Visible Light Responsive Photocatalytic Activity Research Articles

Improved visible light response photocatalytic activity of CuWO4/g-C3N4 nanocomposites for degradation of organic dyes

Improved visible light response photocatalytic activity of CuWO4/g-C3N4 nanocomposites for degradation of organic dyes

Facile fabrication of novel In2S3–BiOCl nanocomposite-supported porous polymer monolith as new generation visible-light-responsive photocatalyst for decontaminating persistent toxic pollutants

We report synthesizing a novel p-In2S3 and n-BiOCl heterojunction nanocomposite of varying β-In2S3 stoichiometry (10–50%) fabricated via. The hydrothermal and combustion methods. In2S3–BiOCl nanocomposites were homogeneously integrated onto a porous poly(ethylene glycol dimethacrylate) monolith to serve as a high-performance visible-light-responsive renewable photocatalyst decontaminating toxic organic pollutants such as Rhodamine B. The photocatalyst's structural and surface features were characterized using ppowder X-ray diffraction, X-ray photoelectron spectrometer, high-resolution transmission electron microscopy–selected area electron diffraction, field-emission scanning electron microscopy-energy-dispersive X-ray spectral, UV–Vis-diffuse reflectance spectral, photoluminescence spectral, Fourier transforms infrared, electrochemical impedance spectroscopy, and Brunauer–Emmett–Teller/Barrett-Joyner-Halenda (BJH) analysis. Using 20 wt% of In2S3 composition in the In2S3–BiOCl nanocomposite facilitated better electron–hole pair separation with excellent visible light responsive photocatalytic activity, confirmed through electrochemical impedance spectroscopy, photoluminescence spectral and bandgap measurements. The Brunauer–Emmett–Teller/BJH analysis revealed that the In2S3–BiOCl nanocomposite-loaded poly(ethylene glycol dimethacrylate) monolith had high surface area and pore dimensions, with voluminous photoactive sites. The role of analytical parameters such as pH, nanocomposite ratio, photocatalyst dosage, dye concentration, photosensitizers/oxidizers, and light intensity were studied/optimized. Under the optimized conditions of pH 2.0, 100 mg photocatalyst dosage, 30 ppm dye concentration, 1.0 mM KBrO3, and 300 W/cm2 visible light intensity, the monolithic photocatalyst showed a dissipation efficiency of ≥98.6% for Rhodamine B in ≤0.3 h. The renewable photocatalyst can be reused for six cycles without loss in efficiency/performance and proved promising in efficiently decontaminating persistent organic pollutants at an affordable cost and time.

Investigating the Effect of Bi2MoO6/g-C3N4 Ratio on Photocatalytic Degradation of Sulfadiazine under Visible Light

In this study, a series of Bi2MoO6/g-C3N4 composites were prepared through a wet-impregnation method, and their photocatalytic properties were investigated for the degradation of sulfadiazine (SDZ) under visible light irradiation. Physical and chemical characterizations were carried out using X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), photoluminescence spectroscopy (PL), UV-vis diffuse reflectance spectra (UV-vis), and electrochemical impedance spectra (EIS). Compared to pure g-C3N4, the introduction of Bi2MoO6 significantly enhanced the visible light responsive photocatalytic activity, with the 1:32 Bi2MoO6/g-C3N4 composite exhibiting the highest photodegradation efficiency towards SDZ under visible light irradiation with a photocatalytic efficiency of 93.88% after 120 min of visible light irradiation. The improved photocatalytic activity can be attributed to the formation of a heterojunction between Bi2MoO6 and g-C3N4, which promotes the transfer of photogenerated electron-hole pairs, thereby elevating its photocatalytic activity. The results suggest that Bi2MoO6/g-C3N4 composites have potential application for the degradation of sulfonamides in aquatic environments.

Bi Doped TiO2 as a Photocatalyst for Enhanced Photocatalytic Activity

This study is based on the preparation of TiO2 and bismuth doped TiO2 (Bi-TiO2) nanoparticles by surfactant-assisted sol-gel approach. The physiochemical characteristics of prepared samples were examined by X-ray diffraction technique (XRD), Fiel emission scanning electron microscopy-energy dispersive analysis (FESEM-EDS), and UV-visible diffuse reflectance spectroscopy (UV-vis DRS). The XRD patterns revealed that the anatase crystal phase was only formed with high crystallinity. The band gap energies were measured to be of 3.11 eV for TiO2-2 and 3.02 eV for Bi-TiO2 by ultraviolet (UV)-visible diffuse reflectance spectroscopy, revealing that doping Bi improves the efficient interactive relation of the catalyst with visible light. Also, EDS results confirm that Bi particles are immobilized on the surface of TiO2 successfully. The activities of the catalysts were tested by photocatalytic degradation of methylene blue (MB) under the visible light. Bi-TiO2 photocatalyst could achieve the best MB degradation percentage of 70.2% after 180 min. of visible irradiation. Additionally, effect of some experimental parameters such as effect of humic acid (HA) and pH has been evaluated as much as reusability of catalyst. The characterization results confirmed the successful and desired preparation of the catalysts. The Bi-TiO2 presented significant visible light response photocatalytic activity for the degradation of MB.

Polyvinylpyrrolidone assisted-preparation of AgBr with enhanced visible light responsive photocatalytic activity

• AgBr was prepared by a hydrothermal method with PVP. • Separation of photoactivated carriers has been largely promoted. • The level of •O 2 - was greatly boosted. • PVP-AgBr possess superior photocatalytic activity. In this paper, AgBr photocatalyst was prepared by a precipitation method using silver nitrate and potassium bromide as raw materials. The effects of polyvinylpyrrolidone (PVP) on the preparation and photocatalytic property of AgBr were investigated. The samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), surface photovoltage (SPS), ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS) and specific surface area (BET). Using rhodamine B as a model pollutant, photocatalytic performance of the photocatalyst prepared was tested under visible light irradiation. The results indicate that AgBr prepared by adding of PVP has superior photocatalytic activity. Under visible light irradiation, the destruction rate constant of rhodamine B (RhB) on PVP-AgBr is 4.79 times of that on the reference AgBr.

Homogeneous double-layer TiO2-ZrO2-SiO2 photocatalyst with multi-heterojunction structure for enhanced visible light-responsive photocatalytic activity

Traditional heterojunctions are usually constructed with different material systems, resulting in weaker interfacial effects in the catalytic system. In order to solve this problem, we use a simple sol–gel method to construct a homogeneous double-layer TiO2-ZrO2-SiO2 photocatalyst with multi-heterojunction (d-TZS), which can effectively improve the photocatalytic property. By investigating the influence of various factors on the photocatalytic performance, the degradation rate of Rh B by d-TZS can reach about 99.6 % within 40 min of photoreaction, and Rh B almost completely degraded within 60 min. This is attributed to three aspects of homogeneity, multiple heterojunctions and oxygen vacancies. Firstly, the inner and outer layers are homogeneous with excellent compatibility, and the outer layer has strong adsorption. Secondly, the multi-heterostructure which forms between the inner-layer multi-heterojunction and the outer layer can separate the photogenerated electrons in each layer to a certain extent. Finally, the oxygen vacancies formed after the bonding of the outer and inner layers can further enhance the mobility of photogenerated carriers. This idea provides new methods for the study of homogenous multiple heterojunctions with high visible light degradation rate.

A facile hydrothermal synthesis of few-layer oxygen-doped g-C3N4 with enhanced visible light-responsive photocatalytic activity

Abstract Graphitic carbon nitride (g-C3N4) has aroused extensive attention as a promising candidate for metal-free photocatalysts but is oppressed by its limited photocatalytic efficiency because of the rapid recombination of photogenerated carriers, finite actual reactive sites and poor optical absorption. Doping modification as well as constructing two-dimensional layered structure of g-C3N4 are widely used as effective strategies to improve photocatalytic performance. However, the present synthesis methods still need to improve. In this work, we report a facile hydrogen peroxide assisted hydrothermal approach to synthesize layered oxygen-doped g-C3N4 for photocatalytic degradation of RhB. The obtained samples were investigated in detail by a series of characterization methods. Compared with bulk g-C3N4, the as-prepared few-layer oxygen-doped g-C3N4 sample has modulated CB and VB potentials, lower band gap energy, larger specific surface area, and higher separation efficiency of charge carriers. The photocatalytic RhB degradation constant over few-layer oxygen-doped g-C3N4 is approximately 5-fold higher than that of bulk g-C3N4 counterpart. Finally, an enhanced photocatalytic RhB degradation mechanism was proposed.

A phase separation in a protonated layered nickel titanate to form Ni-doped anatase/rutile TiO2 nanocomposite with efficient visible-light responsive photocatalytic activity

ABSTRACT We report a simple methodology for the preparation of an efficient visible-light responsive TiO2 photocatalyst through acid treatment of a lepidocrocite-type layered nickel cesium titanate (Cs0.7Ti1.65Ni0.35O4) for interlayer protonation and subsequent calcination at different temperatures (400–600°C) to induce structural transformation. The Ni-doped anatase/rutile nanocomposite possessing a morphology similar to that of protonated layered nickel titanate is obtained at all calcination temperatures. The sample obtained at 600°C exhibits the highest visible-light responsive photocatalytic activity for decomposition of the aqueous methylene blue dye under visible-light (λ > 420 nm) irradiation. The activity is 14 times higher than that of P25 (standard TiO2 photocatalyst) modified with Ni2+ and 3 times higher than that of NiTiO3 (visible-light responsive photocatalyst). The efficient visible-light responsive photocatalytic activity is ascribable to the visible-light absorption ability of the TiO2 phase owing to Ni-doping. Also, an efficient electron transfer across anatase–rutile interfaces for inhibition of charge recombination could be responsible for the activity. This methodology is a new route for efficient visible-light responsive photocatalysts based on TiO2 doped with various elemental species. This is because lepidocrocite-type layered titanates are available in a variety of chemical compositions.

Influences of silver halides AgX (X = Cl, Br, and I) on magnesium bismuth oxide photocatalyst in methylene blue degradation under visible light irradiation

AgX/MgBi2O6 composites (X = Cl, Br, and I), prepared from the hydrothermal procedure combined with a co-precipitation method, display unique visible light responsive photocatalytic activity. The catalytic performance of the AgX/MgBi2O6 composites were evaluated through the photodegradation of methylene blue (MB, 15 ppm) under white-light light-emitting diode irradiation (2.5 W, power density: 0.38 Wcm−2). Among the AgX/MgBi2O6 composites, the AgI/MgBi2O6 composite, with molar ratio of AgI to MgBi2O6 as 3:1, exhibited the highest photocatalytic performance within 20 min (degradation efficiency: 99.5 %) while MgBi2O6, AgCl/MgBi2O6, and AgBr/MgBi2O6 composites achieved degradation efficiency of 14.9 %, 24.9 % and 56.1 % respectively. The main reason of superior photocatalytic activity in AgI/MgBi2O6 composite attributes to the pn junction between AgI nanoparticles and MgBi2O6 effectively enhancing the charge separation efficiency and reducing the recombination rate of electron–hole pairs. This study revealed that hydroxyl and oxygen radicals are the major species involved in the degradation of MB from the photoactivated AgI/MgBi2O6 composite. To develop a practical application of this new material, the samples of AgI/MgBi2O6 composite have demonstrated excellent photocatalytic performance in degradation of various dyestuffs (92.3 %–99.5 % degradation within 10 min) under visible light irradiation and 99.8 % MB degradation under sunlight irradiation within 6 min.

Enhanced hardness and photocatalytic performance in anodic N-doped TiO2 layer on titanium using a non-aqueous nitrate electrolyte

An N-doped TiO2 layer with enhanced hardness and photocatalytic performance was fabricated on a titanium (Ti) substrate through anodization in a non-aqueous electrolyte comprising nitrate and glycerol, followed by heating at 723 K in air. Glycerol as an electrolyte solvent formed a homogeneous and dense oxide layer and resulted in improved layer hardness. The fabricated layer comprised rutile and anatase TiO2 with ~1 at% of nitrogen doping. Visible-light responsive photocatalytic activity was enhanced with increasing nitrate concentration in the electrolyte, as this optimized the anatase/rutile TiO2 ratio of the layer. The fabricated TiO2 layer showed excellent antibacterial activity that was superior to a commercially available photocatalytic TiO2 layer, demonstrating that the proposed treatment process is capable of fabricating surface modified Ti biomaterial.

Synthesis of LaFeO3/Bi3NbO7 p-n heterojunction photocatalysts with enhanced visible-light-responsive activity for photocatalytic reduction of Cr(Ⅵ)

LaFeO3/Bi3NbO7 p-n heterojunction photocatalysts were prepared successfully through an in-situ growth method. The phase structure, optical property, morphology and microstructures of the obtained samples were studied by X-Ray diffractometer (XRD), Ultraviolet–visible absorption spectrum (UV–vis DRS), photoluminescence (PL) spectroscopy, transmission electron microscope (TEM), high resolution transmission electron microscope (HRTEM) and scanning electron microscope (SEM). The visible light responsive photocatalytic activity of as-obtained samples were investigated by the photo-reduction of Cr (Ⅵ). The effects of preparation conditions (proportion of BNO/LFO and temperature) on the activity were studied. Results showed that the as-obtained BNO-LFO-200-5 composite behaved the best photocatalytic activity (with rate constant of 0.0212 min−1) among all the obtained samples. The rate constant was about 42.4-times and 17.7-times as that of pristine BNO (0.0005 min−1) and LFO (0.0012 min−1), respectively. The enhanced photocatalytic property of the as-prepare LaFeO3/Bi3NbO7 composites can be ascribed to the formation of p-n junction between BNO and LFO, which significantly increased the separation efficiency of photo-excited electron-holes.

Enhanced visible-light responsive photocatalytic activity of Bi25FeO40/Bi2Fe4O9 composites and mechanism investigation

Pure Bi25FeO40, Bi2Fe4O9, and different weight ratios of Bi25FeO40/Bi2Fe4O9 composite photocatalysts have been synthesized via a hydrothermal process combined with a mixing-calcination method and evaluated as visible-light responsive catalyst for the degradation of Rhodamine B (RhB). All the as-prepared samples have been characterized by a range of techniques including X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), UV–vis absorption spectra (DSR), Field Emission Scanning Electron Microscope (FE-SEM), Transmission electron microscope (TEM) and High-resolution TEM (HRTEM). The XRD, FT-IR, TEM and HRTEM results confirm that the composite only consists of Bi25FeO40 and Bi2Fe4O9. In the Bi25FeO40/Bi2Fe4O9 composites, closely contacted interfaces have been observed. Compared with the single-phase Bi25FeO40 and Bi2Fe4O9, Bi25FeO40/Bi2Fe4O9 composites exhibit enhanced visible-light responsive photocatalytic activities. The photocatalytic efficiency of optimized Bi25FeO40/Bi2Fe4O9 composite with Bi2Fe4O9 weight ratio of 30% is about 8.8 and 6.2 times higher than that of pure Bi25FeO40 and Bi2Fe4O9, respectively. On the basis of electronic energy-band structure analysis, the active species trapping experiments and the electrochemical impedance spectrum (EIS) performance, a heterojunction-type charge transfer mechanism interpreting the enhanced photocatalytic activities of the composite are proposed and discussed. In addition, the effects of different Bi25FeO40/Bi2Fe4O9 weight ratios and their geometry architecture on photocatalytic activities are also thoroughly discussed.

Preparation of novel Ag2O/Na3Bi(PO4)2 heterogeneous nanostructures with enhanced visible-light responsive photocatalytic activity

Novel Na3Bi(PO4)2 nanostructures were synthesized for the first time by a facile hydrothermal reaction. Ag2O nanoparticles were deposited on the surface of Na3Bi(PO4)2 nanostructures by the chemical precipitation method. The photocatalytic performance of the pure Ag2O nanoparticles, Na3Bi(PO4)2 nanostructures and Ag2O/Na3Bi(PO4)2 heterogeneous nanostructures were evaluated by photocatalytic decolorization of Rhodamine B (RhB) solution under visible-light irradiation. Compared with the pure Na3Bi(PO4)2 nanostructures, the Ag2O/Na3Bi(PO4)2 heterogeneous nanostructures exhibited an obviously enhanced photocatalytic activity. And the photocatalytic stability of the Ag2O/Na3Bi(PO4)2 heterogeneous nanostructures is much higher than that of the Ag2O nanoparticles.

Modification strategies for enhancing the visible light responsive photocatalytic activity of the BiPO4nano-based composite photocatalysts

The present issues related to environmental purification have led to a great need for the development of a superior oxidation process to solve the life-threatening problem. The use of the BiPO4nanomaterial in photocatalysis is one of the best methods for the treatment of wastewater due to its less harmful nature.

Visible Light-Responsive Photocatalytic Activity of Boron Nitride Incorporated Composites.

Photocatalysts are essential to promote the highly efficient applications of solar energy in water splitting and/or the degradation of organic contaminations. Especially, the visible light-responsive photocatalysts could benefit with the cost-effective splitting or degradation due to the unlimited sunlight and the absence of expensive light emitter. In the photocatalysts, the charge transfer rates as well as the hole-electron recombination rate are two critical factors that determine the photocatalytic activity, which could also be affected by the dimension, defects, doping and morphologies controlled by the synthesis methods. Boron nitride (BN) is an ultrawide-bandgap semiconductor, and the combination of BN with the visible light-responsive photocatalysts has been found to be effective in enhancing the photocatalytic activities. Therefore, it should be meaningful to understand the BN incorporated photocatalytic composites in depth, including the synthetic approaches, the activity improving mechanisms and the versatile applications. In this review, we mainly focused on the assembly method of BN incorporated photocatalysts; the activity enhancing mechanism by introducing the BN in the photocatalytic composites as well as the properties and the applications. In the end, we gave a conclusion and an outlook for the BN incorporated photocatalytic composites.

Bi2O2(OH)NO3/AgI heterojunction with enhanced UV and visible-light responsive photocatalytic activity and mechanism investigation

Fabricating heterojunction between a wide-band-gap semiconductor and a narrow-band-gap semiconductor has become an important strategy to simultaneously improve the photoabsorption and charge separation. In this work, a new heterojunction photocatalyst Bi2O2(OH)NO3/AgI was prepared through a facile in-situ crystallization method under ambient atmosphere. The crystal morphology, surface structure and element distribution were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray (EDX) mapping and X-ray photoelectron spectroscopy (XPS). Compared with the pristine Bi2O2(OH)NO3 and AgI, Bi2O2(OH)NO3/AgI shows much enhanced degradation performance for eliminating MO regardless of UV or visible light. Photocurrent, electrochemical impedance spectra (EIS) and photoluminescence (PL) demonstrated that the enhanced photocatalytic activity is ascribed to the greatly promoted charge separation and transfer resulted from the matchable band energy levels of Bi2O2(OH)NO3 and AgI, favoring the formation of heterojunction. In addition, according to the active species trapping experiment, the main active species are superoxide radicals (O2−) and holes (h+) during the degradation process.

Oxygen vacancies and phosphorus codoped black titania coated carbon nanotube composite photocatalyst with efficient photocatalytic performance for the degradation of acetaminophen under visible light irradiation

In the past two decades, carbon-titania composite photocatalysts had attracted extensive attention for high photocatalytic performance. However, their visible light driven activity was still limited. Therefore, it was urgent to find a way to improve its visible light responsive photocatalytic activity. In the present work, a novel efficient visible light driven photocatalysts, oxygen vacancies and phosphorus (P) codoped titania coated carbon nanotube composites (OVPTCN), were prepared by a facile two step solvothermal and phosphorization method for the first time. The obtained sample exhibited significantly enhanced photocatalytic performance for acetaminophen (ACE) degradation under visible light irradiation. The effects of carbon nanotube (CNT) amount and phosphorization content on the photocatalytic efficiency for ACE degradation were also investigated deeply. Results showed that the optimal sample exhibited a high rate constant of 0.025 min-1 for ACE degradation in contrast to that of pure TiO2 (0.00053 min-1) and titania-carbon nanotube (TCN) composite (0.0036 min-1). The characterization results suggested that phosphorization could produce oxygen vacancies and P dopants in TiO2, thus narrowing the band gap of TiO2, increasing the transfer and separation efficiency of photogenerated charges. Moreover, it was revealed by EIS Nyquist plots that CNT got better conductivity after the solvothermal reaction and phosphorization, which also increased the transfer efficiency of charges. Therefore, the synergistic effect of P doping, oxygen vacancies and better conductivity of CNT resulted in the significantly enhanced visible light responsive photocatalytic performance. The transformation products and degradation pathway were analyzed based on the results of liquid chromatography-mass spectrometry (LC/MS). Our work provided a new way to prepare efficient visible light driven composite photocatalysts for drugs removal.

Theoretical study of the rutile based semiconductor with visible-light responsive photocatalytic activity for water splitting

The cluster expansion formalism combined with the accurate first-principles calculations were performed to investigate the stabilities, the electronic structures and the optical absorption of the rutile based semiconductor TiPt7O16. Our comprehensive calculations have predicted that TiPt7O16 is the most stable structure among the hundreds of the configurations of Pt substituted rutile TiO2 (Ti1-xPtxO2 (R), x = 0–1). More importantly, the accurate HSE06 calculations indicate that TiPt7O16 is a potential visible-light responsible photocatalyst with the band gap of 1.70 eV. In addition, the Pt-terminated (010) and Ti & Pt-terminated (011) surfaces are suitable for catalyzing the overall water splitting, due to their band edges span over the required redox potential.

Preparation and visible light responsive photocatalytic activity of Fe3O4/Ni-Al-Ce LDH/Bi2WO6 composites

Novel Fe3O4/Ni-Al-Ce LDH/Bi2WO6 composites were prepared through a hydrothermal method and co-precipitation method. The morphologies and structures of the photocatalysts were characterized by XRD, Raman, TEM, UV-vis-DRS, BET surface area and VSM techniques. The photocatalytic performances of the photocatalysts were investigated by the decolorization of methyl orange (MO) under visible-light irradiation. The results showed that the Fe3O4/Ni-Al-Ce LDH/Bi2WO6 composites exhibited greater photocatalytic activities compared to pure Bi2WO6 and the Ni-Al-Ce LDH; the decolorization rate of MO was 87% within 60 min under visible-light irradiation. The decolorization efficiency of the composite material remained at 71% after 4 recycling runs, showing improved stability. Furthermore, the experimental results also showed that the photocatalytic reactions for the composites followed first-order reaction kinetics. Therefore, the Fe3O4/Ni-Al-Ce LDH/Bi2WO6 composites were photocatalysts with high efficiencies and stabilities for a photocatalytic reaction of an organic pollutant, and this study provides a new, effective method for the development of wastewater treatment.

Construction of CQDs-Bi20TiO32/PAN electrospun fiber membranes and their photocatalytic activity for isoproturon degradation under visible light

The CQDs-Bi20TiO32 photocatalysts exhibited high visible-light responsive photocatalytic activity. To achieve the cyclic utilization of CQDs-Bi20TiO32, the novel flexible CQDs-Bi20TiO32/PAN fiber membranes were prepared by a simple coaxial electrospinning technique. It was found that the CQDs-Bi20TiO32 photocatalyst could be firmly and uniformly fixed on the surfaces of electrospun fibers and the composite fiber membranes possessed the hierarchical macro- and mesoporous structure. The loaded CQDs-Bi20TiO32 endowed the composite fiber with an obvious photocatalytic activity for the degradation of the herbicide isoproturon under visible light irradiation. Among these samples, S3 at photocatalyst dosage 15w/v% had the highest degradation efficiency for isoproturon. Meanwhile, the core-shell structured inorganic-organic hybrid fiber membranes have a significant advantage in the recyclability for photocatalyts. The flexible CQDs-Bi20TiO32/PAN electrospun fiber membranes would have potential applications in efficient removal of organic contaminants.