Excellent Visible-light Photocatalytic Activity Research Articles

Plasmonic Au-MoS2 Nanohybrids Using Pulsed Laser-Induced Photolysis Synthesis for Enhanced Visible-Light Photocatalytic Dye Degradation.

The Au-MoS2 nanocomposites (NCPs) exhibit excellent visible-light photocatalytic activity and potential applications in the photocatalytic degradation of organic dyes. In this study, an Au-MoS2 heterojunction structure with Au nanoparticles (NPs) deposited on MoS2 nanosheets was synthesized via the pulsed laser-induced photolysis method. The influence of Au content on the photocatalytic performance was systematically investigated, and the working mechanism under visible light excitation was elucidated. The optimal Au-MoS2 NCPs exhibited efficient degradation of methylene blue (MB) dye, mainly attributed to the plasmon resonance effect of Au NPs which facilitated the visible light harvesting and hot electron injection. The Au/MoS2 interface promoted the separation and transfer of photogenerated charge carriers. The electrostatic adsorption between positively charged MB molecules and the negatively charged MoS2 surface favored the affinity toward active sites. Furthermore, the photogenerated electrons and holes participated in generating reactive oxygen species such as superoxide and hydroxyl radicals, which initiated the oxidative degradation of MB. The PLIP-introduced Au NPs not only endowed the material with excellent visible light responsivity but also possibly modulated the electronic structure and photocatalytic active sites of MoS2 through an intrinsic effect, providing new insights for further enhancing the photocatalytic performance of Au-MoS2 NCPs.

Preparation of core-shell like Bi2WO6/BiOCl heterojunction with excellent visible light photocatalytic activity

Constructing a ‘Z-scheme’ heterojunction is an effective method for improving photocatalyst activity. Core-shell like Z-scheme Bi2WO6/BiOCl heterojunction was synthesized through a two-step method. The arbutus-like BiOCl microsphere core was first gained by a solvothermal method. Then the Bi2WO6 nanosheet shell was in situ on the surface of the BiOCl microsphere through another solvothermal process. The Bi2WO6/BiOCl heterojunction had a much better photocatalytic performance than that of the single Bi2WO6, which was owing to the enlarged BET surface area, enhanced light absorption, and photocarriers migration. The photocatalytic mechanism of the Bi2WO6/BiOCl heterojunction was also proposed.

Rare earth induced lattice distortion of Bi2WO6 to effectively improve photocatalytic performance: Experimental and DFT calculations

The excellent visible light photocatalytic activity of bismuth-based photocatalysts has attracted the interest of many scholars at home and abroad. In this paper, rare earth (Sm, La, Ce, Eu) doped Bi2WO6 photocatalysts were prepared by a one-step hydrothermal method using bismuth nitrate and sodium tungstate as precursors. The microstructures and spectroscopic performances of prepared materials were investigated utilizing characterization methods, such as XRD, XPS, UV–vis, TEM, and N2 adsorption-desorption, etc., and the effluent removal performances were studied by using rhodamine B as a simulated degradation dye and the photodegradation mechanism was investigated in combination with DFT calculations. XRD indicates that the rare earth doping leads to the lattice distortion of the (131) crystal surface of Bi2WO6, and the relative amount of distortion is directly proportional to the photocatalytic activity; UV–vis spectra show that the absorption edge of Bi2WO6 is obviously red-shifted with the rare earth doping, and N2 adsorption-desorption curve show that the doped rare earths make the specific surface area of the sample effectively increased. Moreover, XPS spectrum suggests that the doped rare earth Ce and Eu often exist in the form of metastable oxidation states, and the transformation between Ce3+/Ce4+ and Eu2+/Eu3+ oxidation states is easy to form impurity energy levels between Bi2WO6, which make the energy level significantly enriched to broaden the absorption range and reduce band gap width of the material. DFT calculations further indicate that the rare earths successfully replace Bi sites. One of the main reasons for the improvement of photocatalytic activity is that rare earth doping is easier to replace Bi sites, leading to increased relative aberration; another one is that the arrangement of EVB and ECB in the photocatalytic mechanism is type-II, which contributes to red-shift of absorption edge and effective separation of electron-hole pairs in the photocatalytic process, thus improving the photocatalytic activity.

Insight into mechanism of excellent visible-light photocatalytic activity of CuO/MgO/ZnO nanocomposite for advanced solution of environmental remediation

Environmental remediation has sought several innovative ways for the treatment of wastewater and captivated researchers around the globe towards it. Through this study, we aim to proceed with the efforts to foster sustainable and feasible ways for the treatment of wastewater. In this work, we report the sol-gel synthesis of CuO/MgO/ZnO nanocomposite and carry out their systematic characterization with the help of state-of-the-art analytical techniques, such as FTIR, SEM, TEM, PL, XRD, Raman, and AFM. The SEM along with TEM and AFM provided useful insights into the surface morphology of the synthesized nanocomposite on both 2D and 3D surfaces and concluded the well-dispersed behavior of the nanocomposite. The characteristic functional groups responsible for carrying out the reaction of Cu–O, Mg–O, and Zn–O were identified by FTIR spectroscopy. On the other hand, crystal size, dislocation density, and microstrain of the nanocomposite were calculated by XRD. For optical studies, photoluminescence spectroscopy was performed. Once the characterization of the nanocomposite was done, they were eventually treated against the toxic organic dye, methylene blue. The calculated rate constant values of k for CuO was 2.48 × 10−3 min−1, for CuO/MgO (2.04 × 10−3 min−1), for CuO/ZnO (1.82 × 10−3 min−1) and CuO/MgO/ZnO was found to be 2.00 × 10−3 min−1. It has become increasingly evident that nanotechnology can be used in various facets of modern life, and its implementation in wastewater treatment has recently received much attention.

Effect of annealing temperature on the formation of oxygen vacancies on the surface of flower-like SnSe/SnO2 heterostructure and visible light catalytic performance

The morphology, structure, and oxygen vacancies in principle determine the light absorption, charge transfer, and separation of photocatalysts, thereby determining their photocatalytic performance. In this study, flower-like SnSe obtained from hydrothermal reactions was oxidized to obtain heterojunctions with SnSe/SnO2. Flower-like SnSe/SnO2 heterojunctions with different concentrations of oxygen vacancies were prepared by annealing them in an argon atmosphere at different temperatures. The flower-like SnSe/SnO2 series with different oxygen vacancies were systematically characterized by TEM, XRD, XPS, PL, and EPR. The research results demonstrate the presence of oxygen vacancies in the flower-like SnSe/SnO2. As the annealing temperature increases, the surface oxygen vacancy concentration shows a trend of first increasing and then decreasing. When the annealing temperature reaches 600 °C, the oxygen vacancy concentration of flower-like SnSe/SnO2 is the highest. Meanwhile, research has shown that surface oxygen vacancies help expand the light absorption range, and the increased valence bandwidth leads to effective charge transfer and separation, thereby promoting visible light photoactivity. SnSe/SnO2-600 °C exhibited excellent visible light photocatalytic activity. The photodegradation of methylene blue (MB) at ≥ 400 nm can reach ∼70% within 120 min. This study verified the route for the introduction of oxygen vacancies via facile calcination and constructed SnSe/SnO2 with surface oxygen vacancies, providing a reference with deep insights for improving photocatalytic activity.

In situ synthesis of core-shell like BiVO4/BiOCl heterojunction with excellent visible-light photocatalytic activity

A well-integrated core-shell like BiVO4/BiOCl heterojunction was synthesized by a two-step solvothermal method. BiVO4 nanosheets shell were in situ synthesized on the surface of BiOCl microsphere core. Compared with the pure BiOCl, it had a larger BET surface area, stronger visible-light absorption and faster transfer of photocarriers. It had a much better photocatalytic performance than the pure BiVO4, which was owing to the enlarged surface area, enhanced visible-light absorption and photocarriers’ separation and transfer. The photogenerated electrons and holes of the BiVO4/BiOCl heterojunction transferred through a Z-scheme route, which made it had a better photocatalytic performance than that of the II type one.

Insight into the mechanism of excellent visible-light photocatalytic activity of TiO2/graphene nanocomposite for photodegradation of organic pollutants in water

Insight into the mechanism of excellent visible-light photocatalytic activity of TiO2/graphene nanocomposite for photodegradation of organic pollutants in water

Construction of novel fluorescent synergistic photocatalytic double Z-scheme photocatalyst for efficient antifouling of polydimethylsiloxane coatings

It has been challenging to enhance the static antifouling (AF) performance of silicone AF coatings using low-cost, high-performance, and environmentally friendly materials. In this work, a graphite-phase carbon nitride/titanium dioxide nanotubes/Sr2MgSi2O7:(Eu2+, Dy3+) long afterglow powder (g-C3N4/TNTs/SLAP, CTS) ternary double Z-scheme heterostructure photocatalyst was designed based on the application of photocatalytic technology in the field of AF and environmental remediation and the function of fluorescent corals and Watasenia scintillans emitting fluorescence to prevent the adhesion of fouling organisms. Then, this composite photocatalyst was dispersed in polydimethylsiloxane resin (PDMS) to prepare g-C3N4/TNTs/SLAP/PDMS (P-CTS) biomimetic fluorescent synergistic photocatalytic AF coating. The double Z-scheme heterostructure formed between the CTS enhances the carrier separation and transport efficiency, thus conferring excellent visible light photocatalytic activity on the CTS. At the same time, the fluorescence emitted by SLAP as a “light store” at night not only prolongs the photocatalytic activity but also inhibits the adhesion of fouling organisms. The results showed that the minimum attachment rates of S. aureus, E. coli, and benthic diatoms of P-CTS were 1.65 %, 1.40 %, and 10.20 %, respectively, under simulated natural diurnal conditions. This novel biomimetic fluorescent synergistic photocatalytic AF coating has good potential applications in marine AF and environmental remediation.

A novel combustion drying synthesis route of 3D WO3–SiO2 composite aerogels for enhanced adsorption and visible light photocatalytic activity

The 3D network nanoporous WO3–SiO2 composite aerogels were successfully synthesized by a novel combustion drying method. All the as-prepared composite aerogels were still with a typical three-dimensional network nanoporous structure, and exhibited high specific surface area with 486–667 m2/g and pore volume 2.0–2.68 cm3/g. Although samples were prepared by burning process, they still shown good hydrophobicity and heat resistance. The adsorption and photocatalytic properties of WO3–SiO2 composite aerogels showed that WO3–SiO2 composite aerogels realized the comprehensive utilization of the adsorption and photocatalysis, and the composite aerogels with high W content exhibited excellent adsorption performance and visible light photocatalytic activity. At last, the mechanism of synthesis of WO3–SiO2 composite aerogels by combustion drying technology was discussed. The results provide a new technical solution for the synthesis of composite aerogels photocatalysts.

Construction of a 2D layered BiVO4/zinc porphyrin (ZnTCPP) S-scheme heterostructure boosting photocatalytic N2oxidation performance

The unique S-scheme heterojunction of a 2D/2D BiVO4/metalloporphyrin (ZnTCPP) layered composite showed excellent visible-light photocatalytic N2oxidation activity.

A fast and moderate solvothermal method for Bi60In2O93 microspheres: Synthesis, characterization and photocatalytic properties

A visible-light response Bi60In2O93 microsphere was synthesized via a facile solvothermal reaction for photocataytic degradation of organic pollutants. Bi60In2O93 displays an excellent visible-light photocatalytic activity. Experimental results reveal that the morphology of Bi60In2O93 microspheres is largely dependent on the reaction condition of the amount of In(NO3)3·4.5H2O and temperature. The photocatalytic activity of Bi60In2O93 was probed by the degradation efficiency of tetracycline. The degradation efficiency of tetracycline reaches 82.1 % within 1 h under the visible-light irradiation with the assistance of Bi60In2O93. The remarkable photocatalytic performance on Bi60In2O93 microsphere was attributed to efficient electron-hole separation. The reactive species trapping experiment results indicated that the h+ and •O2– are the major active species of the degradation of tetracycline.

Green and reusable Ag/AgCl-TiO2 nanocomposites for visible light-triggered dye degradation

• Ag/AgCl-TiO 2 nanocomposites are synthesized in a green, single-step process. • Satureja khuzistanica extract acts as a reducing agent and nanocomposite stabilizer. • More than 99% methyl orange is degraded under visible light irradiation. • High-efficiency TiO 2 -based photocatalysts developed for engineering and environmental applications. Ag/AgCl-TiO 2 plasmonic nanocomposites (NCs) are endowed with excellent visible-light photocatalytic activity. However, only a few studies investigated environmentally friendly approaches to their synthesis. In this work, Ag/AgCl-TiO 2 NCs at five different compositions were prepared in a single-step process by a green and cost-effective route, using Satureja khuzistanica Jamzad aqueous extract. The role of the aqueous plant extract as a reducing and stabilizing agent, and the formation of the NCs were evidenced by several techniques, including FT-IR, EDS, SEM, HRTEM, elemental mapping, and XRD. The morphological analysis demonstrated that the NCs formed nanoaggregates with an average size of 30 nm. The synthesized Ag/AgCl-TiO 2 NCs displayed a remarkable photoactivity in the visible light region, as confirmed by the significantly higher degradation rates of methyl orange (MO) compared to TiO 2 . In particular, the 15% Ag/TiO 2 molar ratio sample revealed a MO degradation efficiency higher than 99% under visible light, and retained high photocatalytic activity even after several degradations runs. Overall, the green, cost-effective, and scalable synthesis of Ag/AgCl-TiO 2 NCs herein reported provides a novel, more sustainable strategy for the high-efficiency modification of TiO 2 photocatalyst in engineering and other environmental applications.

Coral-like ZnO/BiOBr Z-scheme heterojunction with excellent visible-light photocatalytic activity

Coral-like ZnO/BiOBr Z-scheme heterojunction with excellent visible-light photocatalytic activity

Enhanced H2 evolution performance by carbonized SiC/g-C3N4 heterojunction under visible-light illumination

In this study, carbonized silicon carbide/graphitic carbon nitride ((SiC/C)/g-C3N4) composites were fabricated via a facile calcination method. The optimal SiC/C/g-C3N4 composite shows an excellent visible-light photocatalytic activity for water splitting, with the highest hydrogen evolution amount being 200.2 μmol, which is four times higher than that of pure g-C3N4 when triethanolamine and platinum (1.0 wt%) are used as the sacrificial agent and cocatalyst, respectively. With an intimate interface between SiC/C and g-C3N4, the energy band structure of g-C3N4 was well engineered for photocatalytic H2 production. This study provides a novel method for fabricating g-C3N4-based heterojunctions for application in environmental conservation.

Constructing visible-light-driven self-cleaning UF membrane by quaternary ammonium-functionalized Ti-MOFs for water remediation

In this study, quaternary ammonium-functionalized MIL-125 (Me 3 N + -MIL-125) decorated polyvinylidene fluoride (PVDF) ultrafiltration (UF) membrane was fabricated by a facile two-step assembly method to remove rhodamine B (RhB, a model dye). For comparison purpose, MIL-125 and amino-functionalized MIL-125 (NH 2 -MIL-125) based membranes were also prepared. Porous Ti-MOFs layer was firmly anchored on membrane surface by crosslinking reaction between polyethyleneimine and epichlorohydrin, which caused higher hydrophilicity, more positive charge and efficient thermal stability of membrane. Compared to MIL-125 and NH 2 -MIL-125, Me 3 N + -MIL-125 endows the membrane with superior water flux (192.7 L m −2 h −1 , transmembrane pressure = 0.2 MPa), RhB rejection ratio (60.4%) and antibacterial efficiency against E. coli (99.98%) and S. aureus (99.95%). In addition, Me 3 N + -MIL-125 decorated membrane exhibits excellent visible-light photocatalytic activity. Membrane performance can be fully recovered by visible light irradiation due to the oxidation degradation by reactive oxygen species (ROS, •OH and O 2 •- ) that generated on Me 3 N + -MIL-125 with the wider visible-light response range and narrower bandgap energy (1.65 eV). This novel multifunctional UF membrane is promising in the application of dye-contaminated water remediation. • A novel visible-light photocatalytic UF membrane was fabricated by a facile method. • Me 3 N + -MIL-125(Ti) imparts membrane with superior performance than NH 2 -MIL-125(Ti). • The stable water flux and RhB removal are 192.7 L m −2 h −1 and 60.4%, respectively. • The membrane shows excellent anti-fouling, self-cleaning and antibacterial ability.

Excellent visible-light photocatalytic activity towards the degradation of tetracycline antibiotic and electrochemical sensing of hydrazine by SnO2–CdS nanostructures

The present study investigated a tin oxide/cadmium sulfide (SnO2–CdS) nanostructure for enhancing the photocatalytic efficiency of CdS nanoparticles. Herein, the desired nanostructure was fabricated through a straightforward and cost-effective approach. The physicochemical properties of the fabricated nanostructure were analyzed by various characterization techniques. The SnO2–CdS shows an excellent band-gap of 2.14 eV, a high surface area of 29 m2/g, and favorable photoluminescence properties. The examination of the degradation capabilities of SnO2–CdS nanostructures (SOCdS) with visible light was conducted using tetracycline hydrochloride (TC), methylene blue (MB), and Congo red (CR) as models of antibiotic and dye pollutants. The photocatalyst possessed a TC removal efficiency of 94.5 ± 0.02% in 60 minutes under visible-light irradiation with over 60 ± 0.06% adsorption of TC under equilibrium conditions. Further, the photocatalysts exhibited excellent performance for MB and CR degradation with degradation effectiveness of 99.08 ± 0.01% in 120 min and 83 ± 0.06% in 40 min, respectively. In addition, the glassy carbon electrode (GCE) was modified with SOCdS (SOCdS/GCE) and was employed for the efficient and precise detection of hydrazine at room temperature. The SOCdS/GCE showed first-rate response for the recognition of hydrazine: CV: LOD of 0.18 μM, 8 μM–50 μM linear range, and 25.7 μA μM−1 cm−2 of sensitivity; and LSV: LOD of 0.19 μM, 5 μM–50 μM linear range, and 23.6 μA μM−1 cm−2 of sensitivity. Results suggest that the SnO2–CdS nanostructure showed excellent photocatalytic activity than bare-CdS NPs and has the ability to detect the analyte viz. hydrazine. The role of CdS nanoparticles is interesting to enhance the photocatalytic and electrochemical properties. We report a straightforward and cost-effective fabrication approach for SnO2–CdS nanostructure and provide a robust platform for the utilization of chalcogenides-based systems for environmental remediation and detection of hazardous chemicals.

Graphene aerogel-based NiAl-LDH/g-C3N4 with ultratight sheet-sheet heterojunction for excellent visible-light photocatalytic activity of CO2 reduction

NiAl-LDH (NALDH) nanosheets were in intimate contact with g-C3N4 (CN) nanosheets to form ultratight sheet-sheet heterojunctions, which interweaved into network framework with introduction of the graphene aerogel (GA). Notably, the NALDH/CN/GA-20 showed a remarkable CO production rate of 28.83 μmol·g−1·h−1 under visible light irradiation, which was 24 and 16 times those of pure NALDH and bare CN, respectively. Furthermore, it was far exceeding the reported conventional CO2 photocatalytic reduction efficiency. The ultratight sheet-sheet heterojunctions not only shorten the charge transmission distance, but result abundant active sites and coupling large interfaces. The unique structure promoted the transport and separation of photogenerated carriers, and facilitated effective mass transport and light absorption. Multi electron series reduction mechanism based on type-II photocatalytic system was proposed to explain the CO2 reduction pathway. This work provides insight for designing photocatalysts with ideal performance for CO2 reduction.

Heterogeneous In/Mo cooperative bandgap engineering for promoting visible-light-driven CO2 photoreduction

The Mo-modified InOOH/In(OH)3 heterojunction photocatalyst with excellent visible-light photocatalytic activity was achieved due to its high-efficiency photogenerated charge separation and transfer efficiency.

Bamboo-charcoal-loaded graphitic carbon nitride for photocatalytic hydrogen evolution

Crystalline graphitic carbon nitride is an excellent photocatalyst for hydrogen production due to its non-toxicity, stability, elemental abundance, and visible-light response. Herein, we present a new type of composite photocatalysts, eco-friendly bamboo-charcoal-loaded graphitic carbon nitrides to accelerate the separation of electron-hole pairs. The suitable loading of bamboo charcoal on graphitic carbon nitrides shows an increased specific surface area from 85 to 120 m2 g−1, and excellent visible-light photocatalytic hydrogen production activity of 4.1 mmol g−1 h−1, which is 2.3 times higher than that of pristine carbon nitride (1.8 mmol g−1 h−1). Under irradiation, the photogenerated electrons fast migrate from graphitic carbon nitride to bamboo charcoal through an ohmic contact between them, reducing the recombination of electron-hole pairs. This study highlights the effect of carbonaceous material loading on photocatalytic activity of carbon nitrides and opens an avenue to design efficient loaded photocatalysts with natural abundant materials.

An efficient and unique route for the fabrication of highly condensed oxygen-doped carbon nitride for the photodegradation of synchronous pollutants and H2O2 production under ambient conditions

N2-assisted thermal polycondensation of a novel supramolecular self-assembly based on melamine, cyanuric acid, and thiourea produced S-doped carbon nitride. Molecular dynamics simulation estimated nonbonding energies between the melamine-cyanuric acid adduct and thiourea. The C–S functional group was efficiently converted to C–O by facile calcination in a static air atmosphere, which gave a highly condensed O-doped carbon nitride nanosheet (O-CN). Density functional theory (DFT) calculations and experimental results confirmed that the oxygen-doped site is more stable and provides midgap states near the conduction band position of CN compared with sulfur doping. O-CN exhibited excellent visible light harvesting and photocatalytic activities toward removal of tetracycline and rhodamine B in an initial 15 min while producing a highly stable amount of H2O2 under an open atmosphere without a sacrificial agent. These outstanding performances result from synergistic approaches that lead to the modified polycondensation process, unprecedented reduction ability, and enhanced optical properties.