Superior Photocatalytic Research Articles

A Study of Superior Photocatalytic Properties of Synthesized TiN through a Facile Approach

A Study of Superior Photocatalytic Properties of Synthesized TiN through a Facile Approach

Eu2+ and Eu3+ Doubly Doped ZnWO₄ Nanoplates with Superior Photocatalytic Performance for Dye Degradation.

Eu2+ and Eu3+ doubly doped ZnWO4 nanoplates with highly exposed {100} facets were synthesized via a facile hydrothermal route in the presence of surfactant cetyltrimethyl ammonium bromide. These ZnWO4 nanoplates were characterized using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectrometry, diffuse UV-vis reflectance spectroscopy, photoluminescence spectrophotometry, and photoluminescence lifetime spectroscopy to determine their morphological, structural, chemical, and optical characteristics. It is found that Eu-doped ZnWO4 nanoplates exhibit superior photo-oxidative capability to completely mineralize the methyl orange into CO2 and H2O, whereas undoped ZnWO4 nanoparticles can only cleave the organic molecules into fragments. The superior photocatalytic performance of Eu-doped ZnWO4 nanoplates can be attributed to the cooperative effects of crystal facet engineering and defect engineering. This is a valuable report on crystal facet engineering in combination with defect engineering for the development of highly efficient photocatalysts.

Superior Photocatalytic Performance of CeO₂ Nanoparticles and Reduced Graphene Oxide Nanocomposite Prepared by Low Cost Co-Precipitation Method.

In this article, cerium oxide nanoparticles (CeO2 NPs) and reduced graphene oxide nanocomposite have been fabricated through simple, easy and cost effective co-precipitation method. The structural, optical and morphological characterization provides the evidence of successful synthesis of CeO2 NPs and nanocomposite. X-ray photoelectron spectroscopic characterization provides useful information about the concentrations and proportions of Ce3+ and Ce4+ ions in nanoparticles as well as in nanocomposite. These studies provide an insight to understand enhanced photocatalytic activity of nanocomposite. The nanocomposite produces 81% photocatalytic degradation of methyl orange compared to only 45% degradation by CeO2 NPs alone.

Boron-Doped Graphene/ZnO Nanoflower Heterojunction Composite with Superior Photocatalytic Activity

The boron-doped graphene (BG) is synthesized successfully by one pot reduce-doping of graphene oxide (GO) with borane tetrahydrofuran (BH3·THF) and the novel BG/ZnO p–n heterojunction composite between p-type BG and n-type ZnO is obtained via a simple hydrothermal method. The samples are characterized by scanning electron microscopy, the Raman spectroscopy and the UV–Vis diffuse spectroscopy. The results confirm the formation of p–n junction between BG and ZnO. The photodegradation of MB demonstrate that the BG/ZnO composite has superior photocatalytic activity under UV–Vis or visible irradiation. The photocatalytic activity k value of BG/ZnO p–n heterojunction composite is 3.1 and 4.5 times as that of r-GO/ZnO and pure ZnO under white light and is 1.8 and 3.9 times under visible light, respectively. The superior photocatalytic activity of the BG/ZnO composite is ascribed to the formation of p–n heterojunction. The p–n heterojunction can promote the separation of electron/hole pairs and inhibit the recombination of electrons in conduction band and holes in valence band by transferring holes from the valence band of n-type ZnO to the valence band of p-type BG.

Construction of Bi 2 O 3 /g-C 3 N 4 composite photocatalyst and its enhanced visible light photocatalytic performance and mechanism

Abstract To improve the photocatalytic (PC) performance of g-C3N4 nano-material, a novel Z-scheme Bi2O3/g-C3N4 composite photocatalyst was synthesized by heat treatment method. Subsequently, the morphologies, chemical structures, optical and photoelectrochemical (PECH) properties of as-obtained photocatalysts were investigated through X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET) surface areas, UV–visible diffuse reflectance spectroscopy (UV–vis DRS), transient photocurrent density, Mott-Schottky (M-S) and electrochemical impedance spectroscopy (EIS) measurement. Furthermore, the PC efficiency was evaluated by degradation of amido black 10B dye. All results indicated that as-fabricated Bi2O3/g-C3N4 photocatalytic system displayed superior PC performance under visible light illumination, which was mainly ascribed to the intense visible light absorbance and the migration of photo-generated carriers adopted a Z-scheme mechanism. Moreover, the degradation of amido black 10B for 3 wt.%Bi2O3/g-C3N4 were about 1.41 and 1.42 times than that of pure g-C3N4 and pure Bi2O3, respectively.

Ultrathin 2D Zirconium Metal-Organic Framework Nanosheets: Preparation and Application in Photocatalysis.

Synthesizing ultrathin 2D metal-organic framework nanosheets in high yields has received increasing research interest but remains a great challenge. In this work, ultrathin zirconium-porphyrinic metal-organic framework (MOF) nanosheets with thickness down to ≈1.5 nm are synthesized through a pseudoassembly-disassembly strategy. Owing to the their unique properties originating from their ultrathin thickness and highly exposed active sites, the as-prepared ultrathin nanosheets exhibit far superior photocatalysis performance compared to the corresponding bulk MOF. This work highlights new opportunities in designing ultrathin MOF nanosheets and paves the way to expand the potential applications of MOFs.

Designing Novel Nonsymmetric Ag/AgI Nanoplates for Superior Photocatalytic Activity.

Precisely engineering the decoration of metal nanoparticles on the special surface of semiconductor represents a promising strategy to design efficient metal-semiconductor heterostructured photocatalysts. This study demonstrates a versatile soft-template method to fabricate a novel nonsymmetrical heterostructured Ag/AgI nanoplate, in which only one side surface of the nanoplate is covered with uniform 2D Ag nanoweb. Compared with symmetrical heterostructure, the nonsymmetrical heterostructure may further facilitate the separation of photogenerated electron-hole pairs and shows a greatly enhanced photocatalytic activity. This study may open up a new way to improve the photocatalytic property by synthesizing nonsymmetrical metal-semiconductor composites.

Ultrasound assisted fabrication of AgBr/TiO2 nano-tube arrays photoelectrode and its enhanced visible photocatalytic performance and mechanism for detoxification of 4-chlorphenol

Abstract In the present work, narrow band gap AgBr nano-particle decorated TiO2 nanotubes arrays (AgBr/TiO2 NTAs) photoelectrode was successfully fabricated through anodization, followed by ultrasonic assisted precipitation process. Subsequently, morphologies and chemical structures were investigated through scanning electron microscope (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). In addition, the optical and photoelectrochemical (PECH) properties were recorded through Ultraviolet–visible diffuse reflectance spectroscopy (UV–vis DRS), transient photocurrent density and Mott-Schottky measurements. Furthermore, the photocatalytic (PC) efficiency was evaluated through the yield of hydroxyl ( OH) radicals and degradation of 4-CP under visible light illumination. All results indicated that as-fabricated AgBr/TiO2 NTAs photoelectrode displayed superior PC performance, which was mainly ascribed to the intense visible light absorbance and high charge separation efficiency. Moreover, the intermediates and toxification change during PC degradation of 4-CP were elucidated according to the UPLC-MS/MS measurement and luminescent bacterial tests.

Photocatalysis: Effective Prevention of Charge Trapping in Graphitic Carbon Nitride with Nanosized Red Phosphorus Modification for Superior Photo(electro)catalysis (Adv. Funct. Mater. 46/2017)

Photocatalysis: Effective Prevention of Charge Trapping in Graphitic Carbon Nitride with Nanosized Red Phosphorus Modification for Superior Photo(electro)catalysis (Adv. Funct. Mater. 46/2017)

Effective Prevention of Charge Trapping in Graphitic Carbon Nitride with Nanosized Red Phosphorus Modification for Superior Photo(electro)catalysis

AbstractThe high occurrence of trapped unreactive charges due to chemical defects seriously affects the performance of g‐C3N4 in photocatalytic applications. This problem can be overcome by introducing ultrasmall red phosphorus (red P) crystals on g‐C3N4 sheets. The elemental red P atoms reduce the number of defects in the g‐C3N4 structure by forming new chemical bonds for much more effective charge separation. The product shows significantly enhanced photocatalytic activity toward hydrogen production. To the best of our knowledge, the hydrogen evolution rate obtained on this hybrid should be the highest among all P‐containing g‐C3N4 photocatalysts reported so far. The trapping and detrapping processes in this red P/g‐C3N4 system are thoroughly revealed by using time‐resolved transient absorption spectroscopy.

Template-free synthesis of mesoporous α-Fe2O3 nanoflowers with short charge-carrier diffuse distance for superior photocatalysis

In this work, well-shaped monodisperse mesoporous α-Fe2O3 nanoflowers were prepared by a facile template-free solvothermal route. The α-Fe2O3 nanoflowers with size of ~80 nm composed of nanobranches with width of ~10 nm. Contributed by the short charge-carrier diffuse distance of thin branches, the as-prepared mesoporous α-Fe2O3 nanoflowers possess notably higher phtotocatalytic activity in comparison with non-porous samples, commercial α-Fe2O3 and TiO2 by a model organic dye degradation reaction of Rhodamine B. The kinetic constant of mesoporous α-Fe2O3 nanoflowers for Rhodamine B degradation is about twice that of the non-porous materials and 10 times that of commercial α-Fe2O3 photocatalyst. Therefore, a simple method is developed to access the highly active mesoporous α-Fe2O3 nanoflowers, and the as-prepared material is potential to be used in photocatalysis or solar energy harvest.

Highly ordered Fe3+/TiO2 nanotube arrays for efficient photocataltyic degradation of nitrobenzene

Highly ordered TiO2 nanotube arrays (TiO2 NTs) were prepared through a facile two-step electrochemical anodization, subsequently, active iron ions were introduced into the TiO2 NTs via a direct impregnation method. The XPS results showed that the iron elements existed in TiO2 NTs in the form of Fe3+ ions. Compared with the undoped TiO2 NTs, the absorption edge of Fe3+/TiO2 NTs showed an overt red shift and the photocurrent improved obviously, which indicated that Fe3+/TiO2 had a much higher photocatalytic activity. The optimal doping content was tested to be 0.1mol/L which could make the photocatalytic activity of TiO2 NTs obviously improves under both visible and ultraviolent light. The prepared samples were adopted as photocatalyst to degrade nitrobenzene (NB). The reaction rate constants ks under UV light were in the order kone-stepTiO2NTs=0.00338<ktwo-steTiONTs=0.00455<kFe3+/TiONTs=0.00736 which showed the superior photocatalysis activity of Fe3+/TiO2 NTs. The final degradation products were probed to be CO2 and H2O, which demonstrated that NB could be completely mineralized to harmless inorganic substance. The mechanism of NB degradation with Fe3+/TiO2 was also discussed and the quenching experiments further confirm that OH, h+ and O2− are active intermediates in the process of photocatalytic degradation.

Synergetic photo-epoxidation of propylene with molecular oxygen over bimetallic Au–Ag/TS-1 photocatalysts

Au–Ag bimetallic nanoparticle-supported microporous titanium silicalite-1 catalysts were prepared via a hydrothermal-immersion method, and their structures were examined. These materials serve as efficient catalysts for the photosynthesis of propylene oxide via the epoxidation of propene. The Au/Ag mass ratio and reaction temperature were demonstrated to have significant effects on the catalytic activity and selectivity of propylene oxide. The optimal formation rate (68.3 μmol/g·h) and selectivity (52.3%) toward propylene oxide were achieved with an Au:Ag mass ratio of 4:1. Notably, the strong synergistic effect between Au and Ag resulted in superior photocatalysis of the bimetallic systems compared with those of the individual systems. A probable reaction mechanism was proposed based on the theoretical and experimental results.

Salt-assisted Synthesis of Hollow Bi2WO6 Microspheres with Superior Photocatalytic Activity for NO Removal

Hollow Bi2WO6 microspheres are successfully synthesized by a facile ultrasonic spray pyrolysis (USP) method using NaCl as a salt template. The as-prepared hollow microspheres assembled as nanoplates with dimensions of approximately 41–148 nm and are dispersed with non-uniform pores on the template surface. By swapping the salt template with KCl or Na2SO4, different morphologies of Bi2WO6 are obtained. The experimental results demonstrate that NaCl plays a key role on the formation of Bi2WO6 with hollow structures. The specific growth mechanism of hollow microspheres was studied in detail. The Bi2WO6 hollow microspheres exhibit an excellent photocatalytic efficiency for NO removal under solar light irradiation, which is 1.73 times higher than for the Bi2WO6 obtained in the absence of any salt template. This enhancement can be ascribed to the simultaneous improvement on the surface area and visible light-harvesting ability from the hollow structures. Electron spin resonance (ESR) results suggest that both radicals of •OH and •O2− are involved in the photocatalytic process over the BWO-NaCl sample. The production of •O2− radicals offers better durability for NO removal.

Thylakoid-Inspired Multishell g-C3N4 Nanocapsules with Enhanced Visible-Light Harvesting and Electron Transfer Properties for High-Efficiency Photocatalysis.

Inspired by the orderly stacked nanostructure and highly integrated function of thylakoids in a natural photosynthesis system, multishell g-C3N4 (MSCN) nanocapsule photocatalysts have been prepared by SiO2 hard template with different shell layers. The resultant triple-shell g-C3N4 (TSCN) nanocapsules display superior photocatalysis performance to single-shell and double-shell counterparts owing to excellent visible-light harvesting and electron transfer properties. Specially, with the increase of the shell layer number, light harvesting is greatly enhanced. There is an increase of the entire visible range absorption arising from the multiple scattering and reflection of the incident light within multishell nanoarchitectures as well as the light transmission within the porous thin shells, and an increase of absorption edge arising from the decreased quantum size effect. The electron transfer is greatly accelerated by the mesopores in the thin shells as nanoconduits and the high specific surface area of TSCN (310.7 m2 g-1). With the tailored hierarchical nanostructure features, TSCN exhibits a superior visible-light H2-generation activity of 630 μmol h-1 g-1 (λ > 420 nm), which is among one of the most efficient metal-free g-C3N4 photocatalysts. This study demonstrates a bioinspired approach to the rational design of high-performance nanostructured visible-light photocatalysts.

Fabrication of Ag 2 O/TiO 2 -Zeolite composite and its enhanced solar light photocatalytic performance and mechanism for degradation of norfloxacin

Abstract Norfloxacin, as an antimicrobial drug, has frequently been detected in municipal plants, which is predicted to be potential risk on human beings and the environment. In the present study, zeolite immobilizes silver oxide decorated titanium dioxide (Ag2O/TiO2-Zeolite) composite has been fabricated through modified sol-gel method. Afterwards, physicochemical properties of the as-fabricated Ag2O/TiO2-Zeolite sample are systematically studied by scanning electron microscope, X-ray diffraction, X-ray photoelectron microscopy, ultraviolet visible diffuse reflectance spectroscopy and surface photovoltage spectra measurements. Besides these, photocatalytic (PC) performance of Ag2O/TiO2-Zeolite composite is evaluated by photodecomposition of norfloxacin under simulated solar light illumination and generation of active hydroxyl ( OH) radicals. Results indicate that the decorated Ag species exists in the form of Ag2O, which can greatly enhance the visible light absorbance and charge separation efficiency. Furthermore, Ag2O/TiO2-Zeolite composite displays superior PC performance, which is mainly ascribed to the intense light absorbance in visible region, narrow band gap level and high charge separation efficiency. In addition, the solar light PC degradation pathways of norfloxacin are proposed according to the HPLC-MS/MS measurements, including hydroxylation addition to parent compound, decarboxylation and defluorination of side chain from the norfloxacin. Moreover, the as-fabricated Ag2O/TiO2-Zeolite composite exhibits high stability after consecutive utilization for seven times.

A Heterojunction Design of Single Layer Hole Tunneling ZnO Passivation Wrapping around TiO2Nanowires for Superior Photocatalytic Performance.

Nanostructured hybrid heterojunctions have been studied widely for photocatalytic applications due to their superior optical and structural properties. In this work, the impact of angstrom thick atomic layer deposited (ALD) ZnO shell layer on photocatalytic activity (PCA) of hydrothermal grown single crystalline TiO2 nanowires (NWs) is systematically explored. We showed that a single cycle of ALD ZnO layer wrapped around TiO2 NWs, considerably boosts the PCA of the heterostructure. Subsequent cycles, however, gradually hinder the photocatalytic activity (PCA) of the TiO2 NWs. Various structural, optical, and transient characterizations are employed to scrutinize this unprecedented change. We show that a single atomic layer of ZnO shell not only increases light harvesting capability of the heterostructure via extension of the absorption toward visible wavelengths, but also mitigates recombination probability of carriers through reduction of surface defects density and introduction of proper charge separation along the core-shell interface. Furthermore, the ultrathin ZnO shell layer allows a strong contribution of the core (TiO2) valence band holes through tunneling across the ultrathin interface. All mechanisms responsible for this enhanced PCA of heterostructure are elucidated and corresponding models are proposed.

Lanthanum ions-induced synthesis of ZnO nanostructures from zinc foil: Morphology change and photocatalytic activity

High-density aligned ZnO nanorod array film was synthesised by hydrothermal oxidation of zinc foil in a mixture including n-butylamine and lanthanum nitrate aqueous solution. The shape of ZnO nanostructure was strongly associated with the amount of lanthanum ions, which provided a valuable way to control the rate of nucleation and growth of ZnO. HRTEM, XRD and XPS analysis confirmed that the La3+ had been doped into ZnO lattice, which led to the red shift of the absorption edges and the decrease of PL intensity. The photocatalytic studies showed that the ZnO nanorod array film exhibited superior photocatalysis for the degradation of both methyl orange and methylene blue solutions due to its exposed crystal plane, density and the defects on the surface.

English

English

Carbon Dots Sensitized BiOI with Dominant {001} Facets for Superior Photocatalytic Performance

Degrading and removing harmful compounds by the use of semiconductor photocatalysts has been testified to be and effective and attractive green technique in wastewater treatment. Herein, carbon dots sensitized BiOI with highly exposed {001} facets has been prepared and used to study the photocatalytic degradation of methyl orange (MO). Due to the improved charge separation, transfer, and optical absorption, the photocatalytic performance for methyl orange degradation of the carbon dots/{001} BiOI nanosheets is 4 times higher than that of the {001} BiOI nanosheets under visible light irradiation. Additionally, the carbon dots/{001} BiOI nanosheets also have superior stability after 5 cyclings.