Enhanced photocatalytic performance of Cu2O nano-photocatalyst powder modified by ball milling and ZnO

Cellulose supported TiO2/Cu2O for highly asymmetric conjugate addition of α,β-unsaturated compounds in aqueous phase

A series of new kind green cellulose-supported bimetallic TiO2/Cu2O (Cell@TiO2/Cu2O) catalytic materials were obtained by in-situ reduction method employing cellulose as the carrier. The effects of metal percentage composition on the morphology and construction of the catalytic materials were systematically investigated. The Cell@TiO2/Cu2O were characterized by FT-IR, TG, XPS, SEM, TEM, EDS, and the element content was obtained by elemental analysis. Then, the achieved catalytic materials were applied to the chiral borylation reaction of α,β-unsaturated compounds, including nitrile compounds, esters, and α,β-unsaturated ketones. Remarkably, this approach provides an efficient strategy to gain an important class of chiral organic boron compounds with target chiral products in high yields as well as enantioselectivities. Besides, the Cell@TiO2/Cu2O could be easily recycled and effectively reused. This work constructed bimetallic TiO2/Cu2O on cellulose as a newly catalyst to obtain chiral boron compounds in aqueous phase.

Biogenic fabrication and enhanced photocatalytic degradation of tetracycline by bio structured ZnO nanoparticles

ABSTRACTZinc oxide nanoparticles (ZnO NPs) were synthesized using Zinc Nitrate as precursor salt, and plant leaves extracts from Azadirachta indica (Common name: Neem), Cymbopogan citratus (Common name: Lemongrass), and Mangifera indica (Common name: Mango), as both chelating and reducing agents for the synthesis of ZnO NPs by a simple cost-effective and eco-friendly green method. The biosynthesized ZnO NPs were well characterized by various methods. XRD pattern revealed a hexagonal wurtzite phase of ZnO, with no other impurity peaks present revealing XRD crystalline sizes of 13.94-16.37 nm calculated using Scherrer equation. The XPS confirmed the presence of Zn, O, and C, and the carbon peaks are almost in agreement with peaks observed by FT-IR. TEM showed the different ZnO with spherical shapes and some aggregations. BET surface area gave 24.98, 21.62, and 22.72 m²/g, respectively for ZnO-AI, ZnO-Cyc, and ZnO-MI, while BJH pore volume and average pore diameter were estimated to be 0.217 cc/g, 0.209 cc/g, 0.211 cc/g, and 2.132 nm, 2.025 nm, and 2.100 nm respectively for ZnO-AI, ZnO-Cyc, and ZnO-MI.Furthermore, the bio-synthesized ZnO NPs were evaluated for their catalytic and photocatalytic performance in the degradation of aqueous tetracycline (TC). The biosynthesized ZnO NPs exhibit good photodegradation efficiency for TC in varying degrees with ZnO-AI > ZnO-MI > ZnO-Cyc. Optimum operational parameters for TC degradation using the ZnO-AI were established, and maximum degradation efficiency of 84.8% was obtained. In addition, the catalyst can also be regenerated and reused up to three cycles, with the third cycle still achieving greater than 80% TC degradation.

Impact of Ball Milling on the Hydrogen Evolution Performance of Cu2Sn0.38Ge0.62S3 Photocatalytic Particles Synthesized via a Flux Method

Ball milling has been shown empirically to produce fine photocatalytic particles from large bulky particles but to drastically reduce the photocatalytic activity of such material during water splitting due to mechanical damage to the photocatalyst surfaces. If the damaged photocatalyst surfaces could be removed or reconstructed, the reduced particle sizes resulting from milling would be expected to provide enhanced photocatalytic activity. In the present study, fine particles of crystalline Cu₂Sn_0.38Ge_0.62S₃ (CTGS), which is responsive to long wavelength light up to the near-infrared region, were synthesized by a flux method and subsequent ball milling. A photocathode made of such particles showed significantly enhanced photoelectrochemical (PEC) performance under simulated sunlight while the photocatalytic hydrogen evolution activity of a powder suspension system made from the same material exhibited a typical decrease. The CTGS crystalline particles synthesized using the flux method were found to be highly crystalline but to have relatively large micrometer-scale sizes. Ball milling reduced the particle size but produced an amorphous coating of oxidized species that lowered the photocatalytic activity of the powder suspension system. Typical surface modifications of a photocathode made from this material, consisting of wet chemical processes, also served as an etching treatment to successfully remove the minimally crystalline surface layer and provide greater PEC activity. These data suggest the benefits of combining flux crystal growth with ball milling and the appropriate chemical etching process to obtain high-crystallinity fine photocatalytic particles responsive to long wavelength light with improved PEC hydrogen evolution activity.

Renewable and eco-friendly ZnO immobilized onto dead sea sponge floating materials with dual practical aspects for enhanced photocatalysis and disinfection applications

In this study, we have investigated the role of natural dead sea sponge (DSS, Porifera) as a three-dimensional (3D) porous host substrate for the immobilization of nanostructured ZnO material towards the development of ZnO based floating photocatalysts for efficient removal of methylene blue (MB) dye under the illumination of sunlight. After photodegradation, the treated water after dye degradation contains several pathogens, different disinfectants or chemical reagents that are essentially used. This is not the case for DSS as it can naturally kill any pathogens during the wastewater treatment process. To explore these functions, ZnO nanosheets were incorporated onto DSS via hydrothermal protocol and the as prepared ZnO/DSS hybrid material exhibited approximately ∼100% degradation efficiency for the removal of MB. Importantly, the degradation kinetics associated with the fabricated ZnO/DSS was remarkably accelerated as evidenced by the high values of degradation reaction rate constants (3.35 × 10^-2min^-1). The outperformance of ZnO/DSS could be attributed to the adsorption caused by its 3D porous structure together with the high rapid oxidation of MB. Furthermore, the high charge separation of electron-hole pairs, natural porosity, and abundant catalytic sites offered by the hybrid ZnO/DSS floating photocatalyst have enabled quantitative (∼100%) degradation efficiency for MB. Finally, the excellent reusability results confirm the feasibility of using natural ZnO/DSS-based photocatalyst for practical solution of wastewater treatment and other environmental problems.

Control over the Surface Properties of Zinc Oxide Powders via Combining Mechanical, Electron Beam, and Thermal Processing

The surface properties of zinc oxide powders prepared using mechanical activation, electron beam irradiation, and vacuum annealing, as well using combinations of these types of treatments, were studied using X-ray photoelectron spectroscopy. The structure of the obtained materials was studied by an X-ray diffraction technique and by scanning electron microscopy. We found that over five hours of grinding in an attritor, the size of nanocrystals decreases from 37 to 21 nm, and microdeformations increase from 0.3% to 0.6%. It was also found that a five-hour grinding treatment promoted formation of vacancies in the zinc sublattice at the surface and diffusion of Zn2+ cations into the bulk of the material. Irradiation of commercial zinc oxide powders with an electron beam with an energy of 0.9 MeV and a dose of 1 MGy induced breaking of Zn–O bonds, diffusion of interstitial zinc ions into the bulk, and oxygen atom escape from regular positions into the gas phase. A combined treatment of five hours of grinding and electron beam irradiation promoted accumulation of interstitial zinc ions at the surface of the material. Annealing of both initial and mechanically activated ZnO powders at temperatures up to 400 °C did not lead to a significant change in the properties of the samples. Upon exceeding the 400 °C annealing temperature the X-ray photoelectron spectra show almost identical atomic composition of the two types of materials, which is related to diffusion of interstitial zinc ions from the bulk of the material to the surface.

Adsorption and photocatalytic properties of porphyrin loaded MIL-101 (Cr) in methylene blue degradation

In this study for the very first time, zinc tetraphenylporphyrin (ZnTPP) was loaded into MIL-101 (Zn[TPP]@MIL-101) to perform an adsorptive and photocatalytic dye removal. The physicochemical attributes of the catalyst were thoroughly determined by the usage of XRD, FTIR, FESEM, BET, UV-vis, and inductively coupled plasma (ICP). The obtained XRD pattern exhibited the phase purity of MIL-101 and its structural stability. The solid-phase diameter of the catalyst was observed to be ~ 270.76 ± 119.95 nm, while its gas adsorption data was indicative of a decrease in the specific surface area after the loading of ZnTPP. The ICP analysis displayed the amount of encapsulated Zn[TPP] (~ 17%) in MIL-101. The UV-vis confirmed the presence of Zn[TPP] in MIL-101 with the lack of any interferences or overlaps with the λ_max of methylene blue (MB) with the support. The dye removal of MB was investigated under dark conditions (adsorption) and UV light (photodegradation). The observed adsorption under dark conditions using Zn[TPP]@MIL-101 (99.27% yield) demonstrated a superior dye removal in comparison to the cases of photodegradation of MB by MIL-101 and Zn[TPP]@MIL-101 or adsorption by MIL-101. In conformity to the gathered results, [ZnTPP] was able to increase the adsorption capacity at pH = 7 at room temperature.

Enhanced photocatalytic performance of ZnO/AgCl composites prepared by high-energy mechanical ball milling

ZnO/AgCl composites prepared by high-energy ball milling showed excellent photocatalytic activity for RhB degradation and 1,4-DHP dehydrogenation under visible-light irradiation.

La2Sn2O7/g-C3N4 nanocomposites: Rapid and green sonochemical fabrication and photo-degradation performance for removal of dye contaminations

The deficiency of drinking water sources has become a serious crisis for the future of the world that the photocatalytic process is one of the most favorable methods for removal of artificial dyes and poisonous organic impurities. In the present study, rapid ultrasonic treatment was performed to obtain La₂Sn₂O₇/Graphitic carbon nitrides (LSO/CN) nanocomposites with advanced photo-catalytic performance. Broccoli extract was utilized as a natural surfactant with active surface groups to control nucleation and growth of formed crystals with the creation of spatial barriers around the cations, and finally prevent nano-product agglomeration. Changing experimental parameters in synthesis reaction in turn offers a virtuous control over the nano-products size and shape. The shape and size distribution of particles was considered via diverse characterization techniques of microscopic and spectroscopic. The photocatalytic behaviors along with a kinetic study of the nanoparticles were examined by elimination and degradation of different artificial dyes under the UV waves. Effect of particle size, weight ratio of LSO:CN, type of dye, scavenger kind, dye and catalyst loading was designated on altering proficiency of nano-catalyst function. Also, the probable mechanism of removal dye by photocatalytic function was studied.

Recent advances in Cu2O-based composites for photocatalysis: a review

Cu₂O-based composites for photocatalysis have been extensively explored owing to their promising application in solving environmental and energy problems. At present, the research on photocatalysis is focused on improving the photocatalytic performance of materials. It has been reported that adjusting the morphology and size of Cu₂O can effectively improve its photocatalytic property. However, photocorrosion is still an inevitable problem, which hinders the application of Cu₂O in photocatalysis. The strategies of constructing heterogeneous nanostructures and ion doping can significantly improve the light stability, light absorption capacity and separation efficiency of electron-hole pairs. Cu₂O-based composites exhibit superior performances in degrading organic matter, producing hydrogen, reducing CO₂ and sterilization. Therefore, the construction of multi-materials will be one of the future directions in their photocatalytic application. This review summarizes the recent strategies for enhancing the photocatalytic activity of Cu₂O by analyzing different Cu₂O-based photocatalysts, and the charge transfer pathway is further discussed in detail. Finally, several opportunities and challenges in the field of photocatalysis are illustrated.

Preparation and Characterization of Zinc Oxide Nanoparticles Using Leaf Extract of Sambucus ebulus

Plants are one of the best sources to obtain a variety of natural surfactants in the field of green synthesizing material. Sambucus ebulus, which has unique natural properties, has been considered a promising material in traditional Asian medicine. In this context, zinc oxide nanoparticles (ZnO NPs) were prepared using S. ebulus leaf extract, and their physicochemical properties were investigated. X-ray diffraction (XRD) results revealed that the prepared ZnO NPs are highly crystalline, having a wurtzite crystal structure. The average crystallite size of prepared NPs was around 17 nm. Green synthesized NPs showed excellent absorption in the UV region as well as strong yellow-orange emission at room temperature. Prepared nanoparticles exhibited good antibacterial activity against various organisms and a passable photocatalytic degradation of methylene blue dye pollutants. The obtained results demonstrated that the biosynthesized ZnO NPs reveal interesting characteristics for various potential applications in the future.