Photocatalytic Degradation Properties Research Articles

Enhanced photocatalytic degradation property of surfactant-free cobalt oxide nanocapsules on methylene blue dye

The transition metal oxides are emerging materials in solving existing environmental problems of removal of organic dye from the industrial wastes. Out of many transition metal oxides, cobalt oxide is one such potential material of low cost, easy to synthesis, eco-friendly and easily separable from mixtures due to its magnetic property. Herein a facile surfactant-free synthesis route has been adopted for the preparation of Co3O4 nanocapsules (Co 600) which exhibited a better photocatalytic degradation activity. The structure, morphology and optical behaviours were studied by using X-ray diffraction (XRD), scanning electron microscope (SEM), ultraviolet-visible spectroscopy (UV–vis) analyses respectively and vibration modes of Co 600 were studied using Raman analysis. The photocatalytic degradation studies of Co 600 on methylene blue (MB) were carried out under ultraviolet (UV) light irradiation. The examined results showed that the Co 600 exhibited narrow band gap of about 1.65 eV which has better photocatalytic degradation activity on MB with degradation efficiency of about 99% in 90 minute with a rate constant of about 0.064. This might be attributed due to enhanced charge separation, charge transfer and the creation of OH– and O2– radicals under UV irradiation. In addition, the samples were easily recovered from the dye solution using an external magnetic field.

Structural strategy to enhance the quantum and photocatalytic efficiency of ZnO quantum dots by incorporation of interface states

ZnO quantum dots (QDs) are potential candidates for high-efficiency emitters and photocatalysts. High efficiency demands high recombination of carriers, while high photocatalytic efficiency demands charge carrier separation. Here, we report an unexplored approach for achieving these opposite properties simultaneously by incorporating interface states in the ZnO QDs through a new strategy. We have used TEOS with Zinc acetate as synthesis precursors to prepare SiO2 encapsulated 5–6 nm ZnO QDs (ZnO@SiO2 QDs). X-ray photoelectron spectroscopy (XPS), FTIR and negative photoconductivity test confirmed the formation of interface states due to Zn − O − Si bonds between the SiO2 matrix and ZnO quantum dots. The ZnO@SiO2 QDs possess remarkable photocatalytic dye degradation properties, e.g., stability, efficiency and recyclability that outperform even the uncoated and commercially available ZnO beside high quantum yield varying between 46.1 % to 56.4 %, simultaneously. The photocatalytic mechanism has been further verified using the radical scavenger test. Thus, the work outlines designers' material design perspectives and discusses the detailed photophysical mechanisms for guiding the development of next-generation high-efficiency emitters and photocatalysts.

Photocatalytic degradation and electrochemical energy storage properties of CuO/SnO2 nanocomposites via the wet-chemical method

Integrating semiconducting functional materials is a way to enlarge the photoexcitation, energy range, and charge separation, greatly elongating the photocatalytic efficiency to enhance the chemical and physical properties of the materials. This work depicts and investigates the impact of cuprous oxide (CuO) and tin dioxide (SnO2)-based catalysts with various CuO concentrations on photocatalytic and supercapacitor applications. Moreover, three distinct composites were made with varied ratios of CuO (5, 10, and 15% wt. Are designated as AT-1, AT-2, and AT-3) with SnO2 to get an optimized performance. The photocatalytic properties indicate that the CuO/SnO2 nanocomposite outperformed its bulk equivalents in photocatalysis using Methyl blue (MB) dye in a photoreactor. The results were monitored using a UV–visible spectrometer. The AT-1 ratio nanocomposite displayed 96% photocatalytic degradation compared to pure SnO2 and CuO. CV analysis reveals a pseudocapacitive charge storage mechanism from 0.0 to 0.7 V in a potential window in an aqueous medium. The capacitive performance was also investigated for all electrodes, and we observed that a high capacitance of 260/155 F/g at 1/10 A/g was attained for the AT-1 electrode compared to others, specifying good rate performance.

Multifunctional porous nanofibrous membranes with superior antifouling properties for oil-water separation and photocatalytic degradation

The oily wastewater composed of complicated organic pollutants and bacteria showed a huge threat on the environment and humans. Currently, the membrane used to treat oily wastewater have the problems of cumbersome preparation, weak adhesion and metal leaching, and membrane pollution is also the focus of urgent problems. In this study, the metal-free chlorine-sulphur double-doped graphitic carbon nitride (Cl/S-g-C3N4) photocatalyst was incorporated into polyacrylonitrile (PAN) nanofibrous membrane via an electrospun method. The resultant porous nanofibrous membrane possessed the superior superhydrophilicity and superoleophobicity under water, ensuring a high separation efficiency (>98.0%) for various oil-in-water emulsions. Specially, the membrane achieved a superior self-cleaning property after visible light irradiation for crude oil/water mixture and actual oily wastewater with FRR up to 95%, which was related to the enhanced light absorption ability and the effective electron hole separation ability of Cl/S-g-C3N4. Moreover, the porous structure increased the possibility of contact between contaminants/bacteria and reactive species, beneficial to the photodegradation and antibacterial properties, achieving extremely high resistance to contamination. Overall, the multifunctionality of the porous anti-fouling nanofibrous membrane exhibited a huge potential in practical oily wastewater treatment.

Facile construction of 0D/2D In2O3/Bi2WO6 Z-scheme heterojunction with enhanced photocatalytic activity for antibiotics removal

Proper interfacial contact and efficient interfacial charge transfer play a predominant role in improving the photocatalytic performance. In this work, the 0D/2D In2O3/Bi2WO6 Z-scheme heterojunction was constructed successfully. The In2O3 nanoparticles were immobilized on the surface of the Bi2WO6 nanosheets via a facile hydrothermal-calcination method. The crystal structure and photoelectrochemical properties of samples were further characterized. 15% In2O3/Bi2WO6 (IB-15) exhibited optimal photocatalytic properties in degradation of tetracycline (TC) and oxytetracycline (OTC) under visible-light irradiation, and the possible degradation pathways of TC were acknowledged derived from LC-MS. According to the results of radical trapping experiments, superoxide radicals (•O2-) and photogenerated holes (h+) were predominant active species for TC degradation and a possible photocatalytic mechanism was proposed. The significant improvement of photocatalytic property was attributed to the unique Z-scheme heterojunction with 0D/2D architecture which facilitates the rapid separation of photo-excited carriers and expands the range of absorption spectrum.

Strong Photoelectric Properties of Mn‐Based Seleniumstannates with Alkali Metals as Structure‐Directing Agents

AbstractIn recent years, chalcogenides have received a lot of attention because of their potential applications as photoelectric material. This work describes the synthesis of the quaternary seleniumstannates Cs2MnSnSe4 (1) and Rb2MnSnSe4 (2) using solvothermal methods. The structure of compound 1 consists of charge‐balanced Cs+ cation and one‐dimensional (1D) anion [MnSnSe4]n2− chain. Compound 2 possesses a unique two‐dimensional (2D) anion [MnSnSe4]n2− layer. It is noteworthy that the compounds exhibit a strong photocurrent response (ca. 45 μA/cm2 (1), ca. 80 μA/cm2 (2)). Moreover, methylene blue (MB) was investigated for its photocatalytic degradation properties. In order to better understand the relationship between optical properties and electronic structure, a theoretical study was conducted.

Correction to: Photocatalytic Degradation Properties of SILAR Grown ZnO:Ag Thin Films: Investigation on the Effect of Ag Loading

Correction to: Photocatalytic Degradation Properties of SILAR Grown ZnO:Ag Thin Films: Investigation on the Effect of Ag Loading

Effect of Ni doping on the adsorption and visible light photocatalytic activity of ZnO hexagonal nanorods

Pristine and 1, 1.5, 2, 2.5 and 3 wt% Ni doped ZnO nanorods are prepared by hydrothermal technique as an effective photocatalyst for the removal of Malachite Green (MG) dye from aqueous media. Kinetic modelling of photocatalytic degradation and adsorption properties of the catalysts are done by pseudo first order (PFO), pseudo second order (PSO), fractal like psuedo first order (FPFO), fractal like psuedo second order (FPSO), elovich, exponential and intra particle diffusion (IPD) models. In contrary to the general trend, adsorption efficiency of ZnO is decreased while photocatalytic property got enhanced with doping. As-prepared catalysts are well characterised using XRD, FESEM, XPS, EDS, BET, UV and PL. This study points out the effect of Ni doping on the adsorption and visible light photocatalytic properties of ZnO nanostrutures via detailed kinetic modelling and explanation through various characterisation techniques and show cases their practical application in the field of waste water management. Water quality analysis was done post to degradation studies and the purified water samples have pH in the permissible range of drinking water which shows the efficient removal of dye molecules from the solution.

Piezoelectricity-enhanced photocatalytic degradation performance of SrBi4Ti4O15/Ag2O p-n heterojunction

Ferroelectric materials will generate an internal electric field when subjected to force, thus assisting to separate the photogenerated carriers. Here, a ferroelectric SrBi4Ti4O15/Ag2O p-n heterojunction catalyst is designed, inducing the remarkable enhancement of photocatalytic degradation performance by piezoelectric effect under the direct current electric field. The polarized SrBi4Ti4O15/Ag2O degrades 99.54 % Rhodamine B (RhB) within 6 min when exposed to light and ultrasonic vibration simultaneously, with an ultra-high degradation rate constant (k = 0.8949 min−1), which is 3.24 times of photocatalytic degradation rate (0.2765 min−1) and 17.38 times of the piezocatalytic degradation rate (0.0515 min−1). Moreover, SrBi4Ti4O15/Ag2O piezo-photocatalyst presents excellent degradation effect on methylene blue (MB), methyl violet (MV), methyl orange (MO) and tetracycline (TC). The piezoelectric effect induced by ultrasonic vibration provides a built-in electric field, which significantly enhances the separation of photoexcited carriers, consequently improving the photocatalytic degradation properties of SrBi4Ti4O15/Ag2O. This study provides a valuable reference for designing efficient photocatalysts by coupling photocatalysis and piezoelectric effect.

Flexible PAN-Bi2O2CO3–BiOI heterojunction nanofiber and the photocatalytic degradation property

In this paper, one-dimensional PAN-Bi2O2CO3–BiOI photocatalytic nanofibers were prepared using flexible PAN nanofibers as carriers. Bi2O2CO3 was first grown on the surface of PAN nanofibers, and then BiOI was loaded on Bi2O2CO3 by ion exchange method. The characterization results showed that PAN-Bi2O2CO3–BiOI nanofibers have a diameter of about 210 nm and regular fiber morphology. The results of UV–Vis diffuse reflectance spectroscopy, XRD and XPS showed that Bi2O2CO3–BiOI composed of granular semiconductor nano heterostructures with high specific surface area were uniformly loaded on the surface of PAN fiber. The photocatalytic degradation experiment of the material showed high visible light photocatalytic activity. The preparation of Bi2O2CO3–BiOI heterojunction improved the photoelectron hole separation efficiency of BiOI under visible light. PAN-Bi2O2CO3–BiOI fibers showed high photocatalytic degradation efficiency for rhodamine B. The degradation efficiency was more than 95% within 120 min irradiation. Free radical trapping experiments showed photocatalysts mainly produced O2−,·OH and h+, which played a major role in photocatalysis.

Comparative study on photocatalytic degradation and sensor properties of Chonemorpha fragrans leaf extract assisted MgxZn1−xO (0 ≤ x ≤ 1) nanoparticles

• Mg x Zn 1-x O (x = 0, 0.25, 0.5, 0.75 and 1) NPs were synthesized by Chonemorpha fragrans leaf extract assisted solution combustion method. • The photocatalytic degradation of Fast Blue (FB) and Malachite Green (MG) dyes were tested for all the samples. • MG dyes has higher (90%) degradation compared with FB (87% degradation) dye due to rise in the hydroxyl ions. • The low charge transfer resistance and high capacitance value of Mg x Zn 1-x O electrode were studied for all the samples. • The Nyquist plot is in the order MgO ˃ Zn 0.25 Mg 0.75 O ˃ Zn 0.50 Mg 0.50 O ˃ Zn 0.75 Mg 0.25 O ˃ ZnO. Chonemorpha fragrans leaf extract assisted solution combustion method was carried out for synthesizing Mg x Zn 1−x O (x = 0, 0.25, 0.5, 0.75 and 1) nanoparticles. The obtained samples were characterized using powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, and diffuse reflection spectroscopy techniques. The powder X-ray diffraction patterns of Mg x Zn 1−x O (x = 0 and 1) show pure hexagonal and cubic phases respectively and x = 0.25, 0.5, and 0.75 shows mixed phases. The Rietveld refinement study was done to refine structural parameters of × = 0, 0.5, and 1. A scanning electron microscope shows the high agglomeration with increasing ‘x’ content. Based on the Williamson-Hall plot, the average size of crystallites was found to be between 25 and 40 nm. Transmission electron microscope results also revealed the formation of nanoparticles. The energy bandgap was calculated from diffuse reflectance spectra using the Kubelka Munk relation and found to vary from 3.2 to 5.28 eV. The photocatalytic degradation of Fast Blue and Malachite Green dyes for all the Mg x Zn 1−x O nanoparticles catalysts was tested under the irradiation of UV light. Mg x Zn 1−x O nanoparticles showed enhanced degradation with increasing ‘x’ contents for Fast Blue (87%) and Malachite Green (90%) dyes under UV light. This enhanced degradation is due to variation in the bandgap of Mg x Zn 1−x O. Mg x Zn 1−x O electrodes exhibit a reversible electrode reaction based on their low charge transfer resistance and high capacitance value. Based on our results, the synthesized nanoparticles are promising candidates for wastewater treatment and lead sensor applications.

Photocatalytic activity of biogenic silver nanoparticles synthesized using Coleus Vettiveroids

• Simple, safe and eco-friendly synthesis of silver nanoparticles (AgNPs) using the leaf extract of Coleus Vettiveroids. • Study the influence of silver ion concentration on the size and properties of AgNPs. • AgNPs exhibited remarkable photocatalytic degradation properties in the reduction of organic dyes, methylene blue, malachite green, and crystal violet. In this work, simple, safe and eco-friendly synthesis of silver nanoparticles (AgNPs) using the leaf extract of Coleus Vettiveroids was carried out and it showed that the chemical species variations in this common family of plant extracts can have a different reducing ability of silver ions. The nanoparticles of silver were formed by the reduction, during UV exposure, of aqueous silver nitrate solution containing leaf extract of Coleus Vettiveroids . The AgNP formation was confirmed by the appearance of Surface Plasmon Resonance (SPR) band at ∼420 nm, which is characteristic for nano silver. The size of the prepared nanoparticles was characterised using Dynamic Light Scattering (DLS), average particle size was around 41.4 nm and for Transmission Electron Microscopy (TEM) the size was found to be ∼30 nm. The biogenic AgNPs found to have photocatalytic ability to degrade textile dyes such as crystal violet, methylene blue and malachite green. They exhibited excellent catalytic activity in the degradation of organic dyes within 3 hours of exposure time in presence of sunlight.

Two Polyoxometalate-Encapsulated Two-Fold Interpenetrating dia Metal-Organic Frameworks for the Detection, Discrimination, and Degradation of Phenolic Pollutants.

Phenols are widely used for commercial production, while they pose a hazard to the environment and human health. Thus, investigation of convenient and efficient methods for the detection, discrimination, and degradation of phenols becomes particularly important. Herein, two new polyoxometalate (POM)-based compounds, [Co2(btap)4(H2O)4][SiW12O40] (Co-POM) and [Ni2(btap)4(H2O)4][SiW12O40] (Ni-POM) (btap = 3,5-bis(triazol-1-yl)pyridine), are prepared via a hydrothermal synthesis method. The compounds show a fascinating structural feature of a POM-encapsulated twofold interpenetrating dia metal-organic framework. More importantly, besides the novel structures, the compound Co-POM realizes three functions, namely, the simultaneous detection, discrimination, and degradation of phenols. Specifically, Co-POM shows an excellent colorimetric detection performance toward phenol with a detection limit (LOD) ca. 1.32 μM, which is lower than most reported colorimetric detectors for phenol. Also, a new colorimetric sensor system based on Co-POM can discriminate phenol, 4-chlorophenol, and o-cresol with ease. Further, Co-POM exhibits a photocatalytic degradation property for 4-chlorophenol under irradiation of visible light with the highest degradation rate at 62% after irradiation for 5 h. Therefore, this work provides the first example of a POMs-based multifunctional material for achieving the detection, discrimination, and degradation of phenolic pollutants.

Eco-friendly fabrication of porphyrin@hyperbranched polyamide-amine@phytic acid/PVDF membrane for superior oil-water separation and dye degradation

The treatment of oily wastewater containing water-soluble dyes has drawn attention and become a thorny issue. Aiming at removing oil droplets and dyes from wastewater, it is reported in this work the design of polyelectrolyte deposited dual functional membrane with superior separation and degradation capabilities. The hyperbranched polyamide-amine (HPAMAM) was combined with tetra (4-carboxyphenyl) porphyrin (TCPP) and phytic acid (PA) through electrostatic interaction to form an eco-friendly polyelectrolyte complex by one-step self-assembly method. Relying on affluent amine group and unique cavity structure as well as wide range of delocalized π-electron systems, TCPP@HPAMAM@PA possesses robust water binding ability and intense absorption in the visible region, endowing PVDF membrane with superhydrophilicity/underwater superoleophobicity, oil resistance and superior photocatalytic degradation properties. The dual functional TCPP@HPAMAM@PA/PVDF membranes can realize superb removal of oil droplets (oil rejection > 99 %) at high flux recovery rate with several cycles. Furthermore, the degradation efficiency of rhodamine B (RhB) and Methyl blue (MB) reaches 93 % and 96 % respectively, showing standout photocatalytic degradation performance. A facile and low-energy strategy for the modification of commercial PVDF membranes is proposed, which is not only consistent with the concept of green chemistry but also has a broad application in the separation of complex oily wastewater systems.

Investigation of Cobalt Substitution on the Structural, Optical Band Gap, and Photocatalytic Dye Degradation Properties of Spray Deposited SnO2Thin Films

Pure and cobalt substituted tin oxide thin films are successfully formed on a glass substrate using the simple spray pyrolysis technique. XRD patterns reveal the polycrystalline nature of the samples with tetragonal rutile structure. The shift in X-ray diffraction peak to a higher 2θ value and its subsequent contraction of the SnO2 rutile lattice along the c-axis manifests the infusion of the guest cobalt ions. Crystallite size and microstrain values are found to vary with cobalt substitution. SEM analysis shows the uniform dispersion of the nanoparticles in the prepared thin films. The optical band gap values are found to narrow down with cobalt substitution from 4.04 eV–3.93 eV. Photoluminescence study hints at the presence of intermediate states within the forbidden energy band gap of SnO2. Photocatalytic dye degradation of Methylene blue (MB) highlights the role of cobalt with a high photocatalytic activity of 86 % compared to other investigated thin films.

COFs-Ph@CdS S-scheme heterojunctions with photocatalytic hydrogen evolution and efficient degradation properties

Combining the advantages of inorganic semiconductor and organic semiconductor is an effective way to construct heterojunction to improve the photocatalytic activity of materials. In this work, two covalent triazine framework (COFs-Ph)-based heterojunctions, which named hollow COFs-Ph@CdS and solid COFs-Ph@CdS, were synthesized by a facile hydrothermal method. And they were developed for the photocatalytic hydrogen evolution and efficient degradation for tetracycline (TC), 2,4-dichlorophenol (2,4-DCP), rhodamine B (RhB) under sunlight irradiation for the first time. Compared with solid COFs-Ph@CdS, hollow COFs-Ph@CdS catalysts exhibited a significantly enhanced activity for the photodegradation of various pollutants and photocatalytic hydrogen evolution. Under the simulated sunlight, the degradation rate of TC, 2,4-DCP, RhB by hollow COFs-Ph@CdS-3 was 87.2 %, 95.4 %, 82.6 %, respectively. The hydrogen production rate of hollow COFs-Ph@CdS-4 was 726 μmol·h−1·g−1. Based on the experimental results, it found that the interactions between CdS nanospheres and COFs-Ph could enhance the sunlight harvesting and created a new pathway to extend the service life of photogenerated charge carriers via facilitating the electron transfer through the loaded CdS nanospheres. Furthermore, the results verified that the matched band structure between COFs-Ph and hollow CdS could induce a superfast S-scheme interfacial charge transfer path. Therefore, a reasonable S-scheme charge transfer mechanism was proposed based on the active species trapping experiments and the results of electron spin resonance (ESR). More importantly, hollow COFs-Ph@CdS-3 possessed a good stability and reusability after recycling five times, that showed application prospect for solar-to-chemical energy conversion.

Cover picture: Production of mesoporous carbon nitrides and their photocatalytic properties for degradation of organic pollutants (BKCS 09/2022)

AbstractMesoporous C3N4 materials were produced through the self‐assembly of melamine and cyanuric acid. The materials showed excellent performance for degrading organic pollutants, rhodamine B, under the irradiation of visible light. Various study revealed that high surface areas, good adsorption ability of visible light, and long lifetimes of the photoexcited electrons would be origins for the photocatalytic superiority. More information can be found in the article by S. Park et al. image

Interface Nanoarchitectonics of TiO2/g-C3N4 2D/2D Heterostructures for Enhanced Antibiotic Degradation and Cr(VI) Reduction.

Mixed-phase TiO2 nanosheets were loaded on superior thin g-C3N4 nanosheets by a one-step solvothermal synthesis to form unique two-dimensional (2D)/2D heterostructures, which increased the interface area between TiO2 and g-C3N4, resulting in the easy migration of photogenerated carriers between two components. The rate of photocatalytic reactions increased significantly. Ciprofloxacin, tetracycline hydrochloride, and oxytetracycline hydrochloride were selected as target substances to test the photocatalytic degradation properties of the sample. The photoreduction performance of Cr(VI) was also tested. The results indicate that the photocatalytic degradation rate of antibiotics using TiO2/g-C3N4 heterostructures under visible light irradiation was twice that of g-C3N4. It took only 30 min to remove Cr(VI) (20 mg/L) under full solar spectrum irradiation; the photoreduction rate of Cr(VI) is also nearly twice that of pure TiO2. The improved performance was attributed to the rich active sites brought by mixed-phase TiO2 nanosheets. The extensive interface made the rapid migration of photogenerated carriers possible. The heterostructures revealed a band gap of 2.81 eV, which is less than that of TiO2 (3.2 eV), resulting in the increased absorption of visible light. Meanwhile, the mixed phase of TiO2 was beneficial for the separation of photogenerated carriers.

Leucas aspera mediated SeO nanoparticles synthesis for exploiting its pharmaceutical efficacy

The aim of this study is to synthesis Selenium oxide (SeO) nanoparticles using the leaf extract of Leucas aspera . The leaf extract has been reported to show phytochemicals effective for reducing Selenium precursors. Furthermore, these phytochemicals has being reported to show capping and stabilizing property. As-prepared nanoparticles physico-chemical properties were assessed by a array of various characterization technique. UV-Vis and XRD assessment showed maximum absorbance at 273 nm with high crystalline property. Qualitative assessment using FTIR assessment was performed to assess the phytochemical based functional groups presence which helped in reducing, stabilizing of the prepared nanoparticles. Morphological assessment of nanoparticles showed spherical attributes with good aggregation. Functional attributes of SeO nanoparticles for exploiting its pharmaceutical application, illustrated a significant antibacterial activity against both gram negative and gram-positive strains comparable to commercially available antibiotics. Moreover, MTT assay was employed to assess anticancer behaviour of SeO nanoparticles towards MG-63 cells, which showed effective reduction in cell viability. Furthermore, the study confirms photo catalytic degradation property of SeO nanoparticles towards dye degradation. The study not only discusses the SeO nanoparticles physico-chemical and functional properties, but and also opens future scope of SeO in clinical and environmental applications. • Prepared SeO nanoparticles from Leucas aspera stem extract by green synthesis. • Enhanced structural, dye degradation and antibacterial activity. • MTT assay method is used for the analysis of the anticancer activity of SeO.

Facile synthesis of N-doped TiO2 and its photocatalytic properties for ciprofloxacin degradation

The preparation of N-doped TiO2 with excellent photocatalytic performance is reported. The study of the synthesis process involves the control of N-doping and the crystalline phase. The incorporation of urea provides dual features; it introduces a nitrogen source and also reduces the phase transition temperature of anatase to rutile. The optimal N-doped catalyst that possesses both anatase and rutile phases shows excellent catalytic efficiency in the degradation of ciprofloxacin under illumination by visible light and sunlight.