilization. Henceforth, keeping in mind the benefits of bismuth nanomaterials, the present review is focused on NIR-based modification strategies to upgrade solar light absorption of bismuth-based photocatalysts in the NIR region by making it NIR responsive photocatalyst. We have also discussed the photocatalytic applications of bismuth-based NIR responsive photocatalysts in pollutant degradation.

Visible-NIR light-responsive 0D/2D CQDs/Sb2WO6 nanosheets with enhanced photocatalytic degradation performance of RhB: Unveiling the dual roles of CQDs and mechanism study

Environmental pollution caused by dye wastewater discharge has attracted much attention in the past decades. Developing photocatalysts with high solar energy utilization efficiency for the treatment of dye wastewater is one of the most promising methods to address afore-mentioned environmental problem. Herein, novel Vis-NIR (visible to near-infrared) light-responsive carbon quantum dots modified Sb₂WO₆ (CQDs/Sb₂WO₆) nanosheets with remarkably enhanced photocatalytic degradation performance of Rhodamine B (RhB) aqueous solution were successfully synthesized. Under the irradiation of Vis light, the photocatalytic degradation efficiency reaches 83% over the optimal composite, which is nearly seven times higher than that of pristine Sb₂WO₆. Meanwhile, under NIR light irradiation, the optimal composite also keeps a stable degradation performance, while pristine Sb₂WO₆ exhibits sluggish performance. Besides, a detailed photocatalytic degradation pathway was proposed via the analyses of corresponding intermediates in the photocatalytic degradation process. On the basis of electron spin resonance spectrometry, quenching experiment and density functional theory (DFT) calculation, hydroxyl radicals (•OH) play a dominating role in the photocatalytic reactions and a possible photocatalytic degradation mechanism was unearthed. This work provides new insights for constructing novel Vis-NIR responsive photocatalysts to purify dye wastewater for environmental remediation.

Eliminating pesticide quinalphos from surface waters using synthesized GO-ZnO nanoflowers: Characterization, degradation pathways and kinetic study

The presence of highly toxic and persistent pesticides in water bodies causes serious problems to human beings as well as aquatic life. Quinalphos is one such widely used organophosphorus pesticide in agricultural fields. Herein, for degradation and mineralization of quinalphos, ZnO nanoflowers and their hybrid nanocomposite with graphene oxide have been synthesized. FESEM analysis confirmed the formation of ZnO nanoflowers over nanosheets of graphene oxide having a thickness of 20 ± 10 nm. GO-ZnO composite exhibited remarkable photocatalytic activity in comparison to pure ZnO. 98 % degradation of quinalphos was achieved using GO-ZnO nano-catalyst at 6 pH within 45 min of irradiations, whereas it was 80 % for bare ZnO nanoflowers. Higher degradation with hybrid nanocomposite was attributed to improved surface area (36 m² g^-1), a substantial reduction in bandgap energy from 3.10 to 2.90 eV and enhanced charge separation (e^-/h⁺ pairs) after the addition of GO. Reaction kinetics study followed pseudo-first-order behaviour. Further, mineralization to the extent of 90 % in 90 min was confirmed by TOC analysis. Based on identified intermediates, using LCMS analysis, degradation pathways were proposed. The plausible pathways confirmed the presence of smaller and safer reaction intermediates supported by excitation of e^- from nanocomposite followed by oxidation of quinalphos with huge free radicals. Overall, this study is significant in terms of using photocatalysis as a tertiary treatment of quinalphos pesticide wastewater at pH 6 in a short duration.

l-Cysteine directing synthesis of BiOBr nanosheets for efficient cefazolin photodegradation: The pivotal role of thiol

Cefazolin (CFZ) is widely present in the wastewater treatment effluents and in receiving waters and has caused severe impacts to the ecosystem. CFZ degradation by photocatalysis has attracted increasing attention due to its eco-friendly features. Herein, we presented a green synthesis strategy for a highly active BiOBr photocatalyst for CFZ removal with L-cysteine as a directing agent, and the role of thiol in cysteine for facets control and morphology regulation was discussed. We found that the photoactivity of cysteine-induced BiOBr nanosheet was much higher than those prepared by using arginine and glycine as directing agent. Further experiments showed that the cysteine preferentially coordinated Bi³⁺ with thiol rather than carboxyl. The strong interactions of thiol group with the external surface of the BiOBr crystals stabilize the small crystals that have high surface energy without the cysteine. Such a chemical environment favors forming BiOBr crystalline with small size of high surface area and oriented growth in [110] direction, which facilitates the photogenerated electron-hole separation to achieve significantly promoted photocatalytic activity. Moreover, the cysteine-directed BiOBr nanosheets displayed good photoreactivity to more pollutants (i.e. rhodamine B, cefradine and cefoperazone sodium) and excellent reusability as verified via seven consecutive recycle experiments. The proper photocatalyst dosage (0.4 g/L), relatively acidic water environment (pH 3.4) and high temperature (35 °C) would be beneficial to CFZ photodegrdation by BiOBr. Also, the CFZ photodegradation mechanism and degradation pathway were also proposed by combining radical trapping experiments and electron spin resonance (ESR) test with LC-MS analysis in the photocatalytic process.

Phase transformation and heterojunction construction of bismuth oxyiodides by grinding-assisted calcination in the presence of thiourea and their photoactivity

Bismuth-rich oxyhalides are promising photocatalysts due to their special layered structure and adjustable band gap energy. In this work, a series of bismuth oxyiodides were fabricated by grinding-assisted calcination in the presence of thiourea, where grinding-induced mechanical force could accelerate the decomposition reaction and thiourea could prohibit the crystal particles from growing due to coordination action. The combined effect of grinding and thiourea could decrease the temperature of phase transformation of bismuth oxyiodides. Among these, heterojunction Bi4O5I2/Bi5O7I containing uniform flower-like microspheres assembled by ultra-thin nanosheets exhibited the highest photocatalytic activity and favorable stability for the degradation of the antibiotic tetracycline under visible light irradiation. This work could provide a good reference for the design of bismuth-rich oxyhalide heterojunction for photocatalytic applications.

Synthesis, characterization, optoelectronic and photocatalytic properties of Sr2Bi2O5/SrCO3 and Sr3Bi2O6/SrCO3 heterostructures with varying SrCO3 content

We report on the structure and properties of novel Sr₂Bi₂O₅/SrCO₃ and Sr₃Bi₂O₆/SrCO₃ heterostructures with SrCO₃ content varying from 10 wt% to 90 wt%. Formation of the heterostructures is succeeded via sintering technique and according to XRD, SEM, and EDX studies has resulted in highly crystalline materials with well-defined carbonate-bismuthate interfaces. In the reaction of photodegradation of phenol in aqueous solution the heterostructures demonstrated photocatalytic activity exceeding that of TiO₂. It is demonstrated that their photocatalytic action is due to the presence of type II semiconductor heterojunctions. The content of SrCO₃ ensuring utmost photocatalytic activity is explained based on numerical modeling of the heterostructures' formation using 'Unity' development platform. In addition, the heterostructures show photoluminescence. Its mechanism proposed here implies permeability of the materials' heterojunctions to electrons. This work describes new materials that can be used for photodegradation of organic pollutants. Besides, it extends available principles of design of photocatalytically active heterostructures.

The synthesis of novel heterojunction h-YbFeO3/o-YbFeO3 photocatalyst with enhanced Fenton-like activity under visible-light

A simple solution combustion approach followed by heat treatment was used to successfully synthesize a novel h-YbFeO₃/o-YbFeO₃ nanocrystalline heterojunction with an enhanced photo-Fenton-like activity in the decolorization process of methyl violet.

Mulberry-like BiVO4 architectures: synthesis, characterization and their application in photocatalysis

Mulberry-like BiVO₄ architectures were prepared by a facile solvothermal route. The obtained architectures showed enhanced light absorption, high photocatalytic properties, good stability and reusability.

A Z-scheme heterostructure constructed from ZnS nanospheres and Ni(OH)2 nanosheets to enhance the photocatalytic hydrogen evolution

ZnS and Ni(OH)₂ form a Z-scheme heterostructure, and the synergy between them provides a new hydrogen-producing active center for each material.

Bi and oxygen defects improved visible light photocatalysis with BiOBr nanosheets

Bi metal attached BiOBr with oxygen defect (BiOBr(3)-Bi(x%, x = 10, 20, 30)) nanosheets was prepared via the hydrothermal process in this study. The different characterization techniques of x-ray diffraction, x-ray photoelectron spectrometer, electron spin resonance (ESR), field emission scanning electron microscope, and high resolution transmission electron microscope were used to distinguish the composition, crystal structure, and morphology of the samples. Under visible light irradiation, the BiOBr(3)-Bi(x%, x = 10, 20, 30) samples exhibited improved photocatalytic activity for the degradation of colored dyes (RhB) and colorless tetracycline hydrochloride. Such an improvement was ascribed to the widened visible light absorption and enhanced separation of the photogenerated electron-hole pairs because of the synergistic effect of oxygen vacancies and Bi metal with plasmon resonance effects. A possible photocatalytic mechanism of the quasi Z-scheme process was proposed on the basis of ESR measurements and radical-trapping experiments.

Tunable Synthesis of Ultrathin BiOCl 2D Nanosheets for Efficient Photocatalytic Degradation of Carbamazepine upon Visible-Light Irradiation

A series of ultrathin BiOCl 2D nanosheet photocatalysts were prepared by the TBAOH-assisted hydrolysis method in water. The effects of tetrabutylammonium hydroxide (TBAOH) dosages, chlorine source, preparation pH value, ultrasonic treatment, and magnetic stirring on the photocatalytic degradation dynamics of carbamazepine were examined under visible-light irradiation to optimize the preparation parameters. It was found that ultrathin BiOCl prepared with TBAOH dosages of 1 mmol and chlorine source of NaCl in the pH of 2 upon magnetic stirring of 6 h displayed the highest photocatalytic degradation rate constant (0.0038 min−1) of carbamazepine, which is 7.6 times higher than that with the ordinary BiOCl (without TBAOH). To clarify the mechanism on the outstanding photocatalytic activity of ultrathin BiOCl, the elemental composition/state, micromorphology, and separation efficiency of photogenerated electron-hole pairs were investigated by X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), and photoluminescence (PL). Results showed that the presence of oxygen vacancy, ultrathin nanosheet structure, and improved separation efficiency of photogenerated electron-hole pairs contributed to the excellent photocatalytic degradation activity of ultrathin BiOCl. The obtained result provides a novel method to fabricate ultrathin BiOCl with excellent photocatalytic degradation activity of carbamazepine under visible-light irradiation.

Ultrasound-assisted synthesis of BiVO4/C-dots/g-C3N4Z-scheme heterojunction photocatalysts for degradation of minocycline hydrochloride and Rhodamine B: optimization and mechanism investigation

BiVO₄/C-Dots/g-C₃N₄Z-scheme photocatalyst with carbon dots as the electron mediators efficiently degrades minocycline hydrochloride and dye wastewater.