Effects Of Visible Light Absorption Research Articles

All-solid-state Z-scheme nanojunction PW12/Ag/ZnO photocatalyst: Effective carriers transfer promotion and enhanced visible light driven

By coupling two semiconductors with favorable band gap, ZnO (PS I) and Keggin-type tungstophosphate (PW12, PS II), an interesting all-solid-state Z-scheme photocatalyst PW12/Ag/ZnO has been designed and synthesized. In the developed composite PW12/Ag/ZnO, noble metal silver nanoparticle as an efficient conductor constructs an efficient spatial charge separation and carriers transfer process. By controlling reaction conditions, the UV–Vis absorption of Ag nanoparticles in the designed all-solid-state Z-scheme complex is gradually improved from about 400 nm to near infrared region. Benefited from its effective visible light absorption, the developed photocatlyst exhibits favorable UV-visible response, enhanced photocatalytic performance with optimum photodegradation of PW12/Ag-4/ZnO-6 for model dye (RhB ca. 99.93% at pH=6) and high reaction kinetics. Results show that the migration pathway of the charge carriers in this ternary system is significantly altered in counterparts of binary catalysts PW12/Ag and PW12/ZnO. The synergy catalysis interaction occurs between ·OH and ·O2− during the photodegradation process of PW12/Ag/ZnO composites. This work offers insights into the construction of efficient and stable all-solid-state Z-scheme heterostructures based on POMs.

Fabrication of g-C3N4/Ag/CoFe1.95Eu0.05O4 heterojunctions with enhanced photocatalytic degradation activity

We prepared g-C3N4/Ag/CoFe1.95Eu0.05O4 heterojunctions resulting in the effective visible-light absorption and promoted separation of photogenerated electron hole pairs. The kinetic constants of Z-type heterojunctions g-C3N4/Ag/CoFe1.95Eu0.05O4 for the degradation of methyl orange were 7.01 and 9.18 times higher than that of g-C3N4/Ag/CoFe1.95Eu0.05O4 and g-C3N4, respectively. Our work provides a new strategy to deal with the organic pollution by photocatalytic degradation.

Kagome-like BiP3 Monolayer: An Emerging Quasi-Direct Auxetic Semiconductor Coupled with High Anisotropic Mobility toward Visible-Light-Driven Photoelectrocatalytic pH-Robust Overall Water-Splitting.

Two-dimensional (2D) Janus materials exhibit an outstanding potential that can meet the rigorous requirements of photocatalytic water splitting resulting from their unique atomic arrangement. However, these materials are quite scarce. Through ab initio density functional theory calculations, we introduce a kagome topology into the honeycomb lattice of blue phosphorene using phosphorus and bismuth atoms to build a hybrid honeycomb-like kagome lattice, realized by a hitherto unknown kagome-like Janus-like BiP3 monolayer with robust stability. Excitingly, the out-of-plane asymmetry benefiting from kagome and honeycomb topologies gives rise to a significantly negative out-of-plane Poisson's ratio and an obvious built-in electric field pointing from the sublayer of the P atom to the sublayer of the Bi atom. In conjunction with the investigations that encompass semiconducting properties, such as a quasi-direct gap, suitable band-edge positions, effective visible-light absorption, and high carrier mobility, the BiP3 monolayer achieves overall water splitting at pH 0-14 regardless of strain. Moreover, this intrinsic electric field provides a sufficient photogenerated carrier driving force for water splitting. The bare BiP3 comprises P and Bi atoms that function as catalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) active sites, respectively. Upon exposure to light, the reaction of water into H2 and O2 can be observed across a pH range of 0-14. Meanwhile, by designing a transition-metal single-atom catalyst (TM@BiP3), our investigations have shown that embedding a single TM on BiP3 is a feasible route to improving the HER/OER activity by reducing the overpotentials to -0.039 and 0.58 eV for Mo and Os atoms, respectively. In this case, the positive value of the external potential acts as a sufficient OER driving force, i.e., in the light environment, the Os@BiP3 system can promote water molecules spontaneously oxidized into O2 at pH 0-14.

Fast and Excellent Enhanced Photocatalytic Degradation of Methylene Blue Using Silver-Doped Zinc Oxide Submicron Structures under Blue Laser Irradiation

In this study, laser-assisted chemical bath synthesis (LACBS) was used to prepare pure and Ag-doped ZnO submicron structures using a simplified hydrothermal approach that did not require a catalyst. The photocatalytic degradation of Methylene Blue was investigated under blue laser irradiation (λ = 444.5 nm and I = 8000 lx). The doping concentration varied (2%, 4%, 6%, 8%, tando 10%) and was prepared by LACBS using a continuous blue laser (P = 7 W, λ = 444.5 nm) for the first time. XRD, FE-SEM, EDX, and UV-Vis investigated the characteristics of the samples produced by the LACBS. ZnO: Ag(10%) submicron flowers are essential in rapid photodegradation under blue laser irradiation. The high surface area and catalytic activity of the prepared Ag-decorated ZnO are attributed to this improved photocatalytic activity. Using UV-visible spectroscopy, the photocatalytic efficiency was determined from the absorption spectra. The separation of photo-generated electron-hole pairs was facilitated, and the absorption edge of the hybrid submicron structures shifted into the visible spectrum region due to a combination of the Ag plasmonic effect and surface imperfections in ZnO. Effective visible light absorption was achieved via band-edge tuning, which increased the ZnO:Ag submicron structures’ ability to degrade dyes.

Ferrocene-sensitized titanium-oxo clusters with effective visible light absorption and excellent photoelectrochemical activity

Two novel ferrocene-sensitized titanium-oxo clusters were successfully synthesized, in which the ferrocene ligand acts as a photosensitizer for the photoelectric response.

Improvement ITO/WO3 photo anode electrode fabrication using electrodeposition technique for highly efficient photoelectrocatalytic insecticide degradation

The improvement of a semiconductor thin film preparation technique is considered to be the primary strategy for photoelectrocatalytic technique development. This research study's focus was to develop an electrodeposition technique for tungsten oxide (WO3) thin film fabrication to improve photoelectrocatalytic activities for water oxidation and insecticide degradation application. WO3 thin film deposition on conductive glass was developed using the electrochemical amperometric and cyclic voltammetric methods to optimize the essential parameters that affect the characteristics and photoelectrocatalytic properties of the fabricated WO3 electrode. Characteristics such as the visible light absorption, morphology, crystalline structure, and photoelectrocatalytic oxidation activities of the fabricated WO3 electrode were studied and compared with both electrodeposition methods. The fabricated WO3 electrode was found to improve photoelectrocatalytic water oxidation more with the amperometric method than with the cyclic voltammetric method and the traditional spin coating method, up to 4 times and 60 times, respectively. Photoelectrocatalytic enhancement is clarified by the effect of visible light absorption, roughness morphology, crystallinity, and charge transfer rate improvement. We can approve the efficacy of the developed WO3 electrode for insecticide removal under the photoelectrocatalytic mechanism. This is suitable for further scaling up the study for a wastewater treatment system application.

Facile Solvothermal Synthesis of Hollow BiOBr Submicrospheres with Enhanced Visible-Light-Responsive Photocatalytic Performance.

In this work, hierarchical hollow BiOBr submicrospheres (HBSMs) were successfully prepared via a facile yet efficient solvothermal strategy. Remarkable effects of solvents upon the crystallinities, morphologies, and microstructures of the BiOBr products were systematically investigated, which revealed that the glycerol/isopropanol volumetric ratio played a significant role in the formation of hollow architecture. Accordingly, the underlying formation mechanism of the hollow submicrospheres was tentatively put forward here. Furthermore, the photocatalytic activities of the resulting HBSMs were evaluated in detail with photocatalytic degradation of the organic methyl orange under visible light irradiation. Encouragingly, the as-obtained HBSMs with striking recyclability demonstrated excellent visible-light-responsive photocatalytic performance, which benefits from their large surface area, effective visible light absorption, and unique hollow feature, highlighting their promising commercial application in waste water treatment.

Direct Z-scheme FeVO4/BiOCl heterojunction as a highly efficient visible-light-driven photocatalyst for photocatalytic dye degradation and Cr(VI) reduction

In this work, potential applications of a direct Z-scheme FeVO4/BiOCl heterojunction for photocatalytic degradation of organic dyes (methylene blue, MB and rhodamine B, RhB) and reduction of hexavalent chromium (Cr(VI)) ion under visible light irradiation were reported. Firstly, FeVO4 and BiOCl were synthesized by using a microwave heating method. Then, the FeVO4/BiOCl nanocomposites with different weight percentages of FeVO4 (1, 3, 6.25, 12.5 and 25%wt) were fabricated by a method of modified wet impregnation. The photocatalytic degradation activities of the nanocomposites were investigated in parallel with pure BiOCl and FeVO4. Among the as-prepared nanocomposites, the FeVO4/BiOCl nanocomposite with 6.25%wt of FeVO4 exhibited the highest photocatalytic dye degradation efficiency; 99.8% of RhB was degraded after being irradiated for 360 min, while 87.2% of MB was degraded. Similarly, this nanocomposite photocatalytically reduced 97.8% of Cr(VI) at a pH value of 3. The superior photocatalytic activity can be ascribed to the effective visible light absorption of the FeVO4/BiOCl heterojunction and the suppression of the recombination process of photogenerated electron–hole pairs. Additionally, the improved charge migration and separation efficiencies between FeVO4 and BiOCl through the direct Z-scheme charge transfer pathway are involved, as evidenced by the trapping experiments, and the UV–visible diffuse reflectance (UV–vis DRS), photoluminescence spectroscopy (PL) and electrochemical impedance spectroscopy analyses. Photocatalytic mechanisms of the direct Z-scheme FeVO4/BiOCl heterojunction for the photodegradation of RhB and photoreduction of Cr(VI) have been proposed and discussed in greater detail.

Conductive Black Titania Nanomaterials for Efficient Photocatalytic Degradation of Organic Pollutants

Titanium dioxide (TiO2) as an important semiconductor is widely used in the fields of solar cell, solar thermal collectors, and photocatalysis, but the visible-light power harvest remains insufficient due to the little effective visible-light absorption and many carrier-recombination centers originating from the wide band gap structure. Herein, conductive black titania (BT) nanomaterials with crystalline-TiO2-core/amorphous-TiO2−x-shell structure prepared through two-zone Al-reduction route are found efficient in photocatalyzing the degradation of organic pollutants to environmentally friendly products under full solar and even visible light irradiation. The unique core–shell structure and numerous surface oxygen vacancies or Ti3+ species in the amorphous layer accompanying prominent physicochemical properties of narrow band gap, high carrier concentration, high electron mobility, and excellent separation and transportation of photoinduced e−−h+ pairs result in exceptional photocatalytic efficiency. The optimized BT-500 (pristine TiO2 treated at 500 °C during two-zone Al-reduction process) catalyst achieves superior photocatalytic degradation rates for toluene and ethyl acetate as well as an excellent photostability with high degradation efficiency of 93% for the 6th reuse.Graphic

A Photoelectrochemical Biosensor Fabricated using Hierarchically Structured Gold Nanoparticle and MoS2 on Tannic Acid Templated Mesoporous TiO2

AbstractIn a tannic acid assisted synthesis of mesoporous TiO2, tannic acid was used as a cost effective and non‐toxic template for pore formation. Meanwhile, a gold nanoparticles (Au NPs) deposited TiO2 nanocomposite was coated on an indium tin oxide electrode for the fabrication of a photoelectrochemical (PEC) biosensing system. Upon the formation of anatase structure, the electrode was coated with MoS2 for effective visible light absorption. The mesoporous structure led to an enhanced surface area by improving Au NPs and glucose oxidase adsorption. Incorporation of Au NPs led to an enhanced photonic efficiency due to the generation of Schottky barriers. The obtained nanocomposite was used for the light‐driven, real‐time, and selective PEC glucose sensing. Under visible light irradiation, the enzyme immobilized electrodes yielded significant photocurrent improvement owing to the releasing electron donor H2O2. The obtained PEC biosensor demonstrated acceptable reproducibility and stability with a sensitivity of 4.42 μA mM−1 cm−2 and a low detection limit of 1.2 μM glucose. Also, the linear measurement range was found to be 0.004–1.75 mM glucose. The results indicated that the proposed production method of mesoporous TiO2 will pave the way for a green chemistry based porous material production, along with the extension of the implementation of semiconductors in PEC biosensing systems.

The effect of silver oxidation on the photocatalytic activity of Ag/ZnO hybrid plasmonic/metal-oxide nanostructures under visible light and in the dark

A new synergetic hybrid Ag/ZnO nanostructure was fabricated which is able to cause photocatalytic degradation (in high yields) of methylene blue under visible light as well as in the dark. In this nanostructure, ZnO was synthesized using the arc discharge method in water and was coupled with Ag via a chemical reduction method. X-ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy results confirmed the existence of defects in ZnO in the hybrid nanostructures; these defects act as electron traps and inhibit the recombination of electron-hole pairs. The absorption edge of the hybrid nanostructure shifts toward the visible region of the spectrum due to a combination of the Ag plasmonic effect and the defects in ZnO. Band-edge tuning causes effective visible light absorption and enhances the dye degradation efficiency of Ag/ZnO nanostructures. Silver oxidation in the hetero-structure changed the metal-semiconductor interface and suppressed the plasmonic enhancement. Nevertheless, the synthesized Ag/ZnO decomposed methylene blue in visible light, and the silver oxidation only affected the catalytic activity in the dark. This work provides insight into the design of a new and durable plasmonic-metal oxide nanocomposite with efficient dye degradation even without light illumination.

Ternary CdS-MoS2 coated ZnO nanobrush photoelectrode for one-dimensional acceleration of charge separation upon visible light illumination

Ternary CdS-MoS2 coated ZnO nanobrush photoelectrode from chemical bath deposition was successfully fabricated on a FTO substrate for photocatalytic degradation of amoxicillin. The vertically grown ZnO core on FTO substrates provided a direct pathway for electron transfer; while the well-crystallized CdS/MoS2 shell offered effective visible light absorption and increased active sites. Prolonged lifetime of charge carriers was demonstrated by transient photovoltage (TPV) measurement. The ternary brush-type electrode exhibited enhanced photoelectrochemical performance with a photocurrent density of 20.32 mA/cm2 at 0 V vs. Ag/AgCl under visible light illumination (λ ≧ 420 nm), which was 5.2 times, 1.8 times and 3.6 times of that of pristine CdS, CdS-MoS2 film and ZnO/CdS nanobrush, respectively. The improved photoelectrochemical activity was ascribed to the enhancement of light absorption, appropriate band alignment and prolonged charge carriers’ lifetime. The ZnO/CdS-MoS2 nanobrush film degraded 94% of amoxicillin in 60 min, exhibiting promising photocatalytic activity under visible light illumination (λ ≧ 420 nm). The reusability and stability of the electrode were evaluated by recycling experiments. The intermediates of amoxicillin oxidation were also identified and the degradation pathway was proposed.

Arithmetic and experimental approach to effect of visible light absorption on silicone plate in high-power LED module

In a light emitting diodes (LEDs), the effect of visible light absorption on silicone encapsulant temperature has largely been overlooked by the scientific community. In this paper, we develop a new optical energy model to calculate the absorption power of a silicone plate in a remote phosphor LED module. In addition, we introduce a unique experiment for visible light absorption. Three types of silicone plate are investigated – a transparent silicone plate in a blue LED and two phosphor-mixed silicone plates (YAG:Ge, yellow phosphor) in white LEDs. We discover that by mixing phosphor with transparent silicone, the absorption coefficient is increased to 2.5 times in the case of 3 wt% phosphor-mixed silicone, and 5.9 times in the case of 30 wt% phosphor-mixed silicone compare with transparent silicone plate. Moreover, we find that visible light absorption only is able to increase silicone plate temperature by 7.3 °C in the case of transparent silicone, 18.7 °C in the case of 3 wt% phosphor-mixed silicone, and 43.3 °C in the case of 30 wt% phosphor-mixed silicone.

Preparation of bismuth stannate/silver@silver chloride film samples with enhanced photocatalytic performance and self-cleaning ability

We report a novel technique to fabricate bismuth stannate/silver@silver chloride (Bi2Sn2O7/Ag@AgCl) films on conventional glass substrates. The film exhibited a remarkable self-cleaning capability against organic dyes under visible light. Porous Bi2Sn2O7 (BSO) film was first sintered on a glass substrate, followed by implantation of AgCl in it and photo-induction to produce Ag@AgCl. The degradation of organic dyes and photoelectrochemical studies indicate that, compared with BSO film, Bi2Sn2O7/Ag@AgCl film had a much improved photocatalytic ability, probably due to the enhanced electron transfer efficiency and synergistic effect of visible light absorption of the two semiconductors. The possible mechanism of this marked improvement was investigated and interpreted in terms of electrons and holes separation efficiency and charge circulation routes at the interfaces within the Bi2Sn2O7/Ag@AgCl composite film. The film provided in this study may well have practical applications due to its simplicity of preparation, excellent photocatalytic ability and reasonable stability.

Theoretically Manipulating Quantum Dots on Two-Dimensional TiO2 Monolayer for Effective Visible Light Absorption.

Low solar energy harvesting and conversion efficiency has become a major problem in solar energy science and engineering owing to the difficulty in capturing solar energy across the wide solar spectrum, especially in the visible light range. Inspired by the extraordinary properties of materials arising from decreased dimensions, in this study, we explore a nanocontact system formed by a two-dimensional (2D) TiO2 monolayer and II-VI semiconductor (CdX)13 (X = S, Se, and Te) nanocages for engineering the visible light absorption. The nanocontact system, via either Ti-X or Cd-O bond coupling mechanism, forms an ideal type II band alignment, where the stronger donor-acceptor coupling in the Ti-X contact system more efficiently relaxes the coupled geometry and helps it to couple to more electrons, therefore leading to an enhancement of the absorption peaks in the visible frequency range. On changing the element X in (CdX)13 from S to Se then Te, a red shift of the visible light absorption peaks accompanied by stimulating optical response of the whole nanocontact system was observed. Nanocontacting semiconductors comprising low-dimensional (CdX)13 nanocage@TiO2 monolayer systems, which promote charge separation and optical absorption in the visible range that arise from the effects of adsorbent nature, decreasing size, and efficient interfacial coupling mechanism, are therefore promising photovoltaic and photocatalytic materials.

Synthesis and optical properties of TDQD and effective CO 2 reduction using a TDQD-photosensitized TiO 2 film

Abstract In an attempt to find a suitable visible light absorber, a TDQD[(E)-3-(5-(4-(5-(4-(bis(4-(hexyloxy)phenyl)amino)phenyl)thiophen-2-yl)-6,7-diethyl-[1,2,5]thiadiazolo[3,4-g]quinoxalin-9-yl)thiophen-2-yl)-2-cyanoacrylic acid] dye is synthesized and introduced onto the surfaces of commercialized TiO2 (P-25) particles as a photosensitizer to improve their photo-absorption in the visible range. The photocatalytic performance of the TDQD-photosensitized-TiO2 is superior to that of the non-photosensitized TiO2 nanomaterial: the photoreduction of CO2 to CH4 is remarkably improved on the former with the production of 1290 μmol gcat−1 L−1 of CH4 after 8 h of reaction. These results are attributed to the effective visible light absorption and charge separation, and the inhibited recombination of the photogenerated electron–hole pairs on the TDQD-photosensitized-TiO2. Finally, the prepared TDQD and TDQD-photosensitized-TiO2 powders were characterized through cyclic voltammetry (CV), ultraviolet-visible (UV–vis) and FT-IR spectroscopies and photocurrent density analysis.

Self-assembled Bi2MoO6/TiO2 nanofiber heterojunction film with enhanced photocatalytic activities

TiO2 nanofiber film (TiO2 NFF) was successfully fabricated by an ethylene glycol-assisted hydrothermal method, and then self-assembled flake-like Bi2MoO6 was grown on the surface of TiO2 nanofiber under alcohol thermal condition. The investigations indicate that the nanofiber structure of TiO2 films exhibits excellent visible light scattering property, the scattering light overlaps with the absorption band of Bi2MoO6, which can enhance the utility of incident light. The prepared Bi2MoO6/TiO2 composites show obviously enhanced photocatalytic activity for methylene blue (MB) degradation compared with pure TiO2 nanofiber under visible light irradiation (λ>420nm). The enhanced photocatalytic activity is primarily attributed to the synergistic effect of visible light absorption and effective electron-hole separation at the interfaces of the two semiconductors, which is confirmed by photoluminescence (PL) and electrochemical tests.

Efficient visible light photocatalytic oxidation of NO with hierarchical nanostructured 3D flower-like BiOClxBr1−x solid solutions

Bismuth oxyhalides (BiOX, X = Cl, Br, I) as effective photocatalysts have attracted a wide attention for its outstanding performance on air purification with solar energy. In this work, a series of band-gap engineered BiOClxBr1−x homogeneous solid solution materials were explored as efficient visible-light induced photocatalysts. The BiOClxBr1−x solid solution photocatalysts with 3D hierarchical nanostructures have been successfully synthesized through a facile temple free hydrothermal method. The prepared BiOClxBr1−x possess a single tetragonal crystal structure without any secondary phases in spite of x varying from 0 to 1 indicating a homogeneous solid-solution characteristic. However, the band gaps of BiOClxBr1−x solid solutions are modulated from 3.30 to 2.75 eV by decreasing x from 1 to 0, which extends the light absorption from 375 nm to 450 nm. The obtained BiOCl0.5Br0.5 sample displays enhanced photocatalytic activity for the oxidation of NO, with a good stability under visible light. The existence of hydroxyl radicals and super oxygen radicals confirm its photocatalytic activities. The highly enhanced visible light photocatalytic activity of BiOCl0.5Br0.5 can be ascribed to the large specific surface area, hierarchical structures and the modified band structures. Furthermore, the modified band-gap adapts the balance between adequate redox potentials and effective visible light absorption. The present work provides novel insights into the design and synthesis of 3D hierarchical nanostructures with band-gap engineering to explore novel photocatalysts.

ChemInform Abstract: Photocatalysis by 3,6‐Disubstituted‐s‐tetrazine: Visible‐Light Driven Metal‐Free Green Synthesis of 2‐Substituted Benzimidazole and Benzothiazole.

Abstract3,6‐Di(pyridin‐2‐yl)‐1,2,4,5‐tetrazine exhibits effective visible light absorption and reversible one‐electron reduction behavior.

Synthesis and visible light photocatalytic activity of β-AgVO3 nanowires

β-AgVO3 nanowires are synthesized by the hydrothermal method. The synthesis yields nanowires with a monoclinic phase structure. Typical nanowires have diameter of about 200–700 nm and length up to 300 μm. Photocatalytic degradation of Rhodamine B dye is investigated. It is found that the β-AgVO3 nanowires possess excellent catalytic degradation activity owing to its effective visible light absorption and well crystallization. The highly photocatalytic activity suggest its possible application in the organic pollutant treatment under visible light irradiation.