Visible Light Photocatalytic Performance For Degradation Research Articles

Hydrothermal synthesis of Bi2WO6/Bi2O4 heterojunction with WO3 and NaBiO3·2 H2O powders as precursors to improve visible light photocatalytic degradation performance

The limited visible light response range and fast recombination rate of photoinduced carriers restrict the photocatalytic performance of Bi2WO6. Herein, a novel low temperature hydrothermal approach was developed to construct the Bi2WO6/Bi2O4 heterojunction with WO3 and NaBiO3•2 H2O powders as precursors and the latter as the only bismuth source. During the hydrothermal reaction, WO3 first reacts with NaBiO3·2 H2O to generate Bi2WO6 and then the residual NaBiO3·2 H2O converts into Bi2O4, in-situ forming the Bi2WO6/Bi2O4 heterojunction with the co-shared Bi atoms. The content of Bi2WO6 in the heterostructure can be facilely modulated by changing the amount of WO3 added. The construction of Bi2WO6/Bi2O4 heterojunction could not only extend the spectral response range but also improve the separation efficiency of photoinduced charges. Consequently, the photocatalytic degradation performance to tetracycline (phenol) for the optimal Bi2WO6/Bi2O4 heterostructure is 5.19 and 1.77 times (4.75 and 1.66 times) higher than that of single Bi2WO6 and Bi2O4 under visible light, respectively. The capture experiments of active species and electron spin resonance spectra demonstrate that radicals (·O2-) and holes (h+) are the first and second important active species, respectively, during the catalytic degradation. Our work provides a new idea for the fabrication of high-performance Bi2WO6-based junction photocatalysts.

Alkali-Assisted Solvothermal Synthesis of I-deficient Nanoplatelet BiOI Microflowers with Enhanced Visible-Light Photocatalytic Performance for Degradation of Organic Pollutants

I-deficient nanoplatelet bismuth oxyiodide (BiOI) microflowers were successfully synthesized via a one-pot solvothermal method using NaOH. Results demonstrated that OH– played a key role in regulating the morphology, pore structure, and energy band structure of the prepared samples. As the volume of NaOH increased, the size of the BiOI microflowers gradually decreased, and the specific surface area and pore volume increased, providing more accessible active sites for photocatalytic reactions. Additionally, some iodine atoms in B-7 (i.e., 7 mL of a 1.0 M NaOH solution was added during the synthesis process) were replaced by hydroxide ions, affording B-7 with slight defects. The loss of iodine atoms shifted the valence band maximum (VBM) from 1.372 eV for the pristine BiOI (B-0) to 1.596 eV for I-deficient BiOI (B-7). The lowered VBM provides more oxidative holes, which is favorable for the oxidation reaction. The photocatalytic activities of the prepared samples were evaluated via the photodegradation of various organic pollutants, such as methyl orange, Rhodamine B, and phenol, under visible light. Owing to the higher surface area and pore volume, lower VBM, and presence of surface defects, B-7 exhibited the highest degradation efficiency among all of the samples.

Facile integration of brown TiO2−x with Bi4V2O11 and BiVO4: Double S-scheme mechanism for exceptional visible-light photocatalytic performance in degradation of pollutants

Heterogeneous photocatalysis has been denoted as a promising approach to dealing with environmental and energy crises. Herein, quantum dots (QDs) of TiO2−x/Bi4V2O11/BiVO4 (TOVBBV) heterojunction photocatalysts were successfully synthesized through a facile one-pot hydrothermal process with varying amounts of integrated Bi4V2O11 and BiVO4 semiconductors. The resultant photocatalysts were characterized by XPS, FT-IR, EDX, XRD, PL, EIS, SEM, TEM, HRTEM, BET, and UV–vis DRS techniques, and their photocatalytic efficiencies were examined via removing tetracycline (TC), azithromycin (AZi), and rhodamine B (RhB) under visible-light illumination. The results showed exceptionally promoted photocatalytic degradation efficiencies of the studied pollutants using the ternary TOVBBV-2 nanocomposite. The TOVBBV-2 nanocomposite was 45.4, 11.6, and 19.8-times more effective than TiO2, 7.24, 5.85 and 2.34-folds better than TiO2−x, and 9.81, 9.23, and 1.61-times more effective than Bi4V2O11/BiVO4 for photooxidation of TC, AZi, and RhB, respectively. The significant enhancement in the photocatalytic efficacy of the TOVBBV-2 nanocomposite originated from the defective oxygen sites in the titanium dioxide structure, which subsequently facilitated the transfer of photo-induced charge carriers through the formed tandem n-n heterojunctions amongst TiO2−x, Bi4V2O11, and BiVO4 components. In addition to high photocatalytic activities, the TOVBBV-2 photocatalyst demonstrated good photostability and durability after concurrent applications. This work recommends the TOVBBV photocatalyst for facile photocatalytic treatment of pollutants owing to its simple preparation route, high degradation outcomes, and robust structure for practical applications.

Multifunctional layered bismuth oxychloride/amorphous antimony oxide hetero-hybrids as superior photocatalyst and potassium ion storage materials

In this work, a multifunctional BiOCl/amorphous antimony oxide (AAO) hetero-hybrid with the molar ratio of Bi3+/Sb3+ in 1/3 (1-BOC/3-AAO) is successfully developed by the scalable ball-milling strategy and demonstrates an exceptional visible light photocatalytic degradation performance of RhB and superior anodic potassium ion storage performance for potassium ion batteries over other reported BOC materials, benefitted from the large specific surface area, narrow band gap, improved utilization of visible light, effectively suppressed recombination and highly enhanced transfer efficiency of the photogenerated charge carriers of the hetero-hybrid. Under the light irradiation of a 300 W xenon lamp without and with an optical filter (≥ 420 nm), almost 100.0% RhB in the aqueous solution can be degraded after 20 mins. At the same time, the as-prepared 1-BOC/3-AAO also demonstrate a superior potassium ion storage over other reported BOC-based materials. The potassium half-cell assembled with as-prepared 1-BOC/3-AAO as working electrodes can deliver an initial charge capacity of 505.3 and 395.9 mAhg−1 at the current density of 100 and 500 mAg−1, meanwhile, maintains 427.7 after 500 cycles at 100 mAg−1and 316.9 mAhg−1 after 800 cycles at 500 mAg−1, respectively. Therefore, BOC/AAO hetero-hybrids will be a promising candidate commercial catalyst for degradation of organic pollutes within the industrial waste water and promising high performance anode materials for potassium ion batteries.

Rational design, fabrication, optical properties and high-efficiency visible-light photocatalytic degradation performance for organic pollutants of Eu:Bi2WO6/CdS nanostructures

Over the past few years, semiconductor materials (especially bismuth tungstate) exhibiting unique environment purification and energy conversion capacities arouse huge attention as impacted by issues of environmental pollution and energy shortage, whereas its application is restricted by the problems of high carrier recombination rate and unsatisfactory degradation efficiency. In this study, Eu:Bi 2 WO 6 nanostructures containing Eu ions of different concentrations were synthesized with a chemical solution method, and CdS was generated on the surface of Eu:Bi 2 WO 6 nanostructures in situ epitaxial to synthesize the Eu:Bi 2 WO 6 /CdS composites. The effects of Eu doping concentration on the crystal structure, chemical composition, local structure, optical properties and visible-light photocatalytic properties exhibited by Eu:Bi 2 WO 6 /CdS nanostructures were studied more specifically, and the Eu doping behavior on the improvement mechanisms for optical and photocatalytic performance exhibited by Eu:Bi 2 WO 6 /CdS nanostructures was clarified. The robust PL emission peak at about 390 nm and weak emission peak at nearly 450 nm are attributed to the exciton emission and defect state of Bi 2 WO 6 /CdS nanostructure, respectively. As indicated from the mechanism insights, the reasonable introduction of Eu 3+ could alter the band gap of the photocatalyst, and the epitaxial CdS could decrease the recombination probability of electron and hole in the Bi 2 WO 6 /CdS, while improving the photocatalytic activity. This study supplies new occasions for rational excogitation and better comprehending of atomic-scale complicated structures for applications in numerous fields (e.g., energy and environmental protection).

One-step hydrothermal synthesis of Ag2Se/amorphous MoSex heterojunction with enhanced visible-light photocatalytic degradation performance

The application of MoSe2 in the field of photocatalysis is limited by the lack of active sites and high carrier compound efficiency. The above shortcomings can be effectively solved by introducing amorphous structure and constructing heterojunction. Ag2Se/amorphous MoSex (a-MoSex) composites were successfully prepared by simple, low-cost one-step hydrothermal method for the first time, and the photocatalytic degradation efficiency was characterized by the degradation of methylene blue under visible light under visible light, the photocatalytic degradation efficiency of Ag2Se/a-MoSex composites is up to 95.7%.

Fabrication of CdS/ZnS/g-C3N4 Composites for Enhanced Visible-Light Photocatalytic Degradation Performance

Constructing a heterojunction is an ideal way to modify the photocatalytic efficiency of semiconductor photocatalysts. In this paper, CdS/ZnS/g-C3N4 (CZG) ternary composites with different mass ratio of CdS (10%, 20%, 30%) were prepared by cation exchange method using as-synthesized ZnS/g-C3N4 and Cd(NO3)2·6 H2O as the starting materials. The composition and optical properties were investigated by XRD and photoluminescence spectra (PL). The results showed the ternary heterojunctions possessed faster photo-induced electrons/holes separation efficiency. The photocatalytic experiments exhibited that the obtained ternary composite materials exhibited enhanced visible-light photodegradation efficiency for the degradation of MO aqueous solution. Among the ternary composite materials, the CZG-10% composite displayed the highest photocatalytic performance of 68.52%. The enhanced photodegradation efficiency could be ascribed to the reasonable design of the heterojunction.

One-Step Fabrication of CdS/Ag <sub>2</sub>S Heterojunction Composites and its Enhanced Visible Light Photocatalytic Degradation Performance

One-Step Fabrication of CdS/Ag <sub>2</sub>S Heterojunction Composites and its Enhanced Visible Light Photocatalytic Degradation Performance

Synthesis and characterization of type-II p(CuxSey)/n(g-C3N4) heterojunction with enhanced visible-light photocatalytic performance for degradation of dye pollutants

The current work investigated a synergetic effect of graphitic carbon nitride (g-C3N4) with different concentrations (5, 10, 1nd 15 w%) on the visible-light photocatalytic activity of the copper-selenide (CuxSey) nanostructures. Morphology and structure of the nanostructures were CuSe hexagonal nanodiscs decorated with Cu3Se2 nanoparticles (NPs). UV–vis spectra showed a higher absorption intensity for the CuxSey/g-C3N4 nanocomposites. Mott-Schottky (MS) experiments indicated a p-type behavior for the CuxSey nanostructures forming a p-n heterojunction with n-type g-C3N4. The photocatalytic activity measurements showed that the g-C3N4 with a 5% concentration had a significant synergetic role to improve the photocatalytic performance of the nanostructures. Brunauer–Emmett–Teller (BET) indicated the samples included mesostructure but the g-C3N4 could not improve their textural properties. The Fermi level offset of the p-n heterojunction led to an internal electric field caused the electrons and holes to move in opposite directions. Thus we encountered with a strong electron-hole separation in this heterojunction. This was the most important factor to enhance the photocatalytic performance of the CuxSey/g-C3N4. Finally, the examination of the photocatalytic activity showed that the hydroxyl radicals (OH) were the most important factors during the redox process of the dye.

Facile fabrication of phosphorus-doped g-C3N4 exhibiting enhanced visible light photocatalytic degradation performance toward textile dye

Phosphorus-doped graphitic carbon nitride (P-g-C3N4) was facilely fabricated by in situ thermal copolymerization of urea and triphenylphosphine source materials. The P-g-C3N4 exhibited an enhanced photocatalytic performance than pristine g-C3N4 counterpart for the degradation of rhodamine B and acid blue D-2BR textile dye under visible light irradiation. X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption-desorption isotherms, X-ray photoelectron spectra (XPS), and diffuse reflection spectroscopy (DRS) techniques were used to characterized the structure and property of P-g-C3N4 photocatalyst. The phosphorus doping enhanced visible light harvesting and surface area, but also substantially changed the electronic property of g-C3N4 material that could suppress the recombination of photogenerated charge carriers, and thus improved photocatalytic performance.

A magnetically separable plate-like cadmium titanate-copper ferrite nanocomposite with enhanced visible-light photocatalytic degradation performance for organic contaminants.

A novel magnetic cadmium titanate–copper ferrite (CdTiO3/CuFe2O4) nanocomposite, in which spherical CuFe2O4 nanoparticles were loaded onto the surface of CdTiO3 nanoplates, was successfully synthesized via a sol–gel hydrothermal route at 180 °C. The structure, morphology, magnetic and optical properties of the as-prepared nanocomposite were respectively characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) spectroscopy, transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) surface area analysis, UV-visible diffuse reflectance spectroscopy (DRS), vibrating sample magnetometry (VSM) and photoluminescence (PL) spectroscopy. The photocatalytic activity of this novel CdTiO3-based magnetic nanocomposite was investigated for the degradation of organic dye pollutants such as methylene blue (MB), rhodamine B (RhB), and methyl orange (MO) in the presence of H2O2 under visible light irradiation. The results showed that the photocatalyst completely degraded three dyes within 90–100 min. Compared with pure CdTiO3 and CuFe2O4, the heterogeneous CdTiO3/CuFe2O4 nanocomposite exhibited significantly enhanced photocatalytic efficiency. On the basis of the results of the OH trapping and photoluminescence (PL) experiments, the enhanced photocatalytic performance was mainly ascribed to the efficient separation of photo-induced electron–hole pairs and the formation of highly active hydroxyl radicals (OH) species in the CdTiO3/CuFe2O4 photocatalytic oxidation system. The PL measurements of the CdTiO3/CuFe2O4 nanocomposite also indicated an enhanced separation of photo-induced electron–hole pairs. Moreover, the nanocomposite could be easily separated and recycled from contaminant solution using a magnet without a decrease in their photocatalytic activity due to their good magnetic separation performance and excellent chemical stability. Based on these findings, CdTiO3/CuFe2O4 nanocomposite could be a promising visible-light-driven magnetic photocatalyst for converting solar energy to chemical energy for environmental remediation.

Sol-Gel Hydrothermal Synthesis and Visible Light Photocatalytic Degradation Performance of Fe/N Codoped TiO₂ Catalysts.

Using Ti(OC4H9)4 as a precursor, Fe(NO3)3⋅9H2O as the source of iron, and NH4NO3 as the source of nitrogen, an Fe/N codoped TiO2 catalyst was prepared using a sol-gel hydrothermal method. The as-prepared powders were characterized using X-ray powder diffraction, electron spectroscopy for chemical analysis, Fourier-transform infrared spectroscopy, and ultraviolet-visible spectrophotometry. Fe and N codoping resulted in decreased crystallite size and increased specific surface area. Results of the photocatalytic degradation of acid orange 7 (AO7) in a continuous-flow fluidized-bed reactor indicated that the maximum decolorization (more than 90%) of AO7 occurred with the Fe/N-TiO2 catalyst (dosage of 20 g/L) when a combination of visible light irradiation for 10 h HRT (hydraulic retention time), and a heterogeneous system was used. The AO7 degradation efficiency was considerably improved by increasing the hydraulic retention time from 2.5 to 10 h or by reducing the initial AO7 concentration from 300 to 100 mg/L. The reaction rate increased with the light intensity and the maximum value occurred at 35 mW/cm2; moreover, the efficiency of the AO7 degradation increased when the pH decreased with maximum efficiency at pH 3.

Enhancing visible light photocatalytic degradation performance and bactericidal activity of BiOI via ultrathin-layer structure

Hollow flower-like BiOI photocatalyst (h-BiOI) was obtained via a facile solvothermal method, which consists of ultrathin nanosheets with a thickness of about 2nm. The structures and morphologies of as-prepared products were characterized by XRD and SEM and the absorption properties were determined by DRS. h-BiOI exhibit a more positive VB band than that of bulk BiOI (b-BiOI), which suggests a much stronger oxidation ability of the former. Therefore, h-BiOI displays completely degradation ability towards RhB under visible light irradiation while b-BiOI only decomposes RhB into segmental fragments under the same conditions. In addition, h-BiOI exhibits significantly higher antibacterial performances than b-BiOI under LED (470nm) light irradiation. Besides the higher oxidation ability, the excellent photocatalytic activity of h-BiOI may be due to the ultrathin nanosheet, which takes less time for the photogenerated electrons and holes to reach the surface and therefore reduce their recombination.

One-step synthesis of flowerlike C/Fe2O3 nanosheet assembly with superior adsorption capacity and visible light photocatalytic performance for dye removal

A flowerlike C/Fe2O3 nanosheet assembly, in which the surface is coated by a hydrothermal carbon (HTC) layer with thickness of 3–5 nm, has been successfully synthesized via a one-step hydrothermal strategy. Due to the coated HTC layer, the C/Fe2O3 nanosheet assembly exhibits the significantly enhanced efficiency for the removal of organic pollution, including the physically adsorption capacity and the visible-light photocatalytic degradation performance. The photocatalytic activity of the C/Fe2O3 nanosheet assembly is almost 4.6 times as high as that of the pure Fe2O3 sample for methylene blue degradation under the visible light irradiation. Besides the adsorption capacity, it is also demonstrated that the HTC coating can facilitate the surface electron migration, resulting in the increased separation efficiency of photogenerated electron/hole pairs. In terms of those experimental results, a possible photocatalytic mechanism of the C/Fe2O3 nanosheet assembly has been proposed and discussed.

Polyaniline-doped TiO2/PLLA fibers with enhanced visible-light photocatalytic degradation performance

A simple and practical strategy has been developed for preparing polyaniline(PANi)-doped TiO2/poly(l-lactide) (P@TiP-C) fibers by a combination of coaxial-electrospinning and in-situ polymerization. The TiO2/PLLA composite fibers with TiO2 located on the surface were fabricated by coaxial-electrospinning, with PLLA as the core phase and a dispersion of TiO2 particles, a well-known photocatalyst, in the sheath phase. The aniline monomers were also located in the core phase and in-situ polymerized by ammonium persulfate (APS) after electrospinning. SEM images show that TiO2 particles were located on the surface of PLLA fibers. Photocatalytic degradation tests show that the P@TiP-C fibers exhibit enhanced photocatalytic activity for degradation of methyl orange under visible light, likely due to the synergistic effect of PANi and TiO2.

Ultrasonic-assisted preparation of plasmonic ZnO/Ag/Ag2WO4 nanocomposites with high visible-light photocatalytic performance for degradation of organic pollutants

In this work, plasmonic ternary ZnO/Ag/Ag2WO4 nanocomposites as efficient visible-light-driven photocatalysts prepared by a facile ultrasonic-irradiation method. The as-prepared samples were characterized by XRD, SEM, TEM, EDX, XPS, UV–vis DRS, FT-IR, and PL techniques. The photocatalytic performance of the prepared ZnO/Ag/Ag2WO4 nanocomposites were evaluated by photodegradations of rhodamine B, methylene blue, methyl orange, and fuchsine under visible-light irradiation. The optimal nanocomposite with 15wt% of Ag/Ag2WO4 to ZnO showed the highest photocatalytic activity for RhB degradation, which is about 95 and 19 times higher than those of the Ag/Ag2WO4 and ZnO samples, respectively. The highly enhanced activity of the ZnO/Ag/Ag2WO4 (15%) nanocomposite was attributed to the surface plasmon resonance effect of metallic silver and the formation of heterojunctions between the counterparts, which effectively suppresses recombination of the photogenerated charge carriers. Lastly, the plasmon-enhanced photocatalytic mechanism associated with the ZnO/Ag/Ag2WO4 nanocomposites was discussed.

Sol-Gel Process Synthesis and Visible-Light Photocatalytic Degradation Performance of Ag Doped K2Ti4O9

K2Ti4O9 and Ag-K2Ti4O9 were synthesized by using Ti(OC4H9)4 and KNO3 as precursor via Sol-Gel process. The influences of silver ion doping on structure, absorbance performance and catalytic performance of K2Ti4O9 have been studied. The results suggested that the structure of K2Ti4O9 doped with Ag+ remained unchanged, but its absorbance performance under visible light improved, resulting in its increased photocatalytic activity. Moreover, photocatalytic activity of K2Ti4O9 doped with 0.5 mol%Ag+ is the best when pH value was 7 with 1.5g/L fed catalyst and 10ml/L MB as well as illumination time of 2h, which can obtain the photocatalytic efficiency of 78.43% in the visible light.

Flexible polyaniline-coated TiO2/SiO2 nanofiber membranes with enhanced visible-light photocatalytic degradation performance

A simple and practical strategy has been developed for preparing polyaniline (PANi) coated TiO2/SiO2 nanofiber membranes by a combination of electrospinning, calcination and in situ polymerization. TiO2/SiO2 (TS) nanofibers are fabricated by electrospinning, followed by calcination. Then they are used as template for in situ polymerization of aniline monomers. SEM images show that PANi nanoparticles thus formed can be densely and uniformly coated on the surface of TS nanofibers. Photocatalytic degradation tests show that the as-prepared nanofiber membranes exhibit enhanced photocatalytic activity for degradation of methyl orange under visible light, which may be due to the synergistic effect of PANi and TiO2. Furthermore, the effect of polymerization time on the morphology and photocatalytic activity of the membrane is investigated. The free-standing membrane is flexible and easy to handle, which is promising for potential applications in photocatalysis and water remediation fields.