Photocatalytic Activity Of Composite Materials Research Articles

Enhancing the photocatalytic and antimicrobial activity of ZnFe2O4 by composite with Ag2WO4 semiconducting material

In this research article, we have performed the degradation of methylene blue dye (MB) in the presence of ZnFe2O4/Ag2WO4 photocatalyst. These catalyst materials are prepared by a simple combustion method followed by a solution mixing method. The structure and morphology of prepared composite material are analyzed by using XRD, FTIR, UV-DRS, and scanning electron microscopy. The antimicrobial property of composite material is studied against E. coli and S. aureus food pathogenic bacteria. After the incubation time, the antimicrobial activity of the composite material shows a clear zone of inhibition This composite photocatalyst is a promising material to increase the degradation percentage of MB (Methylene blue) dye in the presence of UV light. ZnFe2O4/Ag2WO4 composite material shows 72.72% degradation of the MB dye. The photocatalytic activity of composite material has been performed by varying the catalyst dosage and pH level of the medium used for the degradation process. The role of composite material in the degradation of dye and their increase in the reaction rate has also been discussed. From these results, the ZnFe2O4/Ag2WO4 composite is a good material to degrade the toxic pollutants in the environment.

Insight into Fe-O-Bi electron migration channel in MIL-53(Fe)/Bi4O5I2 Z-scheme heterojunction for efficient photocatalytic decontamination

Building a heterojunction is a fascinating option to guarantee sufficient carrier separation and transfer efficiency, but the mechanism of charge migration at the heterojunction interface has not been thoroughly studied. Herein, MIL-53(Fe)/Bi4O5I2 photocatalyst with a Z-scheme heterojunction structure is constructed, which achieves efficient photocatalytic decontamination under solar light. Driven by the newly-built internal electric field (IEF), the formation of Fe-O-Bi electron migration channel allows for rapid separation and transfer of charge carriers at the heterojunction interface, confirmed by the material characterization and density functional theory (DFT) calculation. The narrower band gap and improved visible light response also contribute to the enhanced photocatalytic activity of composite materials. With levofloxacin as the target pollutant, the optimal MIL-53(Fe)/Bi4O5I2 achieves complete removal of pollutant within 150 min, the photocatalysis rate of which is ca. 4.4 and 26.0 times that of pure Bi4O5I2 and MIL-53(Fe), respectively. Simultaneously, the optimal composite material exhibits satisfactory photodegradation of seven fluoroquinolones, and the photocatalysis rates are as follows: lomefloxacin > ciprofloxacin > enrofloxacin > norfloxacin > pefloxacin > levofloxacin > marbofloxacin. DFT calculations reveal a positive relationship between degradation rate and Fukui index (ƒ0) of main carbon atoms in seven fluoroquinolones. This study sheds light on the existence of electron migration channels at Z-scheme heterojunction interface to ensure sufficient photoinduced carrier transfer, and reveals the influence of pollutant structure on photolysis rate.

Flower-like spherical ZnCdS/Bi2WO6/ZnAl-LDH with dual type II heterostructure as a photocatalyst for efficient photocatalytic degradation and hydrogen production

One of the effective strategies for improving the photocatalytic activity of composite materials is to construct a heterostructure using layered double hydroxide (LDH) as the main photocatalytic material in order to accelerate photogenerated charge transfer. We report herein the preparation of a novel flower-like spherical photocatalytic composite, ZnCdS/Bi2WO6/ZnAl-LDH, with a dual type II heterostructure, by a hydrothermal method. ZnAl-LDH in the composite has the characteristic structure of a good hydrotalcite-like compound, and ZnCdS and Bi2WO6 are loaded on its surface to form flower-like spherical particles of uniform size. Compared with ZnAl-LDH, a ZnCdS/Bi2WO6/ZnAl-LDH composite has a significantly broader light absorption range and a more uniform pore size distribution. Electrochemical impedance, transient photocurrent, and photoluminescence results for ZnCdS/Bi2WO6/ZnAl-LDH composites have shown that the composition with 20% ZnCdS displayed the highest photocurrent density, the lowest electron-transfer resistance, and the lowest electron–hole recombination efficiency. Multi-mode photocatalytic degradation experiments showed all ZnCdS/Bi2WO6/ZnAl-LDH composites to exhibit good photocatalytic degradation ability. Meanwhile, ZnCdS/Bi2WO6/ZnAl-LDH showed enhanced hydrogen production of 79.20 μmol g−1 h−1, more than eight times that for ZnAl-LDH, and its photocatalytic activity remained stable after three experimental cycles. Through trapping experiments, the active species involved in the photocatalytic reaction has been identified, and the presence of a dual type II heterostructure in the ZnCdS/Bi2WO6/ZnAl-LDH composite is postulated. Rapid separation and migration of photogenerated charge carriers in the composite is achieved due to the close association of ZnCdS, Bi2WO6, and ZnAl-LDH.

Efficient Visible-Light-Induced Photocatalytic Removal of Salicylic Acid Using Sulfur-Doped Fe<sub>3</sub>O<sub>4</sub>/SiO<sub>2</sub>/TiO<sub>2 </sub>Composite

This research has prepared Fe3O4/SiO2/TiO2-S composite materials as magnetic photocatalysts. Detailed characterization of the composite materials was undertaken using FTIR, XRD, TEM, VSM and DRUV. The photocatalytic activity of composite materials was conducted through salicylic acid degradation under visible light illumination. The result based on the infrared spectra and XRD diffractogram revealed the appearance of the characteristic peak of Fe3O4, SiO2, and S-TiO2. The sulfur doping causes an absorption edge shifts toward a higher wavelength. Fe3O4/SiO2/TiO2-S 3% composite material had the narrowest band gap energy of 2.77 eV and presented good photocatalytic activity with a percentage degradation of 91.6% under visible light during 60 minutes of illumination time. The composite exhibited recoverable efficiency due to its magnetic properties.

Novel Zn-Al LDHs based S-scheme heterojunction with coral reef-like structure for photocatalytic activation of peroxymonosulfate towards nitenpyram decomposition

The construction of an S-scheme heterojunction is an effective way to enhance the photocatalytic activity of composite materials. Thus, a co-precipitation method is combined with a hydrothermal synthesis method in this study to synthesize an S-scheme heterojunction of Bi2WO6/Ag3PO4/Zn-Al LDH photocatalyst with an exceptional morphology like a coral reef. On this basis, an AP0.5BWLDH0.3/PMS/Vis reaction system is constructed. The prepared Bi2WO6/Ag3PO4/Zn-Al LDH composites present better oxidation performance than pure Bi2WO6, Zn-Al LDH and Ag3PO4, with 100% Nitenpyram (50 mg/L) degraded within 90 min due to the photocatalytic activation of peroxymonosulfate. The significant increase in photocatalytic activity is not only due to the uniformly distributed coral reef-shaped nanostructures but also the extended life of the carrier with strong redox capability through S-scheme heterojunction. During the simulated exposure to sunlight, the internal electric field, optimized energy band structure, as well as coulomb force interaction all contributed to the promotion of the transportation of electron-hole pairs in the Bi2WO6/Ag3PO4/Zn-Al LDH composite. For this reason, electrons and holes have high reducing and oxidizing properties, which make the composites have high redox capacity. Then the radical trapping experiments, ESR testing and XPS analysis were used to verify these results. It was revealed that the S-scheme heterojunction mechanism was suitable for the electron migration in a photocatalyst. This study extends the design and preparation ideas of new S-scheme heterojunction photocatalysts and then proposes effective strategies to solve future water pollution.

Stable Ti3+ in B-TiO2/BN based hybrids for efficient photocatalytic reduction

Herein, we explored a new 2D heterostructure by hybridizing BN and TiB2, especially the photocatalytic activity of composite materials. Based on the key strategy of developing BN hybrid photocatalysts to change the band structure, we studied the influences of TiB2 addition on the structures and photocatalytic performances of Ti3+-B codoped TiO2/BN. The Ti3+ existed in TiBO3 enables excellent photocatalytic performances in hydrogen production and nitrogen fixation compared with pure BN. We also carried out first-principle calculations using the VASP program to explain the excellent photocatalytic hydrogen production performances. Finally, the photocatalytic mechanism of such TiO2/BN hybrid photocatalysts was proposed.

Preparation of ZnO-GO nanocomposites and their properties

ZnO nanoparticles were prepared by hydrothermal method. The modified Hummer process was then used to prepare go. The ZnO-GO com posites were then mixed to produce different ratios of ZnO-GO, characteris ed and their photocatalytic properties were investigated using rhodamine B as the target degradation species. The results showed that the degradation r ates of rhodamine B were 41.96% and 84.42% for the nano-ZnO and ZnO-GO 7% composites, respectively, when illuminated with xenon light for 36 0 min. The improved photocatalytic activity of composite materials is prim arily due to the introduction of appropriate amount of GO, which could ra pidly capture and transfer to the photogenerated electrons, and could load more ZnO and prevent the agglomeration of ZnO particles, increasing the s pecific surface area of ZnO and its activation point, as well as increasing th e adsorption of pollutants on the ZnO surface and improving the photocatal ytic efficiency.

Sulfur-doped g-C3N4/TiO2 S-scheme heterojunction photocatalyst for Congo Red photodegradation

Constructing step-scheme (S-scheme) heterojunctions has been confirmed as a promising strategy for enhancing the photocatalytic activity of composite materials. In this work, a series of sulfur-doped g-C3N4 (SCN)/TiO2 S-scheme photocatalysts were synthesized using electrospinning and calcination methods. The as-prepared SCN/TiO2 composites showed superior photocatalytic performance than pure TiO2 and SCN in the photocatalytic degradation of Congo Red (CR) aqueous solution. The significant enhancement in photocatalytic activity benefited not only from the 1D well-distributed nanostructure, but also from the S-scheme heterojunction. Furthermore, the XPS analyses and DFT calculations demonstrated that electrons were transferred from SCN to TiO2 across the interface of the SCN/TiO2 composites. The built-in electric field, band edge bending, and Coulomb interaction synergistically facilitated the recombination of relatively useless electrons and holes in hybrid when the interface was irradiated by simulated solar light. Therefore, the remaining electrons and holes with higher reducibility and oxidizability endowed the composite with supreme redox ability. These results were adequately verified by radical trapping experiments, ESR tests, and in situ XPS analyses, suggesting that the electron immigration in the photocatalyst followed the S-scheme heterojunction mechanism. This work can enrich our knowledge of the design and fabrication of novel S-scheme heterojunction photocatalysts and provide a promising strategy for solving environmental pollution in the future.

Efficient photo-catalytic hydrogen production performance and stability of a three-dimensional porous CdS NPs-graphene hydrogel

We designed a novel CdS nanoparticles composite graphene hydrogel. Under sunlight, the CdS nanoparticles (NPs) -reduced graphene oxide hydrogel (rGH) had the highest hydrogen production rate of 6.44 mmol/g, which is 1.3 times that of CdS nanoparticles (5.12 mmol/g) and 1.4 times that of CdS (4.6 mmol/g). The enhanced photo-catalytic activity can be attributed to several positive factors such as the formation of composite hydrogels and the quantum size effect of the CdS nanoparticles nanomaterials. The formation of the composite hydrogel improves the specific surface area of the catalyst and increases the active site on the catalyst surface. The quantum size effects of the CdS nanoparticles effectively reduce the recombination probability of electrons and holes. The close contact between the CdS nanoparticles and the graphene gel can effectively separate photo-generated electrons and holes via the unique large π-bond structure of graphene. These positive factors effectively improve the photocatalytic activity of composite materials for water decomposition. In addition, recovery experiments show a composite catalyst recovery rate of up to 95%. The results show that the composite photo-catalyst can effectively avoid secondary pollution during photo-catalytic hydrogen production. This eliminates powder recovery problems. The hydrogen production efficiency of the catalyst remains unchanged after 5 cycles indicating that the formation of the gel system stabilizes the catalyst and inhibits light corrosion of CdS nanoparticles.

Preparation and properties of hydroxyapatite/titania composite for microbial filtration application

A series of TiO2 modified hydroxyapatite composites (HA/TiO2) with different compositions were prepared. Phase formations and morphologies of the obtained HA/TiO2 composite were characterised using X-ray diffraction and SEM, and their photocatalytic activities were also determined by decomposition of methylene blue solution. Filter cloths were prepared by depositing the composite on polyester non-wovens via pad dry cure, and their filtering effectiveness was examined by photocatalytic activity measurement and bactericidal test. Hydroxyapatite/TiO2 composites were successfully prepared and exhibited photocatalytic properties. With increasing ratio of anatase titania in the HA/TiO2 composite from 20 to 30 and 50%, photocatalytic activity of composite material increased such that HATi5050 composite exhibited the highest photocatalytic activity. Non-woven filters coated with HA/TiO2 composites also exhibited good photocatalytic activities. Less difference in photocatalytic activity between HATi7030 and HATi5050 coated non-woven filters was observed, compared to that in powder form. The filter coated with HA/TiO2 composite exhibited good bactericidal effect.

N, S co-doped-TiO2/fly ash beads composite material and visible light photocatalytic activity

Using TiCl4 as the titanium source, urea as the precipitating agent, nano-TiO2/fly ash beads composite materials were prepared by hydrolysis-precipitation method. Using (NH2)2CO and (NH2)2SC as the N and S source respectively, N and S co-doped TiO2/fly ash beads composite materials were prepared by grinding them together according to a certain proportion and calcined at 500°C for 2h. The composite materials were characterized by SEM, EDS, XPS, and UV–vis spectrophotometer methods. The UV–vis absorption spectra results show that the absorption edge of un-doped composites is 390nm while that of doped composites red-shifts to 500nm. The photocatalytic activity of composite materials was evaluated by degradation of methyl orange under visible light irradiation (halogen lamp, 250W). The results showed that after irradiation for 1h, degradation rate of N, S co-doped-TiO2/fly ash beads composite material can reach 65%, while the degradation rate of un-doped sample and P25 were just 10% and 6%, respectively. The composite material also showed excellent recycling properties.