Visible Light Photocatalytic Applications Research Articles

The bifunctional performance analysis of synthesized Ce doped SnO2/g-C3N4 composites for asymmetric supercapacitor and visible light photocatalytic applications

Cerium (Ce) doped SnO2/g-C3N4 composites were synthesized by a facile hydrothermal method. The obtained Ce doped SnO2/g-C3N4 composites were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV–visible spectroscopy (UV–Vis), scanning electron microscope (SEM), energy dispersive spectra (EDS), elemental mapping and X-ray photoelectron spectroscopy (XPS). An electrode made of Ce doped SnO2/g-C3N4 exhibited a maximum specific capacitance of 274 F/g at 1 A/g current density. The supercapacitor device fabricated by using Ce-SnO2/g-C3N4//Activated Carbon as electrodes has showed an energy and power densities of 39.3 W h kg−1 and 7425 W kg−1. The asymmetric device gives the retention of 84.2% after completing 5000 cycles. When the same, Ce-SnO2/g-C3N4, composite is used as a photo-catalyst for reduction of methylene blue dye under visible light irradiation, exhibits a higher degradation efficiency of 98% which is higher efficiency compared to all other synthesized samples.

Preparation and measurement of properties of BiOBr/BiOCl/PANI ternary nanocomposite for highly efficient visible light photocatalytic applications

In this paper, we report the synthesis of the BiOBr/BiOCl/PANI ternary nanocomposite using a simple co-precipitation method. The modified photocatalyst produced was characterized by the FT-IR, FE-SEM equipped with EDS (as a Map), TEM, XRD, PL, Raman, and UV–Vis DRS analytical techniques. The synergetic effect of PANI and surface defects in nanoplates can prolong the recombination rate of photo-generated charge carriers. Thus, photocatalytic and photoelectrochemical activities of samples have been studied. Then, the methyl orange (MO) degradation performance of PANI/BiOBr and BiOBr/BiOCl/PANI was investigated under visible light irradiation. The lamp used to simulate sunlight in this photocatalytic study process was power down white light (5-W LED), less reported. The results got exhibited that the as-prepared BiOBr/BiOCl/PANI (90:10, Bi:PANI) nanocomposite showed a higher photocatalytic efficiency. Based on the scavenger tests, ·O2− played a significant role in the degradation of MO. The connection between BiOBr, BiOCl, and PANI improved photocatalytic activity, which enhanced migration rate of the photo-generated electrons besides limiting the recombination of photo-generated electron–hole pairs.

Microwave-assisted synthesis of various Cu2O/Cu/TiO2 and CuxS/TiO2 composite nanoparticles towards visible-light photocatalytic applications

Microwave-assisted Cu2O/Cu/TiO2 and CuxS/TiO2 composite nanoparticles were successfully prepared with or without several kinds of supporting chemical linkers between Cu and Ti. As for the synthesis of cube-shaped Cu2O/Cu/TiO2 composite nanoparticles, mixed alcohols containing ethyl alcohol and benzyl alcohol were used without any additives under 800–900 W microwave. CuxS/TiO2 composite particles were prepared using two kinds of experimental procedures. One method was to use l-cysteine additive to interconnect TiO2 and CuxS in neutral aqueous solution. The other method was to use thiourea under NaOH basic condition. The particle morphology was confirmed with TEM images and the homogeneous distribution of elements including Ti, O, Cu, and S were proved by TEM-EDS mapping method. XRD patterns clarified high crystallinity of anatase TiO2 and Cu salts. Crystal structures of Cu2O and CuxS varied depending on the relative compositions and synthetic procedures. UV–visible spectra showed high absorbance at visible region according to the Cu species incorporated in the composite particles. The photocatalytic performance of each composite sample was compared both by monitoring the degradation of Rhodamine B under UV irradiation and methyl orange under visible-light irradiation. Under UV irradiation, the amount of copper species seems to hinder the catalytic performance, whereas Cu2O and Cu inside ternary Cu2O/Cu/TiO2 composites enhance the performance under visible-light irradiation.

Facile preparation of Bi-doped ZnO/β-Bi2O3/Carbon xerogel composites towards visible-light photocatalytic applications: Effect of calcination temperature and bismuth content

This work aimed to study the development and properties of Bi-doped ZnO/β-Bi2O3/Carbon xerogel composites towards visible light photocatalysis applications. The materials were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, dispersive energy spectroscopy, infrared spectroscopy, nitrogen adsorption isotherms, Raman spectroscopy, diffuse reflectance spectroscopy and X-ray photoelectron spectroscopy. The photocatalytic activity of the developed composites was evaluated through the photodegradation of the 4-chlorophenol molecule and by chronoamperometry tests. The results obtained show that the calcination temperature poses a major influence in the final structure of the materials developed. The calcination temperature of 600 °C resulted in the formation of the β-Bi2O3 and Bi0 phases, consequently enhancing the photocatalytic activity of the composites due to the increased charge mobility provided by the heterojunctions between zinc oxide, carbon xerogel, bismuth oxide and metallic bismuth. The composite with intermediate bismuth composition (XC/ZnO–Bi2O3 5%) displayed the best photocatalytic response among the materials tested, which was confirmed by its increased photocurrent generation capability. The photocatalytic mechanism is highly dependent in the generation of hydroxyl radicals and the composite presents good reusability properties.

Green synthesis of zinc oxide incorporated nanocellulose with visible light photocatalytic activity and application for the removal of antibiotic enrofloxacin from aqueousmedia

Abstract Purpose of this study is to report the green synthesis of a visible light driven photocatalyst Zincoxide incorporated Nanocellulose (ZnO/NC) from Tinospora Cordifolia plant stem extract and Sugarbagasse for the photodegradation of Enrofloxacin (EF), an antibiotic widely used in the veterinary medicines to treat animals for bacterial infections. By incorporating nano zinc oxide (ZnO) with NC, the band gap was enhanced to visible region. Thus the degradation of the EF was achieved under the visible light. Photo degradation was due to electron hole interaction. The photocatalyst ZnO/NC was characterized using FTIR, XRD, SEM and TEM. Various parameters such as the effect of pH, illumination time, amount of catalyst loaded and initial antibiotic concentration for the photodegradation of antibiotic EF was investigated. The optimum pH was found to be 5 and dose of the ZnO/NC was optimized as 0.20 g/L. Equilibrium was attained at 120 min and achieved a maximum degradation efficiency of 97%.

Fabrication of g-C3N4/TiO2 photocatalysts with a special bilayer structure for visible light photocatalytic application

Photocatalytic technology is a new technique for environmental purification and solar energy conversions. The development of new and efficient photocatalysts has been a research hotspot for several years and the fabrication of composite photocatalyst has attracted wide attention. Herein, g-C3N4/TiO2 photocatalyst with a special bilayer structure has been synthesized under mild solvothermal conditions with TiO2 flake as the substrate material. The combination of TiO2 and g-C3N4 effectively increased the specific surface area of the composite and was conducive to the synergistic effect. The time of solvothermal reaction influences the binding mode of g-C3N4 and TiO2, which in turn affects the photocatalytic activity. The photodegradation rate of methylene blue (MB) by g-C3N4/TiO2 composite reached 97.61 % under visible light irradiation, which was 1.46 and 1.98 times higher than those of pure g-C3N4 and TiO2, respectively. The improvement of photocatalytic performance is mainly attributed to the enhanced separation efficiency of photogenerated electron-hole pairs caused by the construction of heterojunctions, which has been confirmed by electrochemical impedance spectroscopy and optical transient current spectrum. Furthermore, the main active species in photocatalytic system were determined by radical trapping experiments and the photocatalytic mechanism of the composite photocatalytic system was further speculated.

Fabrication of novel fibrous BiVO4/CdS heterostructures by electrospinning method for efficient visible light photodegradation

Novel fibrous BiVO4/CdS heterostructures were fabricated for photodegradation of Rhodamine B (RhB) dyes. Caterpillar shaped BiVO4 nanofibers were produced by electrospinning and post calcinations. Controllable quantity of CdS nanoparticles were uniformly decorated on BiVO4 fiber surface by electrostatic interaction. Both the BiVO4 nanofibers and CdS nanoparticles present high crystallinity. The integration of CdS can significantly enhance the absorption of visible light and separation efficiency of photo-generated charge in BiVO4/CdS composites. As a result, the photocatalytic efficiency and apparent reaction rate constant of the optimized BiVO4/CdS-2 display 1.6 and 3 times as high as that of pure BiVO4 after 120 min irradiation under visible light, respectively. Moreover, the BiVO4/CdS-2 nanofibers show good stability for repeated visible light photocatalytic application. The scavengers added photocatalytic experiments indicate the crucial roles of •O2− and h+ for the degradation process, and a Z-scheme photocatalytic mechanism was proposed for the BiVO4/CdS system. Due to the simple and low-cost synthetic method, the fibrous BiVO4/CdS catalysts are suitable for practical applications.

Template Thermolysis to Create a Carbon Dots-Embedded Mesoporous Titanium-Oxo Sulfate Framework for Visible-Light Photocatalytic Applications.

An organo-templated titanium-oxo sulfate of the formulation (H2nep)[TiO(SO4)2] (denoted as TiOS, nep = N-ethylpiperazine) was synthesized under solvent-free conditions. The framework of TiOS is assembled from the [TiO(SO4)2]n2n- infinite chains interconnected by the H2nep cations through H-bond networks. After thermal treatment under vacuum conditions, the organic template H2nep was partially decomposed and converted into N-doped carbon dots (N-CDs), resulting in the N-CDs@TiOS composite material with retained crystallinity of the parent TiOS. The thermolysis of organic templates generates meso-cavities in the framework, rendering N-CDs@TiOS with a mesoporous structure. Photoelectrochemical and photocatalytic experiments show that the presence of N-CDs substantially improved visible-light-driven photocatalytic activity of N-CDs@TiOS compared to that of TiOS. The template thermolysis strategy gives an effective approach to construct the CDs-sensitized Ti-based mesoporous open-framework materials for visible-light photocatalytic applications.

Design of nanoscaled heterojunctions in precursor-derived t-ZrO2/SiOC(N) nanocomposites: Transgressing the boundaries of catalytic activity from UV to visible light

In this work, nanocomposites made of nanosized zirconia crystallized in situ in an amorphous silicon oxycarbo(nitride) (SiOC(N)) matrix have been designed through a precursor route for visible light photocatalytic applications. The relative volume fraction of the starting precursors and the pyrolysis temperatures not only influences the phase fraction of zirconia crystallites but also stabilizes the tetragonal crystal structure of zirconia (t-ZrO2) at room temperature. The presence of carbon in interstitial sites of zirconia and oxygen vacancy defects led to drastic reduction in the band gap (2.2 eV) of the nanocomposite. Apart from being a perfect host avoiding sintering of the active phase and providing mechanical stability, the amorphous matrix also reduces the recombination rate by forming heterojunctions with t-ZrO2. The reduction in band gap as well as the formation of heterojunctions aids in harnessing the visible light for photocatalytic activity.

One-pot microwave-assisted green synthesis of amine-functionalized graphene quantum dots for high visible light photocatalytic application

Nowadays, graphene quantum dots (GQDs) have gained a huge interest in the field of visible-range photocatalysts because of their tunable band gap and stable photochemical properties. In this work, amine-functionalized GQDs (AGQDs) were successfully prepared by one-step microwave-assisted conversion of glucose, H 2 O 2 , and NH 3 solution. The obtained quantum dots possess the high quality of graphene structure with the average size of 3.78 nm as well as exhibit a strong green fluorescence with a high quantum yield. Interestingly, the amine-functionalized dots perform outstanding visible-light absorption. To further investigate photocatalytic properties, a composite of AGQDs and TiO 2 was then prepared by a simple mixing route. The hybrid material showed high catalytic activity of dye degradation under visible light irradiation, which indicates the key role of AGQDs in enhancing light absorption and induced electron–hole separation. The current study may open a new way for construction of effective visible light photocatalytic systems with a cost-effective, simple approach.

Anchoring lead-free halide Cs3Bi2I9 perovskite on UV100–TiO2 for enhanced photocatalytic performance

Halide perovskites have shown great potential in photocatalytic applications. In order to enhance the charge transportation efficiency, the chemical stability, and the light absorption ability, we anchored a lead-free halide perovskite (Cs3Bi2I9) on UV100–TiO2 nanoparticles to build a visible-light active photocatalysts. The as-prepared material exhibited excellent stability and a remarkable yield for photocatalytic oxidation of methanol to formaldehyde under visible light irradiation. The photocatalyst was characterized using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, Transmission electron microscopy, X-ray photoelectron spectroscopy, ultraviolet–visible diffuse reflectance spectroscopy, Brunauer–Emmett–Teller surface area measurement, and photoelectrochemical properties. The analyses confirmed a remarkable improvement of visible-light absorption, a favorable decrease in the recombination of photoinduced charge carriers, and a suitable bandgap for visible-light photocatalytic applications. Recycle experiments showed that the composites still presented significant photocatalytic activity after three successive cycles. A possible underlying mechanism of the composite accounting for the enhanced photocatalytic activity under visible light irradiation was proposed.Our study aims to open new possibilities of using lead-free halide perovskites for photocatalytic applications.

Production of N-doped anatase TiO2 on TiN-coated Ti substrates by plasma electrolytic oxidation for visible-light photocatalysts

N-doped TiO2 exhibiting visible-light photocatalytic activity is useful for many environmental and energy applications. In this work, N-doped anatase TiO2 coatings were facilely produced by plasma electrolytic oxidation using two types of nitrogen doping sources including the TiN seeding layers and the electrolytes consisting of (NaPO3)6 and NaOH mixed with various NH4OH concentrations. The TiN seeding layers were deposited on Ti foils by a unique air-based sputtering technique. Effects of the TiN seeding layers and the NH4OH concentrations added in the electrolytes on the characteristics and the resulting visible-light photocatalytic activity of obtained N-TiO2 coatings were investigated. Enhanced bandgap narrowing and visible-light photocatalytic activity for the coatings were achieved by using the TiN seeding layer and the optimum NH4OH concentration added in the electrolytes. The synergistic effects of both nitrogen doping sources were discussed. The facile controlled growth of N-doped anatase TiO2 coatings with uniform porous surface morphologies has great potentials in visible-light photocatalytic applications.

A novel CuInS2/m-BiVO4 p-n heterojunction photocatalyst with enhanced visible-light photocatalytic activity

Novel CuInS2/m-BiVO4 composites with different mass ratios (CuInS2 to m-BiVO4 = 1:3, 1:1, and 3:1) were synthesized and their potential visible-light photocatalytic applications for photodegradation of some organic dyes (methylene blue, rhodamine B, and methyl orange) and inactivation of bacteria (Pseudomonas aeruginosa) were investigated. CuInS2/m-BiVO4 with a mass ratio of 1:3 exhibited better photocatalytic degradation of methylene blue and antibacterial activity than those of either pure CuInS2 or m-BiVO4. Moreover, this composite photocatalyst showed different photocatalytic selectivity in terms of the organic dye degradation. Salicylic acid was also used to test the photocatalytic activity of this composite to clarify the dye sensitization effect. The photoelectrochemical (PEC) properties of the CuInS2/m-BiVO4 photoelectrode, evaluated by linear sweep voltammetry (LSV) measurement, revealed that the composite photoelectrode exhibited higher current density and onset potential in comparison with the m-BiVO4 photoelectrode. In addition, the electrochemical impedance spectroscopy (EIS) measurement also proved a faster rate of charge transfer at the electrode/electrolyte interface. The enhancement of photocatalytic and PEC activities of the CuInS2/m-BiVO4 composite was revealed not only that the CuInS2/m-BiVO4 composite extended light absorption in the visible light region, but also that the formation of a p-n heterojunction could promote photogenerated charges as well as facilitate effective charge separation and transportation between the CuInS2 and m-BiVO4 contact interface.

TiO2@g-C3N4 core/shell spheres with uniform mesoporous structures for high performance visible-light photocatalytic application

Abstract Mesoporous g-C3N4 nanosheets (MCN) with uniform pore size were utilized to decorate mesoporous TiO2 spheres (TSs) to form a core-shell heterojunction photocatalyst containing uniform mesopores. Moreover, the mesoporous g-C3N4 nanosheets served as shells for composites, in addition to playing a pivotal function for the regulation of the pore structure of the composite. The mesoporous TiO2@g-C3N4 core/shell structure having a uniform pore size exhibited high surface area of ∼134 m2/g. This coupled material with improved porosity, not only led to increased visible-light absorption but also led to the enhanced charge generation/separation. In addition, it showed a lengthy cycling stability with highly active visible-light efficiency to degrade Rhodamine B (RhB) dye.

Facile synthesis of controllable carbonate-doped TiO2 microspheres for visible light photocatalytic applications

Mesoporous carbonate-doped TiO2 microspheres were prepared by a facile solvothermal route combining a low-temperature annealing process. XPS, TG, and FTIR analysis revealed the presence of carbonate species on TiO2 surface, which extended the optical absorption of the TiO2 microspheres to the visible region. The carbonate-doped T200 microspheres exhibited much higher photocatalytic degradation of MO activity compared with non-doped T400 microspheres under visible light illumination. By adjusting initial titanium precursor concentration and reaction time, the best photocatalytic performance of carbonate-doped T200 microspheres was obtained. In addition, carbonate-doped T200 microspheres also displayed good photocatalytic disinfection efficiency towards Escherichia coli under visible light exposure. Our study revealed that the carbonate-doped TiO2 microspheres would be applied in the water treatment for the degradation of organic pollutants and disinfection of bacteria.

Synthesis of YAG:Ce/ZnO core/shell nanoparticles with enhanced UV-visible and visible light photocatalytic activity and application for the antibiotic removal from aqueous media

Abstract

Reduced Graphene Oxide/TiO2 Nanocomposite: From Synthesis to Characterization for Efficient Visible Light Photocatalytic Applications

In this study, a green and facile thermal reduction of graphene oxide using an eco-friendly system of d-(+)-glucose and NH4OH for the preparation of reduced graphene oxide was described. The obtained reduced graphene oxide dispersion was characterized by SEM, Dynamic Light Scattering, Raman and X-Ray Photoelectron Spectroscopy. TiO2 nanoparticles and reduced graphene oxide nanocomposites were successively prepared and used in the preparation of heterogeneous photocatalysts that were characterized by Atomic Force Microscopy and Photoluminescence Spectroscopy and subsequently tested as visible light photocatalysts for the photodegradation of Alizarin Red S in water as target pollutant. Obtained results of photocatalytic tests regarding the visible light photocatalytic degradation of Alizarin Red S demonstrated that the use of reduced graphene oxide in combination with TiO2 led to a significant improvement for both adsorption of Alizarin Red S on the catalyst surface and photodegradation efficiencies when compared to those obtained with not doped TiO2.

Facile Solvothermal Synthesis of CuCo₂S₄ Yolk-Shells and Their Visible-Light-Driven Photocatalytic Properties.

In this present work, we synthesized a yolk-shell shaped CuCo2S4 by a simple anion exchange method. The morphological and structural properties of the as-synthesized sample were characterized using X-ray diffraction (XRD), UV-vis diffuse reflectance spectra (UV-vis DRS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The SEM and TEM results confirmed that the uniform yolk-shell structure was formed during the solvothermal process. The band gap was about 1.41 eV, which have been confirmed by UV–vis DRS analysis. The photocatalytic property was evaluated by the photocatalytic degradation of methylene blue (MB) dye as a target pollutant under the visible-light irradiation. The experimental results confirmed the potential application of yolk-shell shape CuCo2S4 in visible-light photocatalytic applications.

Construction, enhanced visible-light photocatalytic activity and application of multiple complementary Ag dots decorated onto Ag2MoO4/AZO hybrid nanocomposite

It is of urgency to develop novel and high-efficient visible-light photocatalysts to eliminate antibiotics and organic pollutants rapidly in sewage. Therefore, the silver molybdate/aluminum atoms-doped zinc oxide (Ag2MoO4/AZO) nanocomposite was prepared by in situ deposition, and then the Ag dots were decorated on this nanocomposite surface via photo-reduced reaction forming a multiple complementary Ag@Ag2MoO4/AZO hybrid nanocomposite. The photogenerated electrons of AZO transferred to Ag2MoO4 surface, which solved the optical instability of Ag2MoO4 material increasing the recyclability. The photocatalytic efficiency of Ag@Ag2MoO4/AZO nanocomposite still remained 90.0% after eight runs. Meanwhile, the Ag dots decorated on the Ag@Ag2MoO4/AZO nanocomposite surface decreased the band gap and broadened the visible-light absorption range, promoting the efficient separation of photogenerated carriers. Because of the synergistic complementary effect of Ag dots and AZO solid solution, the Ag@Ag2MoO4/AZO hybrid nanocomposite showed excellent photocatalytic activity on organic pollutants compared to AZO and Ag2MoO4 material (282.3% and 422.7% improvement, respectively). In addition, the gatifloxacin was completely degraded to CO2 and H2O within 40 min, indicating that the Ag@Ag2MoO4/AZO hybrid nanocomposite also has excellent application in the treatment of antibiotics.

One-pot hydrothermal synthesis of CuCo2S4/RGO nanocomposites for visible-light photocatalytic applications

CuCo2S4/reduced graphene oxide (RGO) nanocomposites with varying amount of RGO loadings were synthesized using a simple hydrothermal method. l-Cysteine has been used as a bio-sulfur source to synthesize CuCo2S4 nanoparticles. Scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) images showed that the CuCo2S4 nanoparticles uniformly decorated the entire surface of the RGO sheets. The results of photo electrochemical studies revealed that the incorporation of RGO could improve the effective electron transportation, which leads to higher photocatalytic activity. The highest degradation efficiency toward photodegradation of malachite green was achieved with 3% of RGO loading in the CuCo2S4 matrix. Furthermore, based on experimental results, the underlying mechanism for photocatalysis was proposed and discussed. This study demonstrates that the CuCo2S4/(RGO) nanocomposites could be used as a green photocatalyst for environmental applications.