Photocatalytic Degradation Performance Research Articles

NGO/ZnO2/ZnO heterojunctions with self-accelerating photocatalysis for efficient degradation of organic dyes

Photocatalytic degradation of dyes using semiconductor materials has received widely attention. We employed ZnO2 as a zinc source and synthesized NGO/ZnO2/ZnO heterojunctions with self-accelerated photocatalytic function by hydrothermal technique and investigated their photocatalytic degradation performance of RhB and MO under simulated sunlight irradiation. NGO greatly improved the adsorption performance of NGO/ZnO2/ZnO on dyes, among which, the adsorption of MO dyes was 11 times higher than that of ZnO2/ZnO. While enhancing the sunlight absorption range and adsorption performance, the NGO could also rapidly transfer electrons and effectively inhibit the complexation of electron-hole pairs, further improving the photocatalytic performance. By optimizing the doping ratio of NGO, NGO/ZnO2/ZnO with the highest photocatalytic degradation activity was obtained, which was 4.4 times higher than that of ZnO2/ZnO. In addition, the acid-base resistance and cycling experiments showed that the NGO/ZnO2/ZnO-3 photocatalyst had good stability. The EPR experiments showed that ·O2− and ·OH radicals were extremely important active substances in the whole photodegradation process. Finally, the synergistic enhancement mechanism of the photocatalytic performance of ZnO by NGO and ZnO2 was revealed. This work provides a good strategy for designing ZnO composite photocatalysts to efficiently degrade organic dyes.

Zn2SnO4/SnO2/g-C3N4 heterojunction: High efficiency photocatalytic degradation of Rhodamine B in simulated visible light

Photocatalysis is an effective solution to wastewater treatment problems, and semiconductor heterojunctions for photocatalysis can effectively separate photogenerated carriers to improve the performance of photocatalytic degradation of pollutants. In this paper, a ternary composite photocatalyst with a heterojunction structure (Zn2SnO4/SnO2/g-C3N4) was prepared to photodegradeRhodamine B in simulated visible light. The experimental findings demonstrate that the Zn2SnO4/SnO2/g-C3N4 photodegradation rates and efficiencies for RhB are much higher than those for SnO2, g-C3N4, SnO2/g-C3N4, and Zn2SnO4/SnO2. We obtained a 3:1 mass ratio of Zn2SnO4/SnO2 to g-C3N4 by optimization, with a maximum degradation rate of 99.5 % and a maximum kinetic constant k of 0.692 min-1·g−1 for the photocatalytic removal of RhB by Zn2SnO4/SnO2/g-C3N4. The radical trapping experiments suggest the primary role of ·O2– for the photocatalytic removal of RhB. The ternary composite photocatalyst Zn2SnO4/SnO2/g-C3N4 shows promise for potential applications in RhB degradation owing to its exceptionally.

Photoinduced RhB-sensitized effect on a novel AgI/BiOCl/biochar photocatalyst to boost its photocatalytic performance for 17α-ethinyl estradiol degradation

In this study, a simple and effective strategy was developed for the synthesis of novel visible-light-active AgI/BiOCl/biochar (AgI/BiOCl/BC) photocatalysts. The addition of rhodamine B (RhB) as a sensitizer was found to considerably enhance the photocatalytic activity of AgI/BiOCl/BC toward the degradation of 17α-ethinyl estradiol (EE2). Furthermore, the incorporation of biochar (BC) into the BiOCl resulted in an increased abundance of free radicals, that could be used for degradation. Additionally, the presence of BC facilitated the separation of carriers by serving as an electron transport channel. The photocatalytic efficiency of the AgI/BiOCl/BC photocatalyst was shown to be highly effective in the degradation of EE2, the degradation efficiency of the AgI/BiOCl/BC was found to be 98.60 % after a 12-min exposure to visible light. Additionally, the photocatalytic activity increased further when RhB sensitization was performed, resulting in a remarkable elimination efficiency of 99.60 % for EE2 after only 4 min of photocatalysis. RhB could not only provide photosensitivity but also degrade along with EE2 as a pollutant, which can be used for the treatments of dyes and EE2 wastewater. The results of photocatalysis investigations indicated that AgI/BiOCl/BC could degrade various dyes, including methyl orange (MO), methylene blue (MB), and congo red (CR). Through the introduction of Ag-based materials, the obtained AgI/BiOCl/BC photocatalyst exhibited significant antibacterial potential against Staphylococcus aureus and Escherichia coli, with antibacterial rates of 99.94 % and 99.99 %, respectively. The cyclic experiment demonstarted that AgI/BiOCl/BC exhibited excellent stability and recyclability. Furthermore, the potential photocatalytic mechanism and degradation pathway were suggested through a combination of experimental findings and theoretical investigations. The obtained AgI/BiOCl/BC photocatalyst is a multifunctional photocatalyst with excellent performance in photocatalytic degradation and sterilization. This photocatalyst is expected to be applied to the treatment of complex pollutant water in the environmental field.

Facile synthesis of Ag2CO3/Ag2O@NiFe LDH nanohetrostructure with enhanced photocatalytic performance for MB dye degradation under visible light irradiation

The photocatalyst Ag2CO3/Ag2O@NiFe LDH nanocomposite was synthesized successfully by a facile co-precipitation method followed by hydrothermal treatment. The as-prepared photocatalyst demonstrated excellent physicochemical and optical properties using various characterization techniques. It was found that the photodegradation performance of NiFe LDH for MB dye removal can be significantly improved by appropriate Ag incorporation. The optimal composite which had a 0.75 Ag molar ratio demonstrated superior degradation performance for MB dye reaching 99.5%. The degradation efficiency was three times higher compared to pure NiFe LDH. Additionally, the apparent rate constant (0.028 min−1) was approximately 28 times greater than that of the pure LDH (0.001 min−1). After 5 successive cycles, the composite exhibited 73% degradation efficiency reflecting its high photostability throughout the regeneration process. The synthesized photocatalyst exhibited exceptional properties, indicating its promising potential for industrial applications in the treatment of dye wastewater.

Synthesis of ZnO-Cdots nanoflower by hydrothermal method for antibacterial agent and dye photodegradation catalyst

Implementing nanosized materials (1–100 nm) are considered to be effective approaches in addressing the issue of liquid waste pollution. Herein, ZnO-carbon quantum dots (ZnO-Cdots) were conducted by three-steps hydrothermal synthesis and the structural characterization is confirmed by the physical properties measurement, while, photodegradation activity of ZnO-Cdots compared to the prepared ZnO nanoflower has been investigated using UV–visible absorbance spectroscopy and its effect on organic pollutant removal from aqueous. The obtained ZnO-Cdots composites showed a superior performance in photocatalytic degradation of methylene blue (MB) and specific antibacterial activity against Staphylococcus aureus (S.A) and Eschericia coli (E.coli) compared to the prepared ZnO nanoflower. The findings of this research of ZnO-Cdots show great potential in treating liquid waste pollution, and can be considered as a promising antibacterial agent for Staphylococcus aureus (S.A) and Eschericia coli (E.coli).

Enhanced photocatalytic degradation performance of layered Ag-Bi4Ti3O12 plasmon resonance-coupled piezoelectric effect

Piezoelectric effects in ferroelectric materials arise from generating an internal electric field when subjected to mechanical stress, greatly facilitating the separation of photo-generated charge carriers in photocatalytic processes. However, it faces limitations such as inadequate conductivity and a restricted number of active sites. In this study, we successfully synthesized Ag-Bi4Ti3O12(Ag-BTO) composite piezoelectric photocatalysts using a molten salt method. By harnessing the synergistic combination of the piezoelectric effect and localized surface plasmon resonance, we achieved enhanced efficiency in photocatalytic processes. Optimizing the loading ratio of Ag, we achieved complete degradation of Rhodamine B (RhB) within a concise duration of 6 min, with degradation rates 1.867 times and 5.907 times higher than those observed for pure photocatalysis and piezoelectric catalysis, respectively. This research provides an illustrative approach for natural light and different piezoelectric driving forces for environmental remediation and imparts valuable insights for the design of highly efficient piezoelectric photocatalysts.

Photocatalytic Performance and Degradation Pathways of Z‐Scheme BiO2−X−Ag3PO4 Photocatalysts with Oxygen‐Deficient Structures

AbstractIt is a practical way to raise the efficiency of photocatalysis by using oxygen vacancy defect modified materials. In this experiment, a Z‐scheme BOA composite photocatalyst with defect structure was prepared by hydrothermal in situ precipitation method. The optimal ratio of 1.5 BOA showed excellent photocatalytic degradation performance for MO, TC and CIP under visible light irradiation, and maintained good structural stability and circulation rate after five cycles. The increased photocatalytic activity of the composite can be explained to the heterojunction interface‘s synergistic effects and the quicker electron hole transit rate caused by the surface oxygen vacancy defect. XPS and EPR confirmed the existence of anoxic structure in the composite, PL and photocurrent confirmed the high electron hole transfer rate. The active species that contributed to the degradation process were validated by the active species capture experiment and ESR. LC–MS speculated the possible degradation path of CIP. Finally speculated the reaction mechanism of Z‐scheme BOA composite photocatalyst. Using the anoxic structure of BiO2−X to form a Z‐scheme heterostructure with Ag3PO4, the oxygen vacancy as the electron capture center and active site is conducive to improving the photogenerated electron transfer rate, thereby improving the structural stability and photocatalytic performance of the complex.

Defective UiO-66 by metal doping for highly efficient photocatalytic degradation of methyl mercaptan

Defective UiO-66 by metal doping exhibits considerable promise in the photocatalytic degradation of environmental contaminants, albeit how different metal doping affect formation of defects and its efficacy in the degradation of methyl mercaptan has yet to be comprehensively explored. In this study, a one-step solvothermal method was employed to successfully synthesize six distinct metal-doped UiO-66 with variations of defects by incorporating Ce, Al, Cu, Cr, Mg, and Fe. A systematic examination of the structural and photochemical attributes of these metal-doped UiO-66 materials was conducted through a series of characterisations. Metal doping creates defects in UiO-66, changes its colour and morphology and increases its specific surface area. Subsequently, the adsorption and photocatalytic degradation characteristics of these nanomaterials concerning methyl mercaptan were investigated. In comparison to pristine UiO-66, all metal-doped UiO-66 variants exhibited enhanced adsorption and photocatalytic degradation capabilities towards methyl mercaptan. Notably, among the prepared materials, FeUiO-66 demonstrated the most exceptional photocatalytic degradation performance, followed by CuUiO-66, AlUiO-66, CeUiO-66, CrUiO-66, and MgUiO-66 in that order. 1.0FeUiO-66 exhibiting the most remarkable performance, achieving a 99 % degradation of methyl mercaptan within 30 min. This represented a degradation rate 36.8 times higher than that of pure UiO-66, attributable to the incorporation of low-valence metals into the UiO-66 framework, resulting in the creation of oxygen vacancy defects. Furthermore, the presence of these metals facilitated electron transport, thereby enhancing the efficiency of photocatalytic degradation. This study underscores the potential of various metals-doped UiO-66 for adsorption and photocatalytic elimination of methyl mercaptan.

Synthesis of diverse titanium dioxide (TiO2) nanostructures for enhanced photocatalytic degradation and supercapacitor performance

Synthesis of diverse titanium dioxide (TiO2) nanostructures for enhanced photocatalytic degradation and supercapacitor performance

Preparation of rose-like Bi2O2CO3 photocatalyst with enhanced performance for photocatalytic degradation of mineral flotation wastewater

Eight kinds of bismuth oxycarbonate (Bi2O2CO3, BOC) with different microscopic morphology were prepared to study the influence of microscopic morphology on its photocatalytic performance. The crystal structure and microscopic morphology of Bi2O2CO3 were regulated by different synthetic recipes and routes. The SEM and TEM show the samples can be classified into two-dimensional (2D) and three-dimensional (3D) Bi2O2CO3 materials. The BOC-8 possesses a rose-like structure and a specific surface area (SBET) of 44.93 m2/g. In the experiments of degrading mineral flotation agent sodium isobutyl xanthate (SIBX). The photocatalytic performance of 3D samples is generally superior to that of 2D samples, and BOC-8 exhibits the best photocatalytic performance. After 90 min of simulated sunlight irradiation, the degradation ratio of SIBX over BOC-8 is 92.41 %. The transient photocurrent-time curves, electrochemical impedance spectroscopy (EIS) and photoluminescence (PL) spectra show that BOC-8 has excellent photogenerated electron and hole separation efficiency. The degradation pathway of SIBX was explored. And the hydroxyl radicals (OH) is the main active oxygen species for SIBX degrading. The enhanced photocatalytic degradation performance of BOC-8 samples originated from the increase of SBET, improved light utilization and more efficient photogenerated charge separation caused by the formation of 3D structure.

Fabrication of oxygen-rich vacant 3D Zn–CuBi2O4/MMT photocatalysts and the enhancement of its photocatalytic performance

Semiconductor catalytic materials have excellent photocatalytic degradation performance for organic pollutants, and photocatalytic degradation is considered to be the most promising technology for environmental pollution treatment. Bismuth-based bimetallic oxide CuBi2O4 is widely recognized as one of the most valuable and promising semiconductor photocatalytic materials because of its narrow bandwidth, strong visible light absorption and excellent chemical stability. To further improve the photocatalytic activity of CuBi2O4, the Zn-doped CuBi2O4/montmorillonite composites were prepared by employing a synergistic control strategy of doping and oxygen vacancies (OVs), which efficiently regulated the electronic structure and the number of active sites to achieve a rapid separation of photogenerated charges. The doping of zn2+ significantly increased the quantity of oxygen vacancies in the prepared materials. The BET revealed that the incorporation of montmorillonite (MMT) greatly increased the specific surface area of CuBi2O4. The experimental findings indicated that 5 % Zn–CuBi2O4/MMT0.6 possessed abundant oxygen vacancies and longer fluorescence lifetime, resulting in better photocatalytic performance. The removal rate of butyl xanthate was 99.31 % in 40 min, and the removal rate of tetracycline hydrochloride (TC) was 93.17 % in 180 min. The 5 % Zn–CuBi2O4/MMT0.6 could effectively inhibit e−/h+ complexation and provide richer catalytic active sites by doping to construct a flower-like oxygen-rich vacancy defect structure, which significantly improves its catalytic performance. The results of the cycling experiments showed that the stability and reproducibility of the 5 % Zn–CuBi2O4/MMT0.6 composites were excellent, the present study provides an innovative idea for the development of efficient and stable visible light photocatalytic applications.

Photocatalytic degradation performance of antibiotics by WO3/α-Fe2O3/zeolite type II heterojunction with core-shell structure.

The accumulation of antibiotics in the environment can be harmful to human health, and research on their disposal technologies is of increasing interest. In this study, WO3/α-Fe2O3/zeolite (WFZ) type II heterojunction composites with core-shell structures were prepared by coupling WO3 semiconductors with visible-light photocatalytic activity with α-Fe2O3 via hydrothermal synthesis using zeolite as a carrier for the adsorption of synergistic photocatalytic degradation of antibiotics in wastewater. X-ray diffraction, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), specific surface, and porosity measurements were used to characterize the structure of WFZ type II heterojunction. The performance of WFZ heterojunction for the visible photocatalytic degradation of antibiotics (tetracycline hydrochloride (TCH), ciprofloxacin (CIP), and levofloxacin hydrochloride (LVF)) was investigated. Through four photocatalytic cycles, the catalyst exhibited excellent durability and stability. This was attributed to the core-shell structure and type II heterojunction promoting the effective separation of photogenerated carriers and the extended visible light response range, which resulted in the best photocatalytic activity of the catalyst under visible light irradiation. Radical trapping experiments showed that superoxide radicals (•O2-) and hydroxyl radical (•OH) were the main active species that played a major role in the photocatalytic degradation. These findings show that the synthesized WFZ type-II heterojunction can be used as a reliable visible-light-responsive photocatalyst for the treatment of antibiotics in wastewater.

Unveiling the synergistic interplay of appropriate oxygen vacancies and S-scheme heterojunction structures in OVs-TiO2/g-C3N4 catalyst for efficient RhB photodegradation and H2 production

This study presents a facile synthesis for an efficient S-scheme OVs-TiO2/g-C3N4 heterojunction (OVs-TCN) enriched with oxygen vacancies, demonstrating exceptional performance in photocatalytic RhB degradation and H2 production. Controlled introduction of g-C3N4 into OVs-TiO2 modulates appropriate oxygen vacancies within the OVs-TCN10 heterojunction. Under visible irradiation, OVs-TCN10 achieves a remarkable 97.2 % degradation of RhB over 120 min with 5 cycles, with an apparent rate constant of 0.021 min−1. Impressively, OVs-TCN10 exhibits significant H2 production from RhB degradation, reaching a rate of 150 µmol h−1 under visible irradiation for 30 h, with a 15 % AQY at 420 nm. Experimental and DFT analyses of charge density difference, along with Mulliken analysis at the OVs-TiO2/g-C3N4 interface, confirm the existence of an intrinsic electric field flowing from g-C3N4 to OVs-TiO2. This internal electric field enhances photogenerated electron-hole separation and transfer, facilitating the redox process via the S-scheme mechanism in the heterojunction for photocatalytic RhB degradation and H2 production. This work offers new insights into the controlled defects and interfacial mechanisms in heterojunctions, propelling advanced photocatalytic applications.

A two-fold interpenetrated Zn(II) organic framework based on mixed ligands: Synthesis, crystal structure, and properties

A new zinc(II) metal organic framework has been obtained from the solvothermal assembly of 1,3,5-benzene tricarboxylate and 1,3-bis(imidazole)propane with zinc nitrate in DMAc–H2O (DMAc is N,N-dimethylacetamide), namely {[Zn2 (μ2-OH)(1,3-BIP)(BTC)]·DMAc·2H2O}n (SNUT-6). The product is characterized by single-crystal and powder X-ray diffraction, infrared spectroscopy, thermogravimetric analysis, and elemental analysis. The single-crystal X-ray diffraction reveals that SNUT-6 exhibits a 3D→3D two-fold interpenetrating framework. Furthermore, SNUT-6 demonstrates a highly efficient turn-off fluorescent detection ability for aniline in methanol and shows high sensitivity with a Ksv value of 4.771 × 104 M−1. It also shows excellent photocatalytic degradation performance for a three-dye molecular model: rhodamine b, methyl orange, and methyl blue.

Hydrothermal synthesis of Bi2WO6/Bi2O4 heterojunction with WO3 and NaBiO3·2 H2O powders as precursors to improve visible light photocatalytic degradation performance

The limited visible light response range and fast recombination rate of photoinduced carriers restrict the photocatalytic performance of Bi2WO6. Herein, a novel low temperature hydrothermal approach was developed to construct the Bi2WO6/Bi2O4 heterojunction with WO3 and NaBiO3•2 H2O powders as precursors and the latter as the only bismuth source. During the hydrothermal reaction, WO3 first reacts with NaBiO3·2 H2O to generate Bi2WO6 and then the residual NaBiO3·2 H2O converts into Bi2O4, in-situ forming the Bi2WO6/Bi2O4 heterojunction with the co-shared Bi atoms. The content of Bi2WO6 in the heterostructure can be facilely modulated by changing the amount of WO3 added. The construction of Bi2WO6/Bi2O4 heterojunction could not only extend the spectral response range but also improve the separation efficiency of photoinduced charges. Consequently, the photocatalytic degradation performance to tetracycline (phenol) for the optimal Bi2WO6/Bi2O4 heterostructure is 5.19 and 1.77 times (4.75 and 1.66 times) higher than that of single Bi2WO6 and Bi2O4 under visible light, respectively. The capture experiments of active species and electron spin resonance spectra demonstrate that radicals (·O2-) and holes (h+) are the first and second important active species, respectively, during the catalytic degradation. Our work provides a new idea for the fabrication of high-performance Bi2WO6-based junction photocatalysts.

Templated synthesis of ZnO quantum dots via double solvents method inside MOF-801 as emerging photocatalyst for photodegradation of Acid Blue 25 under UV light

Templated synthesis of ZnO quantum dots (QDs) is one of the most important techniques for controlled synthesis of it without need of surfactants and advanced laboratory equipment. MOF-801 was used as a template for the synthesis of ZnO QDs with controlled shape and size. The “ship-in-a-bottle” approach was applied for templated synthesis of ZnO QDs into the MOF-801 porous matrix via double solvents method (DSM) combined with an in situ reduction route (ISRR). The formation of ZnO QDs inside MOF-801 template was monitored by PXRD, FT-IR, EDX, ICP-OES, XPS, BET, TEM, DRS, PL, EIS, and Mott − Schottky analyses. The ZnOQDs@MOF-801 nanocomposite as emerging photocatalyst exhibited better photocatalytic performance for degradation of Acid Blue 25 with a rate constant of 0.00179 min−1 which is 2.35 higher than MOF-801 (0.00076 min−1) under UV irradiation, due to ZnO QDs embedded inside MOF-801 template. The unique properties of ZnO QDs, including quantum confinement, multiple exciton generation, and efficient separation of charge carriers through decrease in electron-hole recombination at the quantum scale, contribute to the photocatalytic degradation of Acid Blue 25.

Surface plasmon resonance Bismuth-modified NH2-UiO-66 with enhanced photocatalytic tetracycline degradation performance

For nearly a century, the misuse of antibiotics has gradually polluted water and threatened human health. Photocatalysis is considered an efficient way to remove antibiotics from water. Zirconium-based metal–organic frameworks have attracted much attention as promising photocatalysts for the degradation of antibiotics. However, single Zirconium-based metal–organic frameworks can still not achieve a more satisfactory photocatalytic efficiency, due to poor light absorption and charge separation efficiency. In this study, a novel metal-loaded metal–organic frameworks material was explored. As a potential photocatalytic material, the performance of NH2-UiO-66 in the photocatalytic degradation of tetracycline was greatly improved just by the loading of a single metal. Bismuth/NH2-UiO-66 photocatalysts of various compositions were physicochemically (TEM, SEM, XRD, XPS, BET, FTIR, UV–VIS, PL), and electrochemically (electrochemical impedance spectroscopy, photocurrent response) characterized. We evaluated the photocatalytic performance of Bismuth/NH2-UiO-66 composites by measuring their ability towards tetracycline decomposition in simulated sunlight irradiation conditions. The experimental results indicated that the introduction of metal Bismuth significantly boosts the photocatalytic activity of the composite catalysts. The final degradation rate of Bismuth/NH2-UiO-66 for tetracycline was found to be 95.8%, namely 2.7 times higher than pure NH2-UiO-66. This behavior is due to the surface plasmon resonance effect of Bismuth, which ameliorates the photocatalyst's electron-hole separation and strengthens the charge transfer. Apart from that, the presence of Bismuth magnifies the visible-light absorption range of Bismuth/NH2-UiO-66. In this study, an innovative approach for designing efficient and cost-effective metal-modified metal–organic frameworks photocatalysts is proposed.

Dynamic properties of photogenerated charge in BiOBr/Bi2WO6/GO ternary composites and its application for organic pollutants degradation.

Carbon-based Materials have been extensively researched for their prospect in the fields of environment and energy, especially for graphene oxide (GO). In this work, a novel sodium dodecyl sulfate (SDS)-assisted synthesis of BiOBr/Bi2WO6/GO ternary composite has been synthesized successfully by a handy hydrothermal method. Photoluminescence, Photocurrent, Electrochemical Impedance Spectroscopy, surface photovoltage and transient photovoltage measurements illustrate that construction of p-n BiOBr/Bi2WO6 heterojunction leads to the obviously enhancement of charge separation efficiency, and the photogenerated electrons trapped by GO can effectively inhibit the recombination process of photogenerated charge, resulting in the improvement of charge separation efficiency and the longer lifetime of photogenerated carriers for BiOBr/Bi2WO6/GO. The characterization of structure and morphology indicate that role of GO can also improve the visible light absorption range, and the SDS-assisted synthesis can reduce the size of particle in the composite and enhances the specific surface area of the composite by regulating the particle size and agglomeration. Under optimal conditions, BiOBr/Bi2WO6/GO (SDS) has the outstanding photocatalytic degradation performance and the degradation rate constants for oxytetracycline, tetracycline hydrochloride, methylene blue and rhodamine are 0.056, 0.057, 0.103 and 0.414min-1, respectively. Notably, the degradation rate constants obtained by BiOBr/Bi2WO6/GO (SDS) are more ten times higher than that of pure BiOBr and Bi2WO6. The possible mechanism of photocatalytic degradation was suggested for BiOBr/Bi2WO6/GO based on the dynamic properties of photogenerated charge and reactive oxidation species results. Surprisingly, the recyclability of the BiOBr/Bi2WO6/GO (SDS) composite obtained from the cyclic experiments has laid a foundation for the study of efficient and stable photocatalysts.

Interface engineering of a magnetic 2D-C3N4/Fe2O3/NiFe-LDH heterostructure for efficient photocatalytic degradation of methylene blue and rhodamine B dyes under visible light

Double layer hydroxide (LDH) as a photocatalyst has potential features in water pollution control. In the present study, the iron (III) oxide /two-dimensional carbon nitride/nickel‑iron LDH (Fe2O3/2D-C3N4/NiFe-LDH) composite was synthesized by pyrolysis and co-precipitation process from waste iron rusts as one of the cheap precursors along with NiFe-LDH and g-C3N4. The photocatalytic activities of magnetic Fe2O3/2D-C3N4/NiFe-LDH as stable photocatalyst for degradation of methylene blue (MB) and rhodamine B (RhB) as cationic dyes was studied and then the characteristics of the resulting materials, including morphology, structure, crystal phase, optical and electronic properties, were clearly investigated using different techniques. The fabricated Fe2O3/2D-C3N4/NiFe-LDH provide greatly improved photocatalytic performance for dye degradation compared to the sole Fe2O3 and Fe2O3/g-C3N4.The maximum elimination efficiency of MB and RhB are 91.2% and 88.5% respectively. 80% COD photodegradation was achieved under optimal conditions including catalyst loading (0.36 g/L), initial pH (9.0), LED irradiation time (60 min), and initial concentration of MB (10 mg/L) and RhB (9 mg/L). The obtained photocatalyst was effectively recovered using an applied magnetic field. Based on the reusability study, the fabricated photocatalyst was chemically stable and corrosion resistant.

S-scheme heterojunctions based on novel Sm2CeMnO6 double perovskite oxide and g-C3N4 with excellent photocatalytic dye degradation performances.

It has become of utmost importance to preserve marine life and human health by protecting aquatic environments from contaminants. Therefore, using photocatalytic materials in treatment of contaminated water is a promising and innovative technique. Novel double perovskite Sm2CeMnO6 was synthesized through a modified Pechini sol-gel method. Also, urea and melamine were utilized to synthesize graphitic carbon nitride (g-C3N4). Combination of Sm2CeMnO6 and g-C3N4 produced several S-scheme heterojunction materials in diverse components ratios. Average crystallite sizes of Sm2CeMnO6 and Sm2CeMnO6/g-C3N4 (20:80) samples were calculated by Debye-Scherrer and Williamson-Hall methods to be 19.77, 22.72 nm and 42.01, 43.73 nm, respectively. The coexistence of g-C3N4 (002) with a d-spacing of 0.325 nm and Sm2CeMnO6 planes of (222), (111), and (400) with spacing values of 0.314, 0.302, and 0.294 nm, respectively, was depicted in the HR-TEM image of the Sm2CeMnO6/g-C3N4 (20:80). The estimated bandgaps for the g-C3N4, Sm2CeMnO6, and Sm2CeMnO6/g-C3N4 (20:80) were 2.70, 2.60, and 2.65eV, respectively. Their application was investigated in photocatalytic degradation of methylene blue (MB) dye as typical pollutant. The estimated degradation pathway of MB was also provided through LC-MS analysis. Under the identical conditions, the best photocatalytic performance was found for Sm2CeMnO6/g-C3N4 (20:80) composite. Using response surface methodology (RSM), operational parameters of the photocatalytic degradation were modeled and optimized by the best composite through central composite design approach. Applying optimized parameters led to 96% degradation of MB (8 mg/L) at pH 10 under 120 min visible light irradiation (λ > 365 nm) using 0.15 g of Sm2CeMnO6/g-C3N4 (20:80) composite in 100 mL aqueous solution. Due to low intrinsic charge transfer resistance, modified Eg, and good performance in e‒/h+ pairs production, Sm2CeMnO6/g-C3N4 (20:80) nanocomposite was introduced as a promising S-scheme photocatalyst.