Photocatalytic Activity Of Composites Research Articles

Synthesis of SnO2/SrTiO3 composite and photocatalytic activity for methylene blue degradation under sunlight

In this study, the SnO2/SrTiO3 composite has been fabricated by, firstly preparing SnO2 and SrTiO3 through, followed by coupling SnO2 and SrTiO3 by the hydrothermal method at 180 oC for 24 hours. The obtained materials were characterized by X-Ray diffraction (XRD), Fourier transformation infrared spectra (FT-IR), energy-dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM). The photocatalytic activity of composite was assessed by degradation of methylene blue in water under sunlight. The composite exhibits a good photocatalytic activity compared to individual components (SnO2 and SrTiO3). An enhancement in photocatalytic activity of the composite with the presence of SnO2 has been observed. 1,4-benzoquinone (BQ) và tert-butyl alcohol (TBA) were used as quenchers for trapping photogenerated superoxide radical anions (•O2-) and hydroxyl radicals (•OH), respectively. In the presence of the quenchers, the photocatalytic activity of the composite has decreased significantly.

NiFe2O4/ZnO nanocomposites for degradation of MB dye with their local electrical behavior

In the present work NiFe2O4/ZnO nanocomposites were successfully prepared by in-situ wet chemical co-precipitation process. XRD study reveals the presence of the cubic structure of NiFe2O4 and wurtzite hexagonal structure of ZnO. FTIR reveals the distribution of cations and anions at different interstitials sites. Further, the morphology of synthesized sample is analyzed by use of TEM. The oxidation state was explained from X-ray photoelectron spectroscopy (XPS). Dielectric constant is calculated from impedance spectroscopy. UV–vis spectroscopy was used to evaluate the band gap (1.68eV-3.2 eV) of the materials by Tauc's plot. As a model contaminant methylene blue (MB) dye used to check the performance and (0.5) NiFe2O4 - (0.5) ZnO sample shows the maximum degradation efficiency which is 91.36%. The photocatalytic activity of composites is found to be better than bare materials.

Facile synthesis of graphene quantum dots/ZSM-5 type metalosilicate composites and evaluating their performance in photocatalytic degradation of methylene blue and electrochemical water splitting

Graphene quantum dots (GQDs)/ZSM-5 type cobaltosilicate and GQDs/ZSM-5 type chromosilicate composites were prepared by two methods; direct and solid state dispersion (SSD) method. The composites were characterized using XRD, FT-IR, UV–vis absorption, and SEM techniques. The photocatalytic activities of composites were evaluated by degradation of methylene blue (MB) under both UV and vis light irradiation. The composites prepared by direct method showed better photocatalytic activity and the GQDs/chromosilicate composite had a superior performance. This composite could remove about 96 % and 87 % of MB at first 30 min under UV and vis light, respectively. The results of photocatalytic degradation kinetic studies revealed that the composites follow the pseudo-second-order kinetic model (R2 = 0.99) with rate constants ranging from 0.295 to 0.581 g mg−1 min−1 for different composites prepared by direct method. The GQDs/metalosilicate composites were also examined for the electrochemical water splitting. The GQDs/cobaltosilicate composites required lower overpotentials for HER and OER in comparison to the pure GDQs and cobaltosilicate. Moreover, the charge transfer resistance and Warburg impedance was lower than the corresponding values obtained for the pure cobaltosilicate and GQDs. These new GQDs-based composites are expected to open new windows in materials science and electrocatalytic-related processes.

Novel Z-scheme Bi3O4Br/NH2-MIL-125(Ti) composite for efficient photocatalytic degradation of tetracycline

The present work demonstrates the synthesis of the microsphere composite photocatalyst Bi3O4Br/NH2-MIL-125(Ti) (BOB/NMILT) system, and the physicochemical properties of the material were analyzed by various characterization means. Further, the photocatalytic performance of the BOB/NMILT system was evaluated by degrading tetracycline (TC) under simulated sunlight. The degradation rate of TC using BOB/NMILT-5 reached 88.5% within 90 min. The degradation rate is 6.5 times and 3 times higher than that of individual catalysts NH2-MIL-125(Ti) (NMILT) and Bi3O4Br, respectively. The improvement in photocatalytic activity of composites mainly benefited from the construction of heterojunctions, which effectively inhibited the recombination of carriers. Importantly, the role of h+ and •O2− was found to be significant in the reaction of TC. Cumulatively, a Z-scheme photocatalytic degradation mechanism of tetracycline on the BOB/NMILT composite system was proposed. The proposal of this system is of great significance for the future development of photocatalytic materials that can degrade tetracycline.

Ag doped Sn3O4 nanostructure and immobilized on hyperbranched polypyrrole for visible light sensitized photocatalytic, antibacterial agent and microbial detection process.

Ag doped Sn3O4 Nanostructure and immobilized on hyperbranched polypyrrole is investigated in this project. The product was synthesized by the hydrothermal synthesis method. The surface and structural characteristics of the product was studied by different instrumental analysis. The fabricated nanocomposites was utilized as a nano photocatalyst in the removal of methylene blue dye. The crystallography results depicts the triclinic phase of Sn3O4 with the crystallite size 36.3nm. The band gap of the Ag-Sn3O4/hyperbranched polypyrrole was found 1.50eV from kubelka-munk measurements. The specific surface area was increased in the presence of the hyperbranched polypyrrole as compared to Ag-Sn3O4 samples. The photo-catalytic activity of composites was found 100.0% degradation of CR in 30min under visible light irradiation. The catalytic kinetic was followed from the first kinetic model. Moreover, the Ag/Sn3O4/hyperbranched polypyrrole was applied as a bactericidal agent against Streptococcus pneumoniae, and Pseudomonas aeruginosa bacteria. Determination of Streptococcus pyogenes as a pathogenic bacteria was investigated by using aptamer/Ag/Sn3O4/hyperbranched polypyrrole in peroxidase activity. The detection limit of S. pyogenes was 71.0CFU/mL by using the nano-aptamer.

A strategy of silver Ferrite/Bismuth ferrite nano-hybrids synthesis for synergetic white-light photocatalysis, antibacterial systems and peroxidase-like activity

In this paper, the Silver Ferrite/Bismuth ferrite (AgFe2O4/BiFeO3) nanocomposites were fabricated via hydrothermal method. Scanning electron analysis, X-ray diffraction, UV–vis/Kubelka-Munk instrument, specific surface area analysis, and X-ray photoelectron method were utilized to characterize the structural of the prepared nanomaterials. X-ray diffraction shows the cubic and rhombohedral crystal status for composites. The surface area of AgFe2O4/BiFeO3 was 52.41 m2/g. White-light activity of composites was observed due to the bandgap about 1.93 eV. The photocatalytic activity of composites was experimented by using methylene blue dye under visible light irradiation. The dye was completely degraded in 120 min. After fifth cycles, the photocatalysis response was almost constant. The antibacterial study shows that the AgFe2O4/BiFeO3 exposure to Helicobacter pylori and Bacillus cereus with great growth inhibition. The AgFe2O4/BiFeO3 with aptamers was used to detection of Escherichia coli by using the peroxidase activity. The detection limit of Escherichia coli by using Aptamer/AgFe2O4/BiFeO3 as biosensor was about 59 CFU/mL.

Fly Ash Waste Recycling by Pt/TiO2 Incorporation for Industrial Dye Removal.

New materials are obtained by transforming fly ash wastes into a valuable composite, with tandem adsorption and photodegradation properties. Mild hydrothermal synthesis, from titanium dioxide, platinum nanoparticles and zeolite materials obtained from a waste, fly ash, as support, was involved in the composite preparation. The platinum nanoparticles extended the photocatalytic activity of the composite in visible range (Eg = 2.1 eV). The efficiency of tandem adsorption and photocatalytic activity of the new composite were determined to be 25% for Bemacid Blau and 43.89% for Bemacid Rot after 360 min, the irradiation time. The addition of H2O2 improves the process efficiency up to 80.70% and 93.43%, respectively. The Pt nanoparticle (PtNP) contribution led to the band gap energy change to Vis light (400 nm), thus suggesting the possibility of photocatalysis under the action of a fraction of natural light.

Fabrication of Cu2O/Bi2S3 heterojunction photocatalysts with enhanced visible light photocatalytic mechanism and degradation pathways of tetracycline

A novel efficient and visible light-driven p-n heterojunction photocatalyst, cuprous oxide/bismuth sulfide (Cu2O/Bi2S3) was prepared by a simple hydrothermal method. In this study, the photodegradation of tetracycline (TC) by Cu2O/Bi2S3 photocatalyst under visible light was considered. Compared with pure Cu2O and Bi2S3, the photocatalytic Cu2O/Bi2S3 composite has higher catalytic activity for the degradation of TC, and the degradation rate is highest at 95% when the Cu2O content is 10%. The effects of TC concentration and catalyst amount on degradation efficiency were also studied. SEM, XRD and XPS were used to study the morphology, crystal structure and chemical state of the composites and analyze the principle of photocatalytic enhancement. The ultraviolet-visible diffuse reflection (UV–vis DRS) and electrochemical workstation were used to study the photoelectrochemical performance, and the experimental data basis was created for the mechanism analysis. Free radical capture experiments show that superoxide radicals (•O2−) and holes (h+) are the main active species. The improvement in the photocatalytic activity of composites can be attributed to the formation of heterojunctions that expand visible light absorption and effective electron-hole separation. At the same time, we also proposed a possible degradation pathway of tetracycline. This research provides new insights into the development of efficient photocatalysts for treating organic pollutants.

Photocatalytic activity of composites in an AgBr–Ag2CrO4 system prepared by a grinding method with and without washing

Various composites of photocatalysts in the AgBr–Ag2CrO4 system were synthesized via a simple grinding method with and without a washing process. After the starting materials were ground together, the resulting powders showed three phases: AgBr, Ag2CrO4, and KNO3. When these products were washed with deionized water, the KNO3 did not present in the final product. Under visible light irradiation, the prepared photocatalysts can degrade the rhodamine B and reactive orange dyes solutions. Experimental results showed that the KNO3 which was the impurity phase in this system did not affect the photocatalytic activities of prepared photocatalysts. The 0.9AgBr–0.1Ag2CrO4 composite exhibited the best photocatalytic activity and the photocatalytic enhancement of this compound could be attributed to a charge separation. Investigation of inhibitory activity using scavengers confirmed that photogenerated holes and superoxide anion radicals were the primary reactive species produced during the photocatalytic process.

Assembly of MOFs/polymer hydrogel derived Fe3O4-CuO@hollow carbon spheres for photochemical oxidation: Freezing replacement for structural adjustment

We report a new strategy for fabrication of magnetic core–shell Fe3O4-CuO@carbon hollow sphere derived from MOFs/sodium alginate (SA) hydrogel through one-pot synthesis of ferrocene CVD and pyrolysis. Development of freezing-replacement by n-hexane overcame SA capsule shrink induced by heat-treatment and created highly-stable coconut shell-like superstructures, which allowed active sites homogeneously distributed on no-defect surface and improved magnetic and photocatalytic activity of composites. The turn over frequency (TOF) of Fe3O4-CuO@C for organic pollutants degradation was 2.3 h−1 under visible light irradiation, much higher than most of reported catalysts. The synergistic effect of bimetallic clusters and carbon matrix facilitated the charge separation and accelerated H2O2 activation to yield high active radicals. Layer structure and good interfacial contact of metallic sites and porous carbon was beneficial for enhancing photocatalytic activity. The progresses offer a feasible route to rational design of MOF-derived hybrid hollow materials with tailored structure and properties for various applications.

Mpg-C3N4-ZIF-8 composites for the degradation of tetracycline hydrochloride using visible light.

It was found that mesoporous graphite carbon nitride (mpg-C3N4) prepared using melamine as the precursor and ammonium chloride as the bubble template, has good photocatalytic activity under visible light irradiation. In order to improve the photocatalytic performance of mpg-C3N4, it was combined with metal-organic framework ZIF-8. Taking tetracycline hydrochloride (TC) solution as a model pollutant, the photocatalytic activity of composites was studied to select the optimal composite ratio and pH value. The initial concentration of hydrogen peroxide and active oxidation species were also investigated. The results showed that when the loading of ZIF-8 was 40 wt%, the removal efficiency was the best and 74.8% of TC could be removed. The degradation efficiency of TC was negatively affected under extreme pH conditions, but the composite photocatalyst mpg-C3N4-ZIF-8 had a relatively higher degradation efficiency on TC at mild pH values (4-8). The removal efficiency was the best at pH 8, and 75.1% of TC could be removed; the adsorption capacity was 430.7 mg·g-1 and the photodegradation capacity was 548.6 mg·g-1. The order of active species affecting the photocatalytic degradation of TC by mpg-C3N4-ZIF-8 was hole > superoxide radical > hydroxyl radical.

Synthesis, characterization and photocatalytic properties of WO3/hexagonal platelet graphite nanocomposites

The WO3/hexagonal platelet graphite (HPG) composite was successfully prepared by impregnation of ammonium paratungstate (1, 3, 5 and 7 W% W) and hexagonal platelet graphite and subsequent calcination at 500 °C. The synthesized samples were characterized by using powder XRD, FTIR, SEM, DR UV–vis, XPS and N2-physisorption techniques. The characterization results showed that WO3 were well dispersed upon the HPG surface to form nanocomposite structure dependent upon W loading (optimum 5 W%). As compared to bare HPG and WO3, the synthesized W/HPG nanocomposites exhibited significantly enhanced photocatalytic degradation of p-nitrophenol under visible irradiation, providing prevailing evidence for the conjugation of WO3 with HPG. The influence of the reaction time, the catalyst amount, and pH of the solution was studied. The degradation efficiency was reached up to 98% under acidic pH, a catalyst amount of 0.01 g, in a reaction time of 100 min. The evaluation of photocatalytic performance of synthesized nanocomposites for the degradation of p-nitrophenol under visible light irradiation follow the trend: 5W/HPG > 3W/HPG > 7W/HPG > 1W/HPG. After five recycles, the photocatalytic activity of composites did not decline and demonstrated good performance for synthesized composites. The perceived improvement in photocatalytic degradation efficiency of the WO3-HPG nanocomposites could be attributed to the synergy of the well narrowed band gap, high surface area and effectual control of e−-h+ recombination.

Enhanced photocatalytic degradation of industrial dye by g-C3N4/TiO2 nanocomposite: Role of shape of TiO2

The photocatalytic degradation of toxic dyes has brought a new revolution to reduce water pollution. To degrade industrial dyes, TiO2 is an important photocatalyst but the role of morphology is also important in degradation. We have synthesized g-C3N4/TiO2 nanocomposite (1:1) having different shapes of TiO2 (nanorods (NR), nanospheres (NS), and nanotubes (NT)), to show the effect of morphology on its photocatalytic activity. To improve the photocatalytic efficiency of TiO2 in visible light, we have incorporated g-C3N4, a visible light active photocatalyst. The HRTEM, FESEM and Electron Diffraction studies with color mapping indicate successful synthesis of g-C3N4/TiO2 nanocomposites. The increased photocatalytic efficiency of the nanocomposites regarding the degradation of Rhodamine B (RhB) dye under visible light irradiation is due to the incorporation of g-C3N4 with different shapes of TiO2. The studies show that, the shape of TiO2 has a remarkable effect in photodegradation. The best degradation performance (∼97%) was obtained from g-C3N4/TiO2 -nanotubes composite with a rate constant of 0.0403 min−1 within 80 min, whereas degradation efficiency of other shapes of TiO2 like NS (92%) and NR (94.5%) were also found to be greater than that of commercial TiO2 (P25) composite (74%). Results from UV–Vis absorption study, X-ray Diffraction studies, X-ray photoelectron spectroscopy and BET analysis suggest that the improvement in photocatalytic activity of composite is due to increased light absorption in visible region and increase in surface area (137.1 m2/g). Results from different scavengers study (DMSO, ascorbic acid and methanol) indicate that electron and superoxide ions act as main reactive species in photodegradation of RhB dye. The reusability efficiency of the catalyst shows 86% degradation after 5 consecutive cycles. The effect of pH and catalyst concentration was also determined which shows that maximum degradation occurs at pH ∼ 7 (98%) and degradation efficiency is increased with increase of catalyst dose from 0.1 mg/ml to 0.6 mg/ml and after that saturation occur due to increase in opacity and scattering of light. A comparative study was done with literature which suggests that this nanocomposites act as one of the best photocatalysts for degradation of toxic dyes.

Simultaneous and efficient photocatalytic reduction of Cr(VI) and oxidation of trace sulfamethoxazole under LED light by rGO@Cu2O/BiVO4p-n heterojunction composite

Antibiotics and heavy metals often coexist in polluted environment, and the harm of combined pollution is greater than that of single pollution. In this study, a series of graphene supported p-n heterojunction rGO@Cu2O/BiVO4 composites are synthesized with different Cu2O doping for simultaneous detoxification of Cr(VI) and antibiotics. The obtained photocatalysts (rGO@Cu2O/BiVO4) with proper loading amount of Cu2O shows the a high photocatalytic degradation activity for simultaneously efficient Cr(VI) reduction and sulfamethoxazole (SMZ) oxidation under LED light at neutral pH. The Cr(VI) was completely transformed to Cr(III) rather than simply Cr(VI) adsorbed on the surface of rGO@Cu2O/BiVO4. The photocatalytic activity of composites can be attributed to excellent electrical conductivity of rGO and the p-n heterojunction between Cu2O and BiVO4, which promotes the spatial separation of photogenerated charges at the heterojunction boundary and inhibits of the photogenerated h+ and e− recombination. It's confirmed that h+, O2− and OH are the main reactive species for the photocatalytic SMZ oxidation, and the most important reactive species is h+. Finally, the tentative degradation pathways of SMZ are proposed based on the liquid chromatography-triple quadrupole mass spectrometry analysis. This work provides an effective approach for the treatment of water that contains SMZ and Cr(VI) under LED light.

Coloading of TiO2 and C3N4 on kaolinite nanotubes for obviously improved photocatalytic performance in degradation of methylene blue dye

kaolinite nanotubes (KNTs) were firstly used to coload TiO2 nanoparticles and carbon nitride (C3N4) nanosheets for photocatalytic degradation of methylene blue (MB) dye. The influence of C3N4 amount on the photocatalytic activity of composites was evaluated. The optimum sample showed an ultrahigh efficiency/effective mass ratio that is 18.8 and 24.7 times higher than these of pure TiO2 and C3N4 references, respectively. The enhancement of photocatalytic performance for clay-semiconductor composites can be attributed to the Z-scheme transport of photoproduced electrons and the good dispersion of catalyst particles on KNTs. The work provides an example that KNTs can be used as a promising support with very little catalysts but high photocatalytic performance.

The Construction of the Heterostructural Bi2O3/g-C3N4 Composites with an Enhanced Photocatalytic Activity

A heterostructural composite composed of g-C3N4 and Bi2O3 was achieved by the one-pot and thermal-induced polycondensation method using melamine and Bi(NO[Formula: see text] as precursor at 550[Formula: see text]C under air atmosphere. The crystalline phase, components and morphologies of the as-prepared composites were investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). Besides, the photocatalytic activity of composites was evaluated by degrading RhB aqueous solution at room temperature under visible light irradiation. Compared with bulk g-C3N4, the photocatalytic efficiency of the 0.5% Bi2O3/g-C3N4 (Bi–CN) was increased by up to four times. The introduction of Bi2O3 enhances not only the light absorption ability, but also the separation of photogenerated electron–hole pairs.

Sb2WO6 nanoparticles coated TiO2 nanobelts exhibiting remarkable photo-catalyst response

Sb2WO6/TiO2 composites with different contents of Sb2WO6 were successfully synthesized through a facile hydrothermal method. The Sb2WO6/TiO2 composites were characterized by X-ray diffraction (XRD), UV-visible diffuse reflectance spectra (UV–vis DRS), photoluminescence spectra (PL), scanning electron microscope (SEM) and transmission electron microscope (TEM). Sb2WO6 nanoparticles are distributed uniformly on the surface of TiO2 nanobelts in the prepared Sb2WO6/TiO2 composites. The effect of Sb2WO6 content on the photocatalytic activity of composites is studied by UV–vis DRS and PL. All Sb2WO6/TiO2 photocatalysts show enhanced photocatalytic activity and excellent recycling property for degrading rhodamine B (RhB) under visible light irradiation. The 30% Sb2WO6/TiO2 sample shows the best photocatalytic activity. Its kinetic constant (0·476/h) is 21·6 times higher than that of TiO2. The possible photocatalytic mechanism is discussed according to the trapping experiments of active species. The improved photocatalytic activity for the Sb2WO6/TiO2 catalyst may be attributed to the synergetic effect between Sb2WO6 nanoparticles and TiO2 nanobelts. The enhanced photocatalytic activity and excellent stability make this material a promising candidate for degrading environmental pollutants in the future.

Reduced graphene oxide and titania nanosheet cowrapped coal fly ash microspheres alternately as a novel photocatalyst for water treatment

A novel photocatalyst with core@shell structure was prepared by alternately assembling titania nanosheets (TNS) and reduced graphene oxide (r-GO) on coal fly ash (CFA) microspheres via the layer-by-layer (LBL) assembly approach. The as-prepared samples CFA@(r-GO/TNS)n were characterized by SEM, HRTEM, XRD, FTIR, Raman, XPS, UV–vis, PL and their photocatalytic activities were evaluated by the photodegradation of methylene blue (MB) under UV irradiation. The results showed that TNS and r-GO wrapped on the surface of CFA alternately and tightly, which was very helpful not only to avoid the detachment of TNS and r-GO from the surface of CFA in the progress of using, but also to reduce the recombination of photogenerated electrons and holes due to excellent mobility of charge carriers on the surface of r-GO. The layer number of wrapped r-GO/TNS was found to be an important factor in the photocatalytic activity of composite. In our experimental conditions, CFA@(r-GO/TNS)8 presented the best photocatalytic activity, and the degradation efficiency of MB was improved to 55% from 32% of CFA@(r-GO/TNS)2. The improvement could be attributed to several advantageous factors by introduction of r-GO, such as the fast charge-carrier transfer, the reduction of the charge recombination rate, the improved light harvesting and the larger specific surface area.

Novel Visible-Light-Driven Photocatalyst Co3O4/FeWO4 for Efficient Decomposition of Organic Pollutants

A highly efficient and visible light (λ ≥ 420 nm) responsive composite photocatalyst, Co3O4/FeWO4 was prepared by simple impregnation method. The heterojunction semiconductors Co3O4/FeWO4 demonstrated notably high photocatalytic activity over a wide range of composition than the individual component Co3O4 or FeWO4 for the complete degradation of 1,4-dichlorobenzene (DCB) in aqueous phase under visible light irradiation. The photocatalytic activity of composite was optimized at 1/99 Co3O4/FeWO4 composition. After 2 h of visible light irradiation 51% decomposition of 1,4-dichlorobenzene (DCB) was observed utilizing 1/99 Co3O4/FeWO4 photocatalyst while the end members demonstrated a negligible degradation under the same experimental condition. The valence band (VB) and conduction band (CB) of Co3O4 is located above the VB and CB of FeWO4, respectively. Both the semiconductors Co3O4 and FeWO4 exhibit strong absorption over the wide range of visible light. The obviously enhanced photocatalytic performance of Co3O4/FeWO4 composite has been discussed on the hole (h+) as well as electron (e−) transfer mechanism between the VB and CB of individual semiconductors.

Preparation, Characterization and Application of Polyaniline/silk Fibroin Composite

We report the electrical properties and photocatalytic activity of polyaniline (Pani) and polyaniline/silk fibroin (Pani/SF) composite. The Pani/SF composite has been synthesized first time by chemical oxidative in-situ polymerization method by using potassium persulphate (K2S2O8) in an acidic medium. Thus prepared Pani and Pani/SF composite were characterized by using Fourier-transform infrared spectroscopy, x-ray diffraction, thermogravimetric analysis and scanning electron microscopy. The stability in terms of the DC electrical conductivity of Pani/SF composite and Pani was investigated under isothermal and cyclic aging conditions. Results indicated that the electrical properties of the composite were significantly influenced by the loading of SF to Pani and observed to be more thermally stable than those of Pani. As-prepared Pani and Pani/SF composites were studied for the degradation of methylene blue (MB) and Rhodamine B (RhB) under UV-light irradiations. The results showed that 91.4% & 85.4% degradation of RhB and MB takes place respectively after 90 min over Pani/SF composite. The decomposition rate of composite was 1.8-2.2 times greater than that of Pani. The improvement of photocatalytic activity of composite may be attributed to the electron-sink function of silk fibroin which increases the optical absorption property and separation of photogenerated charge carriers than Pani alone.