Strong Photocatalytic Activity Research Articles

Ultrasound-assisted synthesis of metal organic framework for the photocatalytic reduction of 4-nitrophenol under direct sunlight

In this study, the metal organic framework MOF [Zn(BDC)(DMF)] crystal was synthesized via ultrasonic irradiation and solvothermal method. The synthesized MOF [Zn(BDC)(DMF)] crystal was characterized by PXRD, FTIR, FESEM-EDX, TGA, UV-DRS and BET. The catalytic activity of MOF [Zn(BDC)(DMF)] was investigated by 4-nitrophenol (4-NP) degradation under direct sunlight irradiation. The influence of various degradation parameters such as initial 4-NP concentration, dosage, pH and H2O2 concentration were investigated. The results indicated that the synthesized MOF [Zn(BDC)(DMF)] exhibited strong photocatalytic activity in the presence of NaBH4 under sunlight irradiation and the reduction of 4-NP to 4-aminophenol (4-AP) completed within 10 min. The study provides the synthesized MOF [Zn(BDC)(DMF)] crystal can be used as a high performance catalyst for the treatment of dyes in wastewater.

Synthesis of graphene oxide/Bi2O3 based nanohybrids by organic electrolyte-assisted coprecipitation method

ABSTRACTA versatile approach was developed to synthesize graphene oxide/Bi2O3 nanohybrids by organic electrolyte-assisted coprecipitation method. The structure, morphology and photocatalytic property of GO/Bi2O3 hybrids were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and UV-vis spectrophotometer, respectively. Experimental results showed that the tadpole-like MoO2-Bi2O3 hybrids and WO3-Bi2O3 nanorods were covered on the graphene sheets, respectively. Furthermore, the resultant GO/Bi2O3 hybrids possessed strong adsorption ability and high photocatalytic activity for Rhodamine B (RhB).

Photophysical and Photocatalytic Properties of BiSnSbO₆ under Visible Light Irradiation.

BiSnSbO6 with strong photocatalytic activity was first fabricated by a high-temperature, solid-state sintering method. The resulting BiSnSbO6 was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (DRS) and X-ray photoelectron spectroscopy (XPS). The results showed that BiSnSbO6, with a pyrochlore structure and a cubic crystal system by a space group Fd3m, was well crystallized. The lattice parameter or the band gap of BiSnSbO6 was 10.234594 Å or 2.83 eV. Compared with N-doped TiO2, BiSnSbO6 showed higher photocatalytic activity in the degradation of benzotriazole and rhodamine B. The apparent first-order rate constant for BiSnSbO6 in the degradation of benzotriazole and rhodamine B was 0.0182 min−1 and 0.0147 min−1, respectively. On the basis of the scavenger experiment, during the photocatalytic process, the main active species were arranged in order of increasing photodegradation rate: •OH < •O2− < h+. The removal rate of benzotriazole or rhodamine B was approximately estimated to be 100% with BiSnSbO6 as a photocatalyst after 200 min visible-light irradiation. Plentiful CO2 produced by the experiment indicated that benzotriazole or rhodamine B was continuously mineralized during the photocatalytic process. Finally, the possible photodegradation pathways of benzotriazole and rhodamine B were deduced.

Facile synthesis of magnetic Fe3O4@BiOI@AgI for water decontamination with visible light irradiation: Different mechanisms for different organic pollutants degradation and bacterial disinfection

Magnetic Fe3O4@BiOI@AgI (FBA) spheres were synthesized through a multi-step process. The fabricated photocatalysts were characterized by different techniques. To testify the visible light driven photocatalytic activity of FBA, Rhodamine B and Bisphenol A were chosen as model common and emerging organic contaminants, respectively. While, gram-negative strain Escherichia coli was selected as model waterborne bacteria. The results showed that under visible light irradiation, FBA contained strong photocatalytic degradation capacity towards both RhB and BPA. Moreover, FBA was also found to exhibit excellent disinfection activity towards E. coli. The photocatalytic mechanisms for different pollutants by FBA were determined and found to vary for different pollutants. Specifically, scavenger experiments, degradation intermediates determination, as well as theoretical density functional theory (DFT) analysis showed that RhB and BPA were degraded via photosensitization (dominated by e- and ·O2−) and direct photocatalytic oxidation (contributed by h+, e- and ·O2−), respectively. Whereas, E. coli cells yet were found to be inactivated by the generation of e- and ·O2− rather than by the released Ag+. Since it contained superparamagnetic property, FBA could be easily separated from the reaction suspension after use. Due to the excellent photo stability, FBA exhibited strong photocatalytic activity in the fourth reused recycle. Therefore, FBA could serve as a promising alternative for water purification.

Effects of different alkali metal ions on morphology and photocatalysis properties of ZnO crystals via hydrothermal method

With the precursor solution prepared by ZnSO4·7H2O and MOH (M = Li, Na or K), ZnO nanocrystals single doped with Li, Na, K and codoped with Na and K were prepared via a simple hydrothermal method. Their morphologies and structures were characterized by SEM, XRD, ICP, XPS and ultraviolet-visible spectrophotometer methods. It is found that the crystal morphology changes from the short bar shape to the long strip shape; Li+ is likely easier than Na+ and K+ to enter into the lattice to replace Zn2+ and inhibits the growth of positive polar plane while promotes the growth of negative one of ZnO in hydrothermal environment, leading to the morphology of short bars; K+ is easier than Li+ and Na+ to promote the two-dimensional nucleation and accelerate the axial growth of ZnO, leading to the morphology of long strips; Na+ and K+ have the obvious synergistic effect to facilitate the access to the lattice of ZnO. Experimental result of photocatalytic degradation of methylene blue shows that the ratio I of intensitiy of X-ray diffraction peak for (002) plane to that of (100) plane can reflect the relative area proportion of plane (002) with strong photocatalytic activity, and the photocatalytic effect may be better if the value of I is larger.

Leaf-templated synthesis of hierarchical AgCl-Ag-ZnO composites with enhanced visible-light photocatalytic activity

In this paper, poplar leaf is used as a template to synthesize hierarchical AgCl-Ag-ZnO composites via a calcination method. Zn(NO3)2 and AgNO3 are selected as precursors. During the calcination of the templates, Zn2+ ions react with oxygen to produce ZnO nanoparticles (NPs), Cl− ions in leaf cells combine with the external Ag+ ions to form AgCl, and Ag+ ions are reduced by reducing agents in leaf to Ag NPs. The morphology, structure and visible-light response of the as-prepared hierarchical AgCl-Ag-ZnO composites are determined. The composites exhibit a strong photocatalytic activity toward the degradation of Rhodamine B (RhB) under visible-light irradiation. The AgCl-Ag-ZnO composites display an enhanced photocatalytic activity, compared with the leaf-templated AgCl-Ag and ZnO. A photocatalytic mechanism is proposed, based on the efficient separation of photoexcited electron-hole pairs due to the surface plasmon resonance (SPR) effect of metal Ag.

Preparation of Ag@AgCl/g-C3N4/TiO2 porous ceramic films with enhanced photocatalysis performance and self-cleaning effect

We report a novel method to prepare translucent and stable Ag@AgCl/g-C3N4/TiO2 ceramic films having strong photocatalytic activities and self-cleaning capabilities under light irradiation. Colloidal silica was used as an inorganic binder and P25 TiO2 was added as a hydrophilicity enhancer without which a smooth coating was not achievable. Ag@AgCl of particle size around 30 nm, was synthesized by in-situ oxidation of nano-silver particles in porous g-C3N4/TiO2 films. Optimal conditions for Ag@AgCl/g-C3N4/TiO2 preparation in terms of strongest photocatalysis were established by tests on Rhodamine B degradation under visible and full spectral irradiations. A good adhesion strength of the porous films on glass substrate was achieved. Stability and reusability of the films were assessed by cycling tests. Possible photocatalytic mechanisms are proposed based on the basis of trapping experiments. Systematic characterization of the film suggests that the in-situ oxidation is an effective and practical method to produce nanoscale Ag@AgCl.

In Situ SERS Monitoring the Visible Light Photocatalytic Degradation of Nile Blue on Ag@AgCl Single Hollow Cube as a Microreactor

AbstractReaction monitoring and mechanism study for catalytic processes are important for catalyst design and application, and surface enhanced Raman scattering (SERS) is a promising tool in this area because of its high sensitivity and non‐destructive detection mode. Here a new strategy was proposed for fabricating a micro‐scale Ag@AgCl hollow cube as both a uniform and active photocatalyst and a SERS sensing framework. It was confirmed that the stable micro cube was able to be used as a single particle based platform for SERS monitoring of the photocatalytic reaction on it. This bifunctional material hold both strong SERS enhancement ability (enhancement factor up to 2.4×108) and high photocatalytic activity. Such a micro‐reactor was successfully applied to in situ track the photocatalytic degradation reaction of Nile blue (NB). The SERS monitoring data showed that this photocatalytic reaction apparently followed a pseudo‐first‐order reaction model in kinetics with a rate constant of 0.557 min−1. By looking into the molecular finger‐print information acquired from SERS monitoring, the pathways of the photocatalytic degradation of NB were clarified, which involved the cleavages of two backbones in NB hetero‐ring and the direct oxidation cleavage of naphthalene, as supported by the liquid chromatograph‐mass spectroscopic analysis of the degradation intermediates.

Bi60In2O93 Nanoparticles: Photocatalytic Activity Investigation

Objective: Synthesis and characterization of bismuth indium oxide (Bi60In2O93) nanoparticles and their evaluation as new visible lightsensitive photocatalysts. Methods: Synthesis was achieved using a simple hydrothermal method at low temperature and the crystal structures and morphology of the prepared Bi60In2O93 nanoparticles were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Optical properties of the nanoparticles were measured by UV-visible spectroscopy and photocatalytic activity was tested by measuring their effects on rhodamine-B degradation under UVvisible and visible light. Results: The prepared samples had high crystallinity and were tetragonal. Bi60In2O93 nanoparticles exhibited strong photocatalytic activity under simulated sunlight. Nanoparticles prepared from a Bi:In mole ratio of 12:1 had the smallest size (~75 nm in diameter) and were the most uniform with good spherical morphology. These particles showed the strongest photocatalytic activity, including activity in the visible region. The possible mechanism for activity enhancement of Bi60In2O93 nanoparticles compared with Bi2O3 was investigated. The enhanced degradation of rhodamine-B, which is promoted by dye sensitization, is related to the higher crystallinity, unique tunnel structure, narrower band gap and special electron structure of the Bi60In2O93 nanoparticles. Conclusion: Bi60In2O93 nanoparticles show good promise as visible light-sensitive photocatalysts and for semiconductor development.

Synthesis and characterization of metal organic framework-based photocatalyst and membrane for carbon dioxide conversion

The present work is an approach to study the photocatalytic conversion of carbon dioxide (CO2) to methanol by using a novel MOF-based catalyst. A copper-based metal organic framework called Cu3BTC2 where (BTC = benzene-1, 3, 5-tricarboxylate) was synthesized successfully by solvothermal and co-ordination modulation method. The MOF thus obtained exhibited a large surface area. It was further utilized as one of the reactants for the synthesis of an MOF-based photocatalyst containing TiO2. This photocatalyst, TiO2@Cu3BTC2, was obtained by the hydrolysis of Titanium (IV) isopropoxide under solvothermal conditions. The prepared MOF was then characterized by X-ray diffraction (XRD), Thermo-gravimetric analysis (TGA) and Brunauer–Emmett–Teller (BET) techniques. It was noted that TiO2@Cu3BTC2 exhibits strong photocatalytic activity in comparison with TiO2 nanoparticles and this modified form of the photocatalyst could be used in the conversion of carbon dioxide to methanol using visible light as a source of irradiation. Additionally, an MOF-based membrane was synthesized using soil and first dip coating procedure. After characterization of the membrane, it was observed that the nucleation density of MOF directly on a clay-based support was very low. Treatment of membrane with alumina could increase the coverage of MOF particles as it would provide a better-activated surface.

Microstructures and photocatalytic properties of ZnO films fabricated by Zn electrodeposition and heat treatment

Nanostructured zinc oxide (ZnO) thin films were synthesized via an electrodeposition and subsequent heat treatment method. Using the annealing temperatures ranging from 300°C to 600°C, the films develop a variation of microstructures of distinct properties and characteristics. Photocatalytic activities of the ZnO films were studied from photodegradation of methylene blue dye under UV light. Overall, the ZnO films show good photodegradation efficiency and photostabilization. The ZnO film fabricated at 500°C particularly exhibits relatively high surface area and the strongest photocatalytic activity, which is fairly stable after successive reaction cycles.

Self-induced preparation of Ti3O5 nanorods by chemical vapor deposition

The single crystalline monoclinic Ti3O5 nanorods were successfully synthesized on Ti5Si3 powder by self-induced atmospheric pressure chemical vapor deposition (APCVD) method using SiH4, TiCl4, and O2 as the precursors. The results showed that the smooth and straight nanorods were obtained on Ti5Si3 particles heating at 800 °C for 90 min using 20 SCCM (SCCM denotes cubic centimeter per minute at STP (standard temperature and pressure)) O2. The length and diameters of nanorods was about 500 nm and 20–40 nm, respectively. The Ti3O5 nanorods were grown on Ti5Si3 particles from the bottom and then the tip was pushed upwards. The growth process results indicated that the self-induced growth was the main mechanism for nanorods formation. Meanwhile, the Ti3O5 nanorods exhibited high density and large specific surface with stronger photocatalytic activity. The intensity of absorption peak of methylene blue solution decreased from 0.69 to 0.09 with higher degradation rate of 80% under conditions of Ti3O5 nanorods. Thus, the novel Ti3O5 nanorods have great potential application for pollution photocatalytic degradation.

Significantly enhanced photocatalytic performance of zinc oxide via bismuth oxybromide hybridization and the mechanism study

A highly efficient and stable ZnO–BiOBr composite photocatalyst was prepared by a facile one-pot solvothermal method. A variety of sophisticated techniques such as X-ray diffraction (XRD), X-ray photoemission spectroscopy (XPS), UV–Vis diffuse reflectance spectra, photoluminescence spectra and photoelectrochemical measurement, and so on were employed to characterize the materials. The as-prepared ZnO–BiOBr nanocrystalline showed strong photocatalytic activity for decomposition of methylene blue (MB), Orange II and biphenol A (BPA) under simulated visible light illumination. The possible working principle for the superior photocatalytic properties and reusability of the ZnO–BiOBr hybrid was surveyed to disclose contributions of various effects for the photoactivity enhancement. It was pointed out that *OH and holes take priority over ∙O2 − radicals in serving as the main oxidant in the reaction system. The experimental results indicated that the ZnO–BiOBr composite is highly photostable and valuable for real environmental applications.

In Situ Photoactivated Plasmonic Ag3PO4@silver as a Stable Catalyst With Enhanced Photocatalytic Activity Under Visible Light

Silver orthophosphate (Ag3PO4) had been reported as an excellent candidate to split water or decompose pollutants with high efficiency in visible light region, yet is not stable due to the reduction of silver ion. In this work, an easy-fabricated method (in situ photoinduced reduction) was provided to enhance the stability of Ag3PO4 for its possible application as a visible-light sensitive photocatalyst. The as-prepared samples were characterized by X-ray diffraction (XRD), UV-vis diffuse reflectance spectra, photoluminescence spectra (PL) and Photoelectrochemical measurements. The Ag3PO4/Ag photocatalysts showed strong photocatalytic activity for decomposition of RhB dye or phenol-X-3B mixture under visible light irradiation (λ> 420 nm) and can be used repeatedly. The possible mechanism for the enhanced photocatalytic properties of the Ag3PO4/Ag hybrid was also discussed. It was found that •OH and holes take priority over •O2- radicals in serving as the main oxidant in the Ag3PO4/Ag photocatalytic system. Especially, the experimental results indicate that the surface plasmon resonance of Ag nanoparticles and a large negative charge of PO43- ions as well as high separation efficiency of e--h+ pairs, facilitated the enhancement of the photocatalytic activity of the Ag3PO4/Ag composite. The results indicated that Ag3PO4/Ag is an efficient and stable visible-light-driven photocatalyst.

Plasma electrochemical synthesis of cuprous oxide nanoparticles and their visible-light photocatalytic effect

A plasma electrochemical method is used to synthesize cuprous oxide nanoparticles (Cu2O NPs). In this system, a gaseous discharge plasma is used to replace the usual solid electrode in a conventional electrodeposition, and Cu2+ ions are released from anodic dissolution and take a form of Cu2(OH)2+ in the solution. The Cu2(OH)2+ moves to the cathode reaction zone and then is reduced to the Cu2O monomer by reductants generated from the plasma-liquid interactions. Consequently, Cu2O NPs are formed in the solution by the combination of Cu2O monomers. The results indicate that the morphology and Cu valence in the nanoparticles are tuned by the added surfactant of glucose or ascorbic acid. Moreover, the Cu2O NPs synthesized with a suitable concentration of ascorbic acid demonstrate strong visible light photocatalytic activity on the methyl orange degradation.

Photocatalytic Degradation of Acid Orange II Using Activated Carbon Fiber-Supported Cobalt Phthalocyanine Coupled with Hydrogen Peroxide

Activated carbon fiber-supported cobalt phthalocyanine photocatalyst (Co-TDTAPc-F) was prepared in this study, and its performance for dye wastewater decoloration was investigated, and Acid Orange II (AO7) was selected as the target pollutant. The morphology analysis of Co-TDTAPc-F was conducted, and the effects of catalyst loading, H2O2 addition, solution pH, and catalyst reuse on AO7 decoloration efficiency were evaluated. The results showed that AO7 decoloration efficiency increased by 23.2% during the Co-TDTAPc-F photocatalytic process as compared with solely Co-TDTAPc-F adsorption, and the decoloration process was fitted by pseudo first-order reaction. The increase of catalyst loading and H2O2 content both benefitted AO7 decoloration. Strong photocatalytic activities were observed at both acidic and alkaline conditions; however, total organic carbon (TOC) removal efficiency decreased with the increase of solution pH. Strong photocatalytic activity was still observed after four times reuse. The mechanisms of AO7 photocatalytic decomposition by Co-TDTAPc-F were proposed.

High visible light intercalated nanophotocatalyst (PbS-CdS/Ti6O13) synthesized by ultrasound: Photocatalytic activity, photocorrosion resistance and degradation mechanism

Abstract In this study, the photocatalytic activity of the PbS-CdS/Ti6O13 nanocomposite prepared by sono-intercalation method was evaluated by the degradation of Reactive Black 5 (RB5) as a water pollutant under sunlight irradiation. Strong photocatalytic activity was observed due to the improved light harvesting property of photocatalyst, significant decrease in bandgap energies and heterogeneous electron transfer from CdS and PbS as a guest to K2Ti6O13 as a host. The RB5 concentrations in the solution and on the surface of PbS-CdS/Ti6O13 nanocomposite were measured during the experiment. The effects of some important parameters such as ultrasonic amplitude and initial composite ratio were studied in the synthesis of nanocomposite. The activity of synthesized nanocomposites on the dye degradation was evaluated and the stability and photocorrosion resistance of the catalyst were studied in this work too. In addition, the mechanism of separation of the photogenerated electrons and holes in the PbS-CdS/Ti6O13 nanocomposite was investigated. The responsible superior active species for the photodegradation activity were explored and a possible mechanism was suggested.

Sapium sebiferum leaf extract mediated synthesis of palladium nanoparticles and in vitro investigation of their bacterial and photocatalytic activities

There is a growing need to introduce eco-friendly and sustainable procedures for the synthesis of metal nanoparticles that include a mild reaction conditions, simple reaction setup, use of nontoxic medium such as water and plant extract, cost effectiveness as well as greater efficiency for biomedical and catalytic applications. For this purpose, small and highly dispersed palladium nanoparticles (PdNPs) were prepared by eco-friendly and cost effective green method using water soluble leaf extract of Sapium sebiferum as a reducing and capping agent. The formation of PdNPs was optimized at various temperatures i.e. (30°C, 60°C and 90°C) and different leaves extract (5mL and 10mL) in order to control their size and shape. The results indicated that PdNPs synthesized at 10mL leaf extract concentration and 60°C temperature have small sized (5nm) and spherical shape. The nanoparticles formation, their dispersion, size and shape were confirmed by various characterization techniques i.e. UV–Vis spectroscopy, Fourier-transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), thermo gravimetric analysis (TGA) and Dynamic light scattering technique (DLS) analysis. The biologically synthesized PdNPs were tested for size dependent photo degradation of methylene blue and inactivation of bacteria. The PdNPs synthesized at optimized condition (10mL extract concentration and 60°C) have strong photo catalytic activity and reduced 90% methylene blue in 70min. The optimized PdNPs also showed strong bacterial inhibition against Staphylococcus aureus 29(±0.8mm), Bacillus subtilis 19(±0.6mm) and pseudomonas aeruginosa 11(±0.6mm). The results of this examination demonstrate effective applications of extremely active PdNPs.

Photocatalytic reduction of organic pollutant under visible light by green route synthesized gold nanoparticles

We report a rapid method of green chemistry approach for synthesis of gold nanoparticles (AuNPs) using Lagerstroemia speciosa leaf extract (LSE). L. speciosa plant extract is known for its effective treatment of diabetes and kidney related problems. The green synthesis of AuNPs was complete within 30min at 25°C. The same could also be achieved within 2min at a higher reaction temperature (80°C). Both UV–visible spectroscopy and transmission electron microscopy results suggest that the morphology and size distribution of AuNPs are dependent on the pH of gold solution, gold concentration, volume of LSE, and reaction time and temperature. Comparison between Fourier transform infrared spectroscopy (FT-IR) spectra of LSE and the synthesized AuNPs indicate an active role of polyphenolic functional groups (from gallotannins, lagerstroemin, and corosolic acid) in the green synthesis and capping of AuNPs. The green route synthesized AuNPs show strong photocatalytic activity in the reduction of dyes viz., methylene blue, methyl orange, bromophenol blue and bromocresol green, and 4-nitrophenol under visible light in the presence of NaBH4. The non-toxic and cost effective LSE mediated AuNPs synthesis proposed in this study is extremely rapid compared to the other reported methods that require hours to days for complete synthesis of AuNPs using various plant extracts. Strong and stable photocatalytic behavior makes AuNPs attractive in environmental applications, particularly in the reduction of organic pollutants in wastewater.

N-doping Ta2O5 nanoflowers with strong adsorption and visible light photocatalytic activity for efficient removal of methylene blue

Abstract Novel 3D N-doping Ta2O5 nanoflowers (NFs) photocatalysts were synthesized at different annealing temperatures ranging from 700 °C to 850 °C. The microstructure, phase composition, and chemical states of those photocatalysts were characterized in details. The adsorption kinetics as well as photocatalytic performance under visible light irradiation were also investigated. Importantly, compared to N-doping Ta2O5 NFs samples obtained at other nitriding temperatures, the Ta2O5 NFs nitrided at 750 °C displayed high surface adsorption and photocatalytic degradation activity of Methylene Blue (MB) due to the synergistic effect of large surface area, strong surface adsorption, light absorption and photosensitization. The experiment results confirmed that the adsorption of MB to these samples and photocatalytic degradation follow the pseudo-second order chemisorption mechanism and pseudo first order degradation kinetics, respectively. The main reactive species were identified through the scavenging reaction following the order of h+ > OH > O2−. Additionally, degradation product analysis was conducted using liquid chromatography tandem mass spectrometry (LC–MS) technique combined with the UV–vis absorption spectrum. The results showed that the degradation was initiated by demethylation of the dye molecule. The current work may contribute to additional applications of these 3D N-doping Ta2O5 hierarchical nanostructures such as photoelectric chemical (PEC) water splitting, surface adsorption, supercapacitors, solar cells, etc.