Sunlight Photocatalytic Activity Research Articles

Rice hull-derived biochar with photocatalytic activity for efficient degradation of oxytetracycline in water under sunlight

Photocatalytic degradation is an effective strategy for the removal of environmental pollutants. However, the development of low-cost and high-efficiency photocatalysts continues to present a significant challenge. This work reported the fabrication of a composite photocatalyst directly from waste biomass (rice hulls) in a single step, which efficiently degraded oxytetracycline (OTCs) under sunlight. The morphology, microstructures and photoelectric features of the fabricated materials were subjected to comprehensive investigation using characterization techniques. The results found that the improved photocatalytic activity in sunlight was attributed to the complexation of rice hull-derived biochar and nano-ZnO generated in the preparation, which exhibited favourable adsorption, conductivity characteristics and small bandgap. The photocatalytic efficiency was observed to reach 72.6 % in 120 min under the irradiation of a 100 W xenon lamp. The effect of natural waters, degradation kinetics and degradation TOC analysis were also examined. The dominant agent responsible for the degradation of OTCs was the •O2− radical. Furthermore, the principal photocatalytic degradation pathway of OTCs was identified with the assistance of UHPLC/MS.

Green Synthesis of Uncoated and Olive Leaf Extract-Coated Silver Nanoparticles: Sunlight Photocatalytic, Antiparasitic, and Antifungal Activities.

The circular economy, which attempts to decrease agricultural waste while also improving sustainable development through the production of sustainable products from waste and by-products, is currently one of the main objectives of environmental research. Taking this view, this study used a green approach to synthesize two forms of silver nanoparticles: coated silver nanoparticles with olive leaf extract (Ag-olive) and uncoated pure silver nanoparticles (Ag-pure), which were produced by the calcination of Ag-olive at 550 °C. The extract and the fabricated nanoparticles were characterized by a variety of physicochemical techniques, including high-performance liquid chromatography (HPLC), thermal gravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Adult ticks (Hyalomma dromedarii) (Acari: Ixodidae) were used in this study to evaluate the antiparasitic activity of synthesized nanoparticles and extract. Furthermore, the antifungal activity was evaluated against Aspergillus aculeatus strain N (MW958085), Fuserium oxysporum (MT550034), and Alternaria tenuissiuma (MT550036). In both antiparasitic and antifungal tests, the as-synthesized Ag-olive showed higher inhibition activity than Ag-pure and olive leaf extract. The findings of this research suggest that Ag-olive may be a powerful and eco-friendly antiparasitic and antifungal agent. Ag-pure was also evaluated as a photocatalyst under sunlight for the detoxification of Eri-chrome-black T (EBT), methylene blue (MB), methyl orange (MO), and rhodamine B (RhB).

Low-temperature compositing of graphene to nanodiamonds by thermal reduction of graphene oxide and photocatalytic properties

Graphene has become a research hotspot in the field of composites due to its special structure and excellent properties The common preparation methods of graphene matrix composites include solvent (hydrothermal) method, sol-gel method, chemical reduction method, electrochemical deposition method, etc. Nanodiamond/reduced graphite oxide (rGO) composites are directly synthesized by low-temperature heat treatment with nanodiamonds and graphite oxide (GO) powders as raw materials with the aid of GO thermal reduction at 195 °C. The degradation ability of samples to methylene blue (MB) under simulated sunlight was tested. Results indicated that GO was thermally reduced to graphene at low temperature, and rGO well combined with diamond. After the introduction of GO, the lattice of nanodiamond underwent distortion. Diamond and graphene formed a quasi-core–shell structure, and the interface between them was well bonded. The composite had a large specific surface area (Brunauer–Emmett–Teller value of 93.13 m2/g). The addition of GO enhanced the absorbance of the samples and reduced the bandgap of nanodiamond. When the ratio of nanodiamond to GO was 6:1, the sample exhibited excellent sunlight photocatalytic activity, and MB degradation rate reached 99.8 % within 40 min. The reduction reaction of GO at low temperature promoted its rapid combination with nanodiamonds. This method had the outstanding advantages of simple process, environment friendliness, and easy mass production.

Enhanced dielectric properties of N-doped TiO2 and its photocatalytic activity in sunlight

Enhanced dielectric properties of N-doped TiO2 and its photocatalytic activity in sunlight

Dye Degradation Comparison Studies of Methylene Blue and Methyl Orange by Synthesized Zn Doped Fibrous Wollastonite.

In this study, Zn-doped calcium silicate (Zn-WO) materials were successfully synthesized. As precursors, Ca (OH)2, SiO2, and ZnO were utilized, then the hydrothermal experiment was conducted for 6 hours at 1050°C. In this work, the behavior of two groups of raw materials exposed to isobaric and different temperature circumstances is described. The synthesized sample was examined using XRD, SEM, EDAX, Raman, BET, and UV-Vis spectroscopic techniques to understand the adsorbent's physicochemical characteristics, and the adsorbent's performance was evaluated. The energy band gap of 2.70 eV and 2.62 eV with the surface area calculated by BET of 92.4 m2/g and 112.6 m2/g for Zn-WO-1 and Zn-WO-2 respectively were found in this research. After 150 minutes of Zn-WO-1 and Zn-WO-2, the maximum amount of degradation by absorption under dark and sunlight photocatalytic activity compared with the two synthesized samples, 88.4% and 92.3% of methylene blue and 80.9% and 85.3% of methyl orange, took place.

Eco-Friendly Gelatin–Cerium–Copper Sulphide Nanoparticles for Enhanced Sunlight Photocatalytic Activity

Using a semiconductor catalyst with sunlight can make the photodegradation of pollutants an economically viable process since solar energy is an abundant natural energy source. Solar photocatalysis can provide clean and green eco-friendly technology for the analysis of industrial effluents. Photocatalytic deterioration of the aqueous solution of malachite green oxalate dye (MGO dye) was studied using gelatin–cerium–copper sulphide (Ge-Ce-CuS) nanoparticles under the sunlight source. The nanoparticles were synthesised by a hydrothermal process. The structural properties of the nanoparticles have been characterised by XRD, SEM, EDS, HR-TEM, and XPS. The effects of the initial concentration of dye, dosage of photocatalyst, reaction time, and pH on dye removal efficiency were studied. The mineralisation of MGO dye has been confirmed by chemical oxygen demand (COD) measurements. The reusability of the catalyst was proved. The antibacterial activity has been studied for the synthesised nanoparticles. The higher photocatalytic degradation efficiency of Ge-Ce-CuS is explained by its reduced electron-hole recombination and sunlight activity.

Synthesis of ZnO/MoS2 heterojunction with the green Ag nanoparticles for the efficient sunlight photocatalytic activity

Pristine MoS2 nanosheet/silver nanoparticles (MoS2/Ag NPs) and composites are fabricated via hydrothermal, green synthesis, and chemical methods. Pristine MoS2, Ag, Z/M, and Z/M/Ag nanoparticles and composites are characterized through SEM, FTIR, as well as UV–Vis spectroscopy. The bandgap of materials is reduced effectively which is useful for photocatalytic activity. The photocatalytic decomposition of pharmaceutical drugs in effluent has been researched using metal-oxide or metal-sulfide-based semiconductor nanoparticles as nano-catalysts. The originality of these nano-catalyst substances lies in their relative simplicity of manufacturing, capacity to absorb energy in the UV–visible spectrum, large bandgap, innoxious, and inexpensive. The visible-light photocatalytic activity of Z/M also Z/M/Ag composites were investigated using a test of OTC. Almost degradation of OTC in about 120 min. at different concentrations of composites, Z/M/Ag photocatalyst was attained. This substantial enhancement in the photocatalytic proficiency of Z/M/Ag photo-catalyst below visible light ir-radiation may be ascribed to existence of MoS2 and Ag micro-particles on ZnO micro-particles which significantly improves absorption in an observable scale of the visible range.

Vanadium-doped CuO: Insight into structural, optical, electrical, terahertz, and full-spectrum photocatalytic properties

Aiming to widen the band gap, minimize the charge-carrier recombination, and enhance the transport properties, we reported the first synthesis of high purity vanadium-doped CuO as a promising photocatalyst nanopowder for water purification. Pure CuO and Cu1-xVxO (where x = 0.00, 0.01, 0.03, 0.05, and 0.07 mol) were synthesized by a facile sol-gel technique. The structural investigation performed by both X-ray and selected area electron diffraction patterns evidenced the formation of highly pure monoclinic CuO. The vanadium inclusion caused a noticeable red shift in Bragg's positions. The grain size was estimated by both Debye-Scherrer and Halder-Wagner methods and ranged from 21 to 28 nm. All the vibrational absorption bands disclosed by FTIR measurement are affiliated with monoclinic CuO exhibiting a small shift for V-doped nanopowders. The stoichiometry of the constituent elements (Cu, O, and V) was assured by energy dispersive X-ray analysis (EDX). The presence of agglomeration is the main feature in field emission scanning electron microscope images revealing the nanostructure property of CuO. The band gap energy of Cu0.93V0.07O determined from diffuse reflectance is 1.44 eV which meets exactly the peak of the solar spectrum rendering it a promisingly photocatalytic material. The rise of absorption in the terahertz range as measured by THz time-domain spectroscopy (THz-TDS) established the increase of density of states owing to the inclusion of vanadium. The incorporation of 0.07 mol of V considerably increases the free sunlight photocatalytic activity of CuO for high concentration Congo red pollutant (20 ppm) from 30 to 76% at the same time of 100 min (over 1.53 times as pure CuO)

Improving sunlight-photocatalytic activity of undoped and phosphorus doped MnO2 with activated carbon from bio-waste with nanorods morphology

• P-MnO 2 /AC nanoparticles for photocatalytic activity were synthesized using a hydrothermal technique. • The evenly dispersed AC established good contact with the P-MnO 2 . • Under sunlight irradiation, photocatalytic degradations of MO and RhB dyes are investigated. • The photocatalytic degradation efficiency of the MO and RhB dyes was almost 95%. • P-MnO 2 /AC increased the efficiency of photogenerated electron-hole pair separation and the lifetime of photogenerated electrons substantially . Based on the contributions of phosphorus and Activated carbon (AC) and their composite species are great advances in photocatalytic degradation performance. The evenly distributed Phosphorus and Activated Carbon have good contact with MnO 2 . The activated carbon was made from Manikara zapota peel by chemical activation KOH, and by hydrothermal method P-MnO 2 /AC, nanorods were prepared. The evenly distributed AC has good contact with P-MnO 2 . X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) were used to analyze the samples. Morphology of AC, MnO 2 , and P-MnO 2 /AC was studied using SEM, FESEM, and TEM. UV–visible diffuse reflectance spectroscopy (UV–vis DRS) was used to characterize the bandgap values. The bandgap values of MnO 2 , PMAc (1.0), (3.0), and (5.0) of P-MnO 2 /AC are 2.48 eV, 1.99 eV, 1.76 eV, and 1.62 eV, respectively. They confirmed that increasing the quantity of AC reduced the bandgap values. The photocatalytic efficiency of the MnO 2 and P-MnO 2 /AC samples are studied using the photodegradation of MO and RhB dyes under sunlight. The best photocatalytic degradation performance was obtained by P-MnO 2 /AC for MO and RhB dye, which are excellent degradation efficiency of 96.31 % and 97.57 %, respectively. Furthermore, within 180 min, the optimal TOC removal approached 56.4, 80.3, and 87 % for MnO 2 , PMAc (5.0) MO, and RhB, respectively. Moreover, Trapping experiments were characterized by RhB dye PMAc (5.0) of P-MnO 2 /AC. In addition, IPA had the smallest degrading efficiency (11.46 %) with • OH radicals haveing a substantial role. Furthermore, PMAc (5.0) of P-MnO 2 /AC doping was successfully used for five photodegradation cycles with no notable change in activity or crystalline properties by RhB dye. Furthermore, the mechanism of catalytic performance enhancement was addressed. These nanoparticle materials could be used in high-performance photocatalytic applications.

Novel Amapá latex-mediated synthesis of defective α-Fe2O3 nanoparticles with enhanced ferromagnetism and sunlight photocatalytic activity

Iron oxide (α-Fe2O3) nanoparticles were synthesized using the latex of the Parahancornia amapa tree (Amapá latex) as an ecofriendly chelating agent. Raman, XRD, and Rietveld refinements analysis confirmed that all samples are single-phase with crystallite size in the range of 64–93 nm. SEM images showed that the volume of Amapá-latex used for synthesis plays an important role in forming nanoparticles with different morphologies and particle sizes of about 65–110 nm. PL spectra revealed the presence of ligand-to-metal charge-transfer transition (wide emission band positioned at ∼ 400 nm) and coexistence of both Oi and VO defects in the α-Fe2O3 nanoparticles. The highest remanent magnetization (∼0.09 μB/f.u.) and decolorization (94%) of MB dye were majority driven by the Oi and VO structural defects. A 33% TOC removal around 1h of the degradation process, which further increased to 70% after 6h, confirmed that MB molecules were cleaved and broken. These findings reveal that α-Fe2O3 nanoparticles synthesized by our Amapá latex-mediated route proved to be efficient for the obtention of α-Fe2O3 nanostructures with the potential to be used for the affordable treatment of dye-contaminated wastewater.

Fabrication of Au-Ag@TiO2 ternary core-shell nanostructures with enhanced sunlight photocatalytic activity

In this work, Au loaded Ag@TiO2 ternary core-shell structures (Au-Ag@TiO2) were synthesized by a two-step method in mild conditions. The Ag nanoparticles existed as cores in the inner layer and the Au nanoparticles decorated in the outer layer. The greatly improved sunlight absorption performance is due to the LSPR of Au nanoparticles, while the Ag nanoparticles mainly serve as the electron traps to prevent charge recombination. The photocatalytic activity of the as-prepared Au-Ag@TiO2 was evaluated by photo-degradation of MO under artificial sunlight illumination. And the 1.5%Au-Ag@TiO2 ternary core-shell particles showed the highest photo degradation efficiency, which was about 4 and 1.6 times higher than that of the pristine TiO2 and Ag@TiO2 particles. The main active species that contributed to the reaction were proved to be holes (h+) and superoxide anions (•O2−). These proposed Au-Ag@TiO2 ternary core-shell particles are promising for potential applications in environmental remediation and energy conversion.

Glucose-mediated one-pot hydrothermal synthesis of hollow magnesium oxide-zinc oxide (MgO-ZnO) microspheres with enhanced natural sunlight photocatalytic activity.

Glucose -mediated one-pot hydrothermal method has been utilized to synthesize hollow spherical MgO-ZnO (xMgO-(1-x)ZnO, x = 0, 0.2, 0.4, 0.6) microstructures which are highly efficient in high-energy ultraviolet (UV) region of natural sunlight. In this process, glucose formed roundish spheres, and simultaneously metal precursors were coated on that spheres during the hydrothermal reaction. X-ray diffraction analysis (XRD) supports the formation of highly crystalline wurtzite structure of MgO-ZnO for Mg loading less than 20%. Higher concentration of Mg produces wurtzite hexagonal ZnO and cubic MgO in the composites. The widening in band gap energy of synthesized MgO-ZnO microspheres compared to ZnO was analyzed by UV-visible diffuse reflectance spectroscopy (UV-DRS) result. Brunauer-Emmett-Teller (BET) surface area analysis showed that with the increase in Mg loading, the specific surface area increases up to 14.27 times as compared to pristine ZnO. The synthesized catalysts were used as an efficient photocatalyst towards the degradation of rhodamine B (RhB), methylene blue (MB), and phenol under natural solar irradiation. Results illustrated that MB and RhB dye solutions were 100% degraded by 0.6 MgO-ZnO in 100min and 150min, respectively, whereas pure ZnO samples showed only 65% and 79% degradation. Also, for phenol solution, 0.6 MgO-ZnO showed enhanced degradation efficiency of 72% in 240min in comparison with 58% degradation shown by ZnO. Additionally, the MgO-ZnO catalysts were stable and showed excellent degradation efficiency up to four consecutive cycles which open a new direction towards potential industrial applications. Hence, the novelty of the current work is to prepare hollow MgO-ZnO microspheres by a single-step hydrothermal process where separate carbon template preparation is not required and to utilize these hollow microspheres as a highly efficient photocatalyst by harnessing the high-energy UV fraction of natural sunlight.

A simple and green photoreduction approach for synthesis of Au/g-C3N4 hybrid nanocomposites with high solar light photocatalytic activity

In this study, we developed a green and easy to scale up approach for producing Au/g-C3N4 (Au/GCN) hybrid plasmonic photocatalyst without using the chemical reducing agents via the growing of Au nanoparticles (Au NPs) on the surface of GCN nanosheets under the photo-reduction of ultraviolet (UV)-radiation. Different characterization techniques were conducted for investigating the structure, morphology, surface chemistry and optical properties of the as-prepared catalysts. The scanning electron microscope image shows that the homogeneous Au NPs anchored on the surface of the GCN nanosheet increased with the UV illumination time. The x-ray photoelectron spectroscopy results prove the coexistence of GCN nanosheets with heptazine heterocyclic ring (C6N7) units and Au NPs in the Au/GCN. The photoluminescence intensity decreased sharply with the time of UV irradiation, indicating that the recombination rate of photogenerated electron–hole recombination decreased. The photocatalytic activity of the hybrid catalysts was evaluated by degrading rhodamine B (RhB) under simulated sunlight irradiation. The results show that the Au/GCN photocatalyst exhibits superior sunlight photocatalytic activity than that of bare GCN. The 6 h irradiated fabricating sample exhibited the strongest photocatalytic activity, completely decomposing the 10 ppm RhB in 30 min of irradiation. This report can provide the design of a simple and green synthesis method for the highly active Au/GCN photocatalyst.

Enhanced sunlight photocatalytic activity and biosafety of marine-driven synthesized cerium oxide nanoparticles

This contribution presents the biosynthesis, physiochemical properties, toxicity and photocatalytic activity of biogenic CeO2 NPs using, for the first time, marine oyster extract as an effective and rich source of bioreducing and capping/stabilizing agents in a one-pot recipe. CeO2 NPs formation was initially confirmed through the color change from light green to pale yellow and subsequently, their corresponding absorption peak was spectroscopically determined at 310 nm with an optical band-gap of 4.67 eV using the DR-UV technique. Further, XRD and Raman analyses indicated that nanoceria possessed face-centered cubic arrangements without any impurities, having an average crystallite size of 10 nm. TEM and SEM results revealed that biogenic CeO2 NPs was approximately spherical in shape with a median particle size of 15 ± 1 nm. The presence of various bioorganic substances on the surface of nanoparticles was deduced by FTIR and TGA results. It is found that marine-based nanoceria shows no cytotoxic effect on the normal cell, thus indicating their enhanced biocompatibility and biosafety to living organisms. Environmentally, due to energy band gap, visible light-activated CeO2 nanocatalyst revealed superior photocatalytic performance on degradation of methylene blue pollutant with removal rate of 99%. Owing to the simplicity, cost-effectiveness, and environmentally friendly nature, this novel marine biosynthetic route paves the way for prospective applications of nanoparticles in various areas.

Density functional theory and experimental investigations on sunlight photocatalytic activity of Co-doped MoO3 nanobelts enabling tetracycline removal

This work reports one-dimensional Co-doped MoO3 nanobelts for photodegradation of tetracycline under simulated sunlight irradiation for the first time. Benefiting from the synergistic effect between the optimized structure of material morphology and chemical doping, 3%Co-doped MoO3 nanobelts exhibit even better photocatalytic activity compared to other samples, highlighting the structure-specific reactivity. The doping introduction can lead to impurity level, efficiently promoting the separation and transportation of photogenerated electron-hole pairs. Moreover, the electronic structure of photocatalysts was investigated by density functional theory as qualitative confirmation for experiments, and the photocatalytic mechanism was proposed in detail.

Bi2WO6\u2013BiOCl heterostructure with enhanced photocatalytic activity for efficient degradation of oxytetracycline

The application of BiOCl in photocatalysis has been restricted by its low utilization of solar energy and fast recombination of charge carriers. In this study, zero-dimensional (0D) Bi2WO6 nanoparticles/two-dimensional (2D) layered BiOCl heterojunction composite was successfully constructed by facile hydrothermal and solvothermal methods. The most favorable sunlight photocatalytic activity was achieved for the as-prepared Bi2WO6–BiOCl composites with a ratio of 1%. The photocatalytic rate and mineralization efficiency of one typical antibiotic (i.e., oxytetracycline) over 1% Bi2WO6–BiOCl was about 2.7 and 5.3 times as high as that of BiOCl. Both experimental characterizations and density functional theory (DFT) calculations confirmed that the excellent photocatalytic performance mainly arised from the effective charge separation along the Bi2WO6 and BiOCl heterojunction interface. The effective electron transfer was driven by the internal electric field at the interfacial junction. In addition, 1% Bi2WO6–BiOCl exhibited excellent stability, and no apparent deactivation was observed after 4 test cycles. Therefore, the 0D/2D Bi2WO6–BiOCl heterojunction showed a great potential for the photocatalytic degradation of emerging organic pollutants.

Sodium Dodecyl Benzene Sulfonate-assisted Synthesis and Natural Sunlight Photocatalytic Activity of La Bismuthate Nanorods

Background: Removal of the organic pollutants using the photo-catalysts by the photocatalytic treatment process under natural sunlight irradiation has attracted great attention owing to the complete destruction of the organic pollutants. The La bismuthate nanorods possess good photocatalytic performance for the removal of the methylene orange (MO) under the sunlight irradiation. Objective: The aim is to synthesize La bismuthate nanorods by hydrothermal method and research the photocatalytic performance of the La bismuthate nanorods for MO degradation under sunlight irradiation. Methods: La bismuthate nanorods have been synthesized by a simple sodium dodecyl benzene sulfonate (SDBS)-assisted hydrothermal method using sodium bismuthate and La acetate as the starting materials. The obtained La bismuthate products were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy and solid UV-vis diffuse reflectance spectrum. Results: With different SDBS concentration, hydrothermal temperature and reaction time, different morphologies of the La bismuthate products were obtained. XRD analysis shows that the La bismuthate nanorods obtained from 180°C for 24 h with 5wt.% SDBS are composed of orthorhombic La1.08Bi0.92O3.03 phase. Electron microscopy observations show that the La bismuthate nanorods with flat tips have the length of longer than 10 μm and diameter of about 20-100 nm, respectively. The morphology and structure of the products are closely related to the SDBS concentration, hydrothermal temperature and reaction time. Solid UV-vis diffuse reflectance spectrum shows that the band gap of the La bismuthate nanorods is 2.37 eV. The La bismuthate nanorods show good photocatalytic performance for the degradation of MO under the sunlight irradiation. MO solution with the concentration of 10 mg.L-1 can be totally removed by 10 mg La bismuthate nanorods in 10 mL MO aqueous solution under sunlight irradiation for 6 h. Conclusion: The photocatalytic performance for the removal of MO is dependent on the sunlight irradiation time and dosage of the La bismuthate nanorods. The La bismuthate nanorods exhibit great potential for the removal of organic pollutants.

Influence of pH variation on CuWO4, CuWO4/WO3 and CuWO4/CuO structures stabilization: study of the photocatalytic properties under sunlight

In this work, the reaction pH range (from 2 to 10) was used to study the stabilization of the CuWO4 phase in the presence of polyvinylpyrrolidone surfactant synthesized by the sonochemical method. The powders were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, field emission scanning electron microscopy (FE-SEM), nitrogen adsorption and desorption using the Brunauer–Emmett–Teller methodology and ultraviolet–visible spectroscopy (UV–Vis). The photocatalytic activity was studied against MB dye under sunlight and CuWO4 powders were tested at 5 reuse cycles. Diffractograms indicated that syntheses at pH 2 and 4 generate WO3/CuWO4 heterostructures, while reaction pH at 8 and 10 generate CuO/CuWO4 heterostructures and at pH 6 generates pure CuWO4. FE-SEM images indicated semispherical morphology for CuWO4, nanoplate morphology for CuO, and large particles without definite form for WO3 powders. The scavenger's methodology indicates that hydroxyl radicals are the main responsible for the photodegradation of methylene blue in all samples. Also, it indicates that the formation of the WO3/CuWO4 and CuO/CuWO4 heterostructures increase the e−/h+ pair recombination rate, reducing the photocatalytic activity in sunlight.

Superior sunlight photocatalytic of N/La codoped ZnO nanostructures synthesized using different chelating agents

N/La codoped ZnO exhibited high sunlight activity, good reusability and rapid photodegradation for Congo red, malachite green and methylene blue dyes. Pure and N/La codoped ZnO were synthesized by sol gel using different chelating agents. All XRD patterns are fully indexed to hexagonal wurtzite structure of ZnO. The XRD peak shift and the increases in unit cell volume confirm the effective incorporation of N/La ions into ZnO. N/La blend extended the absorption ability of ZnO nanostructures to visible light region. Pure and N/La codoped ZnO synthesized by citric acid showed homogenous spherical nanoparticles distribution. Oxalic acid induced the formation of nanosheets and fine nanoparticles in N/La codoped ZnO. The adsorption capacity of pure and N/La codoped ZnO powders toward CR, MG and MB was less than 8%. The degradation of CR, MG and MB dyes under sunlight without catalyst is very weak. N/La codoped ZnO nanostructures exhibited superior sunlight photocatalytic activity for organic dyes degradation. N/La codoped ZnO–C and N/La codoped ZnO–O samples displayed remarkable photodegradation activities within 92–97% for CR, MG and MB in 60 min. N/La codoped ZnO–C showed a perfect photostability and reusability for four cycles. N and La enhance the charge carriers’ separation and the visible light absorption in ZnO which increase the photocatalytic activity.

Design of TiO2 nanocrystals with enhanced sunlight photocatalytic activity by exploring calcining conditions

As a promising inorganic semiconductor photocatalyst, TiO2 has been widespread concerned since 1972. However, its practical application is limited due to its low efficiency for utilizing solar light and rapid recombination of photo-generated charges. Here, we report a way to solve these problems by calcining TiO2 samples under different conditions. It was found that the catalytic performance of TiO2 catalysts was closely related to calcination temperature and calcination atmosphere. The XRD, Raman spectra, BET, UV–vis spectra, SEM and TG-DTA investigations of the catalysts revealed that the crystal structure of TiO2, the specific surface area, and abundant oxygen vacancies were the primary factors influencing the performance of TiO2 catalysts. Consequently, the TiO2 nanocrystal calcined in a nitrogen/hydrogen mixed atmosphere at 300 °C for 3 h exhibited higher catalytic activity than others. These results demonstrated that annealing conditions can play an important role in catalyst activity.