Photocatalytic Activities Of As-synthesized Samples Research Articles

Synthesis, Characterization, Photocatalysis, and Antibacterial Study of WO3, MXene and WO3/MXene Nanocomposite.

Tungsten oxide (WO3), MXene, and an WO3/MXene nanocomposite were synthesized to study their photocatalytic and biological applications. Tungsten oxide was synthesized by an easy and cost-effective hydrothermal method, and its composite with MXene was prepared through the sonication method. The synthesized tungsten oxide, MXene, and its composite were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR), energy-dispersive X-ray analysis (EDX), and Brunauer–Emmett–Teller (BET) for their structural, morphological, spectral, elemental and surface area analysis, respectively. The crystallite size of WO3 calculated from XRD was ~10 nm, the particle size of WO3 was 130 nm, and the average thickness of MXene layers was 175 nm, which was calculated from FESEM. The photocatalytic activity of as-synthesized samples was carried out for the degradation of methylene blue under solar radiation, MXene, the WO3/MXene composite, and WO3 exhibited 54%, 89%, and 99% photocatalytic degradation, respectively. WO3 showed maximal degradation ability; by adding WO3 to MXene, the degradation ability of MXene was enhanced. Studies on antibacterial activity demonstrated that these samples are good antibacterial agents against positive strains, and their antibacterial activity against negative strains depends upon their concentration. Against positive strains, the WO3/MXene composite’s inhibition zone was at 7 mm, while it became 9 mm upon increasing the concentration. This study proves that WO3, MXene, and the WO3/MXene nanocomposite could be used in biological and environmental applications.

Improvement in visible-light-induced photocatalytic activity of Ag–CeO2 Schottky-type contact heterostructures

This study has widely described the fabrication and performance of a series of Ag–CeO2 Schottky plasmonic photocatalysts under visible light irradiation. A conventional wetness incipient impregnation technique has been utilized to load Ag metal on the surface of CeO2 nanoparticles synthesized by the hydrothermal method. The as-synthesized photocatalysts have been identified using combined characterizations of XRD, FTIR, FESEM, EDS, TEM and UV–Vis DRS. The photocatalytic activity of as-synthesized samples has been investigated in terms of degradation efficiency of methylene blue (MB) as a function of involved operating factors including irradiation photon energy, irradiation time, pH, initial MB concentration, photocatalyst dose and amount of loaded Ag. All of the Ag–CeO2 samples have exhibited higher photocatalytic efficiencies than pure CeO2 with the order of 8%-Ag–CeO2 > 5%-Ag–CeO2 > 2%-Ag–CeO2 > pure CeO2. The enhanced photocatalytic activity has been ascribed to the improved light absorption toward visible irradiation photons due to the surface plasmon resonance, supported by the DRS results. A Schottky scheme photocatalytic mechanism that highlights charge transfer pattern has been developed for photodegradation rate. Photocatalytic process kinetics has been found to obey the pseudo-first-order expression according to the Langmuir–Hinshelwood model.

Enhanced photocatalytic removal of indoor formaldehyde by ternary heterogeneous BiOCl/TiO2/sepiolite composite under solar and visible light

Mineral-based photocatalyst is a promising alternative to eliminate the volatile organic compounds (VOCs) air pollutants because of its low-cost and environmental-friendly merits. Herein, BiOCl/TiO2/sepiolite ternary heterogeneous photocatalyst was synthesized through a facile hydrolysis-precipitation method combining with the calcination crystallization procedure. The gaseous formaldehyde (HCHO) was employed as target pollutant to evaluate the photocatalytic activity of as-synthesized samples. The results indicated that BiOCl/TiO2/sepiolite composite performed much significantly higher adsorption and decomposition capacity for HCHO than pure TiO2, BiOCl and TiO2/BiOCl under solar and visible light. Based on the characterizations and density function theory (DFT) simulation results, the enhanced photocatalytic activity was mainly attributed to the synergistic effect between TiO2/BiOCl and sepiolite through the formation of ternary heterojunction. Such structure could lead to the higher adsorption capacity which can provide more reactive sites, and stronger light response ability as well as faster separation efficiency of photoinduced carriers forming more active radicals during the degradation process. Radical scavenger tests and ESR results indicated that photogenerated holes was the main active species in the reaction system. Overall, this study provides an insight into the design and synthesis of environment-friendly and high-effective heterogeneous composite for practical indoor formaldehyde removal.

Synthesis, characterization and photocatalytic properties of graphene-CdO/SnO2 ternary nanocomposites in visible light

rGO/CdO/SnO2 ternary nanocomposite (GCS) were synthesized using a combination of graphene sheet and CdO/SnO2 nanostructures through the hydrothermal process. The resulting GCS nanocomposite was characterized using XRD, FE-SEM, HR-TEM, and EDS for structural, morphological and compositional studies. The optical characteristics such as UV–vis and PL spectroscopy were used to study the optical properties of the nanocomposite. The XRD analysis showed that CdO and SnO2 nanostructures were crystalline in nature with cubic and orthorhombic phases respectively with the existence of graphene. FESEM images revealed the existence of both cubic and orthorhombic phases of CdO and SnO2 nanostructures respectively. HRTEM study revealed the dispersion of 50–200 nm sized agglomerated nanostructures on the surface of graphene sheets. The analysis of UV–visible & PL spectroscopy shows a considerable decrease in band gap energy from 2.87 to 2.41 eV and improved electron-hole separation respectively. The photocatalytic activity of as-synthesized samples were measured against malachite green (MG) and congo red (CR) dyes. It was found that photocatalytic activity was significantly affected by the ratio of graphene and CdO/SnO2 in the composite. The higher percentage of CdO/SnO2 in the rGO/CdO/SnO2 shows maximum photocatalytic degradation. It occurs due to maximum production and transfer of charge carriers from metal oxide to graphene. It is also found that higher degradation efficiency of MG dye is observed in all the samples of GCS nanocomposite as compared to CR dye.

Novel Z-scheme BiOBr/reduced graphene oxide/protonated g-C3N4 photocatalyst: Synthesis, characterization, visible light photocatalytic activity and mechanism

The novel BiOBr/reduced graphene oxide/protonated g-C3N4 (BiOBr/RGO/pg-C3N4) composites were successfully synthesized by using a facile solvothermal synthesis method. The structure, morphology, optical and electronic properties were explored by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), UV–Vis diffuse reflectance spectroscopy (DRS), and photoelectrochemical measurement. The photocatalytic activities of as-synthesized samples were evaluated by the degradation of Rhodamine B (Rh B) and tetracycline hydrochloride (TC) aqueous solution under visible light irradiation (λ > 420nm). Compared with BiOBr, protonated g-C3N4 (pg-C3N4), BiOBr/pg-C3N4 and RGO/pg-C3N4, BiOBr/RGO/pg-C3N4 composites exhibited higher photocatalytic activity. The total organic carbon (TOC) removal ratios of Rh B and TC over 10% BiOBr/RGO/pg-C3N4 were 88% and 59%, respectively. The excellent photcatalytic performance was investigated by photoluminescence spectroscopy (PL), the radical quenching and electron spin resonance experiments. A Z-scheme charge transfer mechanism was proposed, in which RGO acted as an electron transfer mediator. It was worth pointing out that the closely contacted two-dimensional interface among the BiOBr, the RGO and pg-C3N4 promoted the separation and transfer of photo-generated charge carriers, and thus enhanced the photocatalytic efficiency.

A Novel In-Situ Synthesis and Enhanced Photocatalytic Performance of Z-Scheme Ag/AgI/AgBr/Sulfonated Polystyrene Heterostructure Photocatalyst

Novel Z-scheme Ag/AgI/AgBr/sulfonated polystyrene composite is prepared via ion-exchange followed by light reduction. The photocatalytic activities of as-synthesized samples are evaluated through the degradation of methyl orange (RhB) under visible light irradiation. The Z-scheme Ag/AgI/AgBr/SPs photocatalysts display excellent photocatalytic activity and stability compared with Ag/AgI and Ag/AgBr. The improved photocatalytic activity is mainly due to the combined effects of the Z-scheme structure of Ag/AgI/AgBr/SPs and the strong surface plasmon resonance effect of Ag0 nanoparticles. Moreover, after four successive cycles, the Ag/AgI/AgBr/SPs photocatalysts have no obvious loss of activity for the degradation of RhB, illustrating that the Z-scheme Ag/AgI/AgBr/SPs photocatalysts are rather stable under visible-light irradiation.

In situ synthesis of a nanoplate-like Bi-based heterojunction for photocatalytic degradation of ciprofloxacin

A nanoplate-like Bi-based heterojunction was firstly prepared through in situ formation of Bi2S3 nanocrystals on the surface of BiOBr nanoplates via a facile anion exchange strategy. The as-prepared Bi2S3/BiOBr heterojunctions were carefully characterized by multiple physicochemical techniques. The photocatalytic activity of as-synthesized samples were evaluated by the photodegradation of ciprofloxacin (CIP) under visible-light irradiation (λ>420nm). Compared to the pristine BiOBr, the Bi-based heterojunctions exhibited dramatically enhanced photocatalytic activity towards the CIP degradation in aqueous solution. Moreover, it is found that the 4% Bi2S3 coupled BiOBr heterojunction showed the superior photoreactivity for removal of CIP, which is about 2.8-folds higher than that of pure BiOBr. The significantly improved photoactivity was ascribed to the effective separation of photogenerated electron-hole pair’s between the Bi2S3 and BiOBr. This work highlights a simple approach to design the Bi-based nanocomposites and develops an efficient visible-light-driven heterojunction material for application in antibiotic pollutant purification.

A Facile Hydrothermal Route for Synthesis of ZnS Hollow Spheres with Photocatalytic Degradation of Dyes Under Visible Light

A facile hydrothermal method was employed for the synthesis of ZnS hollow spheres by using thioglycolic acid (TGA) as a capping agent under hydrothermal condition. The obtained products were characterized by X-ray powder diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS). No diffraction peaks from other crystalline forms were detected, the synthesized ZnS hierarchical hollow spheres were relatively pure. The photocatalytic activities of as-synthesized samples were evaluated by the degradation of methyl orange (MO) and rhodamine B (RhB) under the condition of visible-light irradiation. The higher the initial MO and RhB concentrations, the longer it takes to reach the same residual concentration, implying that the apparent rates of MO and RhB degradation decrease with increase in the initial MO and RhB concentration. The increase of photocatalyst dosage from 0.2 to 0.6 g/L results in a sharp increase of the photodegradation efficiency from 68.50 to 92.66% after 180 min of visible-light irradiation for MO degradation, and the increase of photocatalyst dosage from 0.2 to 0.4 g/L results in a distinct increase of the photodegradation efficiency from 65.72 to 90.85% after 180 min of visible-light irradiation for RhB. The elution of intermediates generated in the photocatalytic mineralization of MO and RhB resulted in an increase in total organic carbon (TOC) level, leading to the difference between TOC removal rate and MO and RhB decolorization rates.

Photoredox degradation of different water pollutants (MO, RhB, MB, and Cr(VI)) using Fe–N–S-tri-doped TiO2 nanophotocatalyst prepared by novel chemical method

Fe–N–S-tri-doped TiO2 (FeNS-TiO2) was synthesized by a simple one-step hydrothermal method. The as-synthesized samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). The photocatalytic activities of as-synthesized samples were tested by the oxidation of methyl orange (MO), rhodamine B (RhB), methylene blue (MB) and the reduction of aqueous Cr(VI) under visible-light (λ>420nm) irradiation, and compared with N-dope P25 (N-P25) and the undoped TiO2. Besides, the effects of the coexistence of MO, RhB, and MB on FeNS-TiO2-mediated photocatalytic reduction of aqueous Cr(VI) were also studied. The results indicated FeNS-TiO2 displayed higher visible-light-activated photocatalytic activity than N-P25 and the undoped TiO2. Otherwise, FeNS-TiO2 showed the coexistence of MB enhanced the photocatalytic reduction of Cr(VI), whereas the coexistence of MO and RhB retarded the photocatalytic reduction of Cr(VI) over FeNS-TiO2. Moreover, a possible photocatalytic mechanism is discussed.

Facile synthesis organic–inorganic heterojunctions of HSbO3/g-C3N4 as efficient visible-light-driven photocatalyst for organic degradation

Novel HSbO3/graphitic carbon nitride (HSbO3/g-C3N4) heterojunction photocatalysts were synthesized via a simple method. The prepared HSbO3/g-C3N4 samples were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), ultraviolet–visible diffuse reflection spectroscopy (DRS) and photoluminescence spectroscopy (PL). The photocatalytic activity of as-synthesized samples was evaluated by degrading Rhodamine B (RhB) in aqueous solution under visible-light irradiation. All the HSbO3/g-C3N4 heterojunction photocatalysts showed much higher visible-light photocatalytic activity than those of pure g-C3N4, HSbO3 for the degradation of RhB. The enhanced photocatalytic activity is mainly ascribed to the enhancement of electron–hole separations at the interface of the two semiconductors. This study offers a new class of highly efficient and promising heterojunction photocatalysts.

Facile preparation of Sn-doped BiOCl photocatalyst with enhanced photocatalytic activity for benzoic acid and rhodamine B degradation

A series of Sn-doped BiOCl photocatalysts were successfully synthesized at room temperature via a facile oxidation-reduction method. The as-synthesized products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoemission spectroscopy (XPS), UV–vis diffuse reflectance spectra (DRS) and photoluminescence (PL) emission spectroscopy measurements. The results showed that the as-prepared samples exhibited tetragonal crystal structure, lamellar morphology and band gap energy of 3.12eV and 2.91eV for BiOCl and Sn(10%)-doped BiOCl, respectively. XPS results showed that Sn was in the form of tetra-valence. The photocatalytic activities of as-synthesized samples were evaluated by the degradation of benzoic acid (BA) and rhodamine B (RhB) in an aqueous solution. The results revealed that the Sn doping could enhance the photocatalytic performance of BiOCl and the highest photocatalytic activity was achieved by the Sn(10%)-doped BiOCl, in addition, the optimum dosage of Sn(10%)-doped BiOCl was 0.4mg/L in degrading BA. The improved photocatalytic activity of Sn-doped BiOCl could be attributed to the narrower band gap energy (2.91eV) than pure BiOCl. Furthermore, scavenger experimental results indicated that h+ played the pivotal role in BA photocatalytic degradation. What is more, the as-synthesized Sn(10%)-doped BiOCl photocatalyst exhibited a good stability during the photodegradation of BA and RhB, revealing its promising prospect in the practical application of the treatment of organic wastewaters.

Synthesis, Characterization, and Photocatalytic Activity of N-Doped ZnO/ZnS Composites

The aim of the present study is to enhance photocatalytic performance of ZnO semiconductor by comodification with doping of nonmetal ions and coupling with another semiconductor. Therefore, we synthesized the N-doped ZnO/ZnS photocatalysts via a simple heat-treatment approach using L-cysteine as N and S source in this work. Anthraquinone dye (reactive brilliant blue KNR) is employed as the model contaminants to evaluate the photocatalytic activity of as-synthesized samples under sunlight illumination. The N-doped ZnO/ZnS synthesized by this method shows better photocatalytic activity as compared to that of pure ZnO. The enhanced photocatalytic activity of the N-doped ZnO/ZnS composites may be related to the existence of N doping, ZnS/ZnO heterostructure, and covered abundant carbon species on the photocatalyst surface, which causing high absorption efficiency of light, efficient separation of electron-hole pairs, and quick surface reaction in doped ZnO.