Excellent Photocatalytic Efficiency Research Articles

Microwave-assisted synthesis of NiTe2 photocatalyst as a facile and scalable approach for energy-efficient photocatalysis and detoxification of harmful organic dyes

Microwave-assisted synthesis of NiTe2, a metal dichalcogenide, is reported here as a facile and rapid preparation method for energy-efficient and scalable photocatalysis application and detoxification of water pollution. Synthetic dyes as organic pollutants in water, such as Methylene blue, Congo red, and Methyl orange cause serious health and environmental issues, which are degraded effectively by heterogeneous photocatalysis using NiTe2 as a catalyst. The photons from a UV-source generates excitons within the surface of NiTe2 that can react with O2, H2O, and hydrogen peroxide (H2O2) initiator to convert them into reactive superoxide anions (−O2), hydroperoxyl (HOO), and hydroxide radicals (OH) which holds strong oxidizing power to degrade organic dye molecules. The UV irradiation can also perform photolysis in the presence of a hydrogen peroxide initiator within the catalyst system. The 3D-support structure of nickel foam substrate and needlelike rod structure of NiTe2 catalyst provides a high surface area. This 3D solid structure can solve the major issue of catalyst separation after treatment which is a major problem in powder catalysts. Our study demonstrates excellent photocatalytic dye-degradation efficiency within a very short treatment time, can replace other Fenton-based catalysts that produce a large amount of iron sludge, and are difficult to remove.

Construction of a novel two-dimensional AgBiO3/BiOBr step-scheme heterojunction for enhanced broad-spectrum photocatalytic performance.

Efficient S-scheme heterojunction photocatalysts were prepared through in situ growth of AgBiO3 on BiOBr. The self-assembled hierarchical structure of AgBiO3/BiOBr was formed from flower-like AgBiO3 and plate-like BiOBr. The optimized AgBiO3/BiOBr heterojunction possessed excellent visible-light photocatalytic degradation efficiency (83%) for ciprofloxacin (CIP) after 120 min, with 1.46- and 4.15-times higher activity than pure AgBiO3 and BiOBr, respectively. Furthermore, the removal ratio of multiple organic pollutants including tetracycline, Rhodamine B, Lanasol Red 5B and methyl orange was also investigated. Environmental interference experiments demonstrated that high pollutant concentrations, low photocatalyst dose and the addition of ions (SO42−, PO43−, HPO42−, H2PO4−) inhibited the photocatalytic activities. Subsequently, a simultaneous degradation experiment showed the competitive actions between CIP and RhB for radicals, decreasing the photocatalytic activity of CIP. Furthermore, trapping and electron spin resonance experiments showed that h+ and ˙O2− played a certain role in the degradation process and that ˙OH acted as assistant.

A direct Z-scheme heterojunction g-C3N4/α-Fe2O3 nanocomposite for enhanced polymer-containing oilfield sewage degradation under visible light

Photocatalysts g-C3N4/α-Fe2O3 with Z-scheme electron transfer mechanism exhibited excellent photocatalytic degradation HPAM efficiencies because the synergistically photocatalytic HPAM degradation by ˙OH and ˙O2−.

Construction of 3D flowers-like O-doped g-C3N4-[N-doped Nb2O5/C] heterostructure with direct S-scheme charge transport and highly improved visible-light-driven photocatalytic efficiency

Constructing a suitable heterojunction photocatalytic system from two photocatalytic materials is an efficient approach for designing extremely efficient photocatalysts for a broader range of environmental, medical, and energy applications. Recently, the construction of a step-scheme heterostructure system (hereafter called the S-scheme) has received widespread attention in the photocatalytic field due to its ability to achieve efficient photogenerated carrier separation and obtain strong photo-redox ability. Herein, a novel S-scheme heterojunction system consisting of 2D O-doped g-C3N4 (OCN) nanosheets and 3D N-doped Nb2O5/C (N-NBO/C) nanoflowers is constructed via ultrasonication and vigorous agitation technique followed by heat treatment for the photocatalytic degradation of Rhodamine B (RhB). Detailed characterization and decomposition behaviour of RhB showed that the fabricated material shows excellent photocatalytic efficiency and stability towards RhB photodegradation under visible-light illumination. The enhanced performance could be attributed to the following factors: fast charge transfer, highly-efficient charge separation, extended lifetime of photoinduced charge carriers, and the high redox capability of the photoinduced charges in the S-scheme system. Various trapping experiment conditions and electron paramagnetic resonance provide clear evidence of the S-scheme photogenerated charge transfer path, meanwhile, the RhB mineralization degradation pathway was also investigated using LC-MS. This study presents an approach to constructing Nb2O5-based S-scheme heterojunctions for photocatalytic applications.

In situ synthesis of TiO2/NC on cotton fibers with antibacterial properties and recyclable photocatalytic degradation of dyes.

A cotton fabric/titanium dioxide-nanocellulose (TiO2-Cot.) flexible and recyclable composite material with highly photocatalytic degradation of dyes and antibacterial properties was synthesized. During the preparation process, nano-TiO2 particles were synthesized through an in situ strategy and grown on cotton fiber, and were wrapped with cellulose nanocrystals (NC). The prepared TiO2-Cot. was characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The SEM and EDS results showed that nano-TiO2 particles were evenly distributed on the fiber surface. The prepared TiO2@Cot. has excellent photocatalytic efficiency of 95.68% for MB and 92.77% for AR under weak ultraviolet irradiation over 6 h. At the same time, it has excellent antibacterial activity against S. aureus and E. coli. The stability and reusability of the materials were also investigated.

Low-temperature designing of BiVO4 nanocubes with coexposed {0 1 0}/{1 1 0} facets for solar light photocatalytic degradation of methyl orange and diazinon

We present the low-temperature, template-free synthesis and photocatalytic activity of cubic-shaped monoclinic scheelite BiVO4 nanocrystals with coexposed {010}/{110} facets in this paper. The first-time diazinon photodegradation test over the studied samples under solar light irradiation was also carried out. The results showed that, by selecting suitable preparative parameters, the as-prepared 55-nm BiVO4 nanocubes with coexposed {010}/{110} facets were obtained at hydrothermal temperature as low as 60 °C. The optimized BiVO4 samples exhibited excellent photocatalytic efficiency for photodegradation of both methyl orange and diazinon under solar light irradiation. This photocatalytic activity enhancement of the {010}/{110}-facets coexposed monoclinic scheelite BiVO4 with respect to that of the bulk counterpart was supposed to be caused by the formation of surface heterojunctions between two adjunct facets of {010} and {110} that boost the charge transfer and separation.

Synthesis, Characterization and Enhanced Visible Light Photocatalytic Performance of ZnWO4-NPs@rGO Nanocomposites

ZnWO4 nanoparticles on reduced graphene oxide (ZnWO4-NPs@rGO) nanocomposites were synthesized using the hydrothermal method. Structural, morphological, optical, and photocatalytic studies of the ZnWO4-NPs@rGO nanocomposites were successfully investigated. Photo-catalytic performances of the ZnWO4-NPs@rGO nanocomposites were examined for the degradation of hazardous methylene blue dye (HMBD) in a neutral medium. ZnWO4-NPs@rGO nanocomposites show superior photo-catalytic performances over pure ZnWO4 nanoparticles. ZnWO4-NPs@rGO nanocomposites degrade ~98% dye while pure ZnWO4 nanoparticles degrade ~53% dye in 120 min. The prepared nanocomposites also show excellent recycled photo-catalytic efficiencies over multiple cycles.

Extensive solar light utilizing by ternary C-dots/Cu2O/SrTiO3: Highly enhanced photocatalytic degradation of antibiotics and inactivation of E. coli

Fabrication of a visible-light driven photocatalyst is of great vital for the elimination of antibiotics and microorganism in the wastewater and the construction of sustainable green energy systems. In this work, carbon quantum dots (C-dots) were integrated with Cu2O/SrTiO3 p-n heterojunction to optimize the photocatalytic activity. The excellent photocatalytic degradation efficiency of chlortetracycline hydrochloride (CTC·HCl) (92.6% within 90 min) and E. coli inactivation efficiency were observed over C-dots/Cu2O/SrTiO3 under visible light irradiation. It is the synergistic effect of p-n heterojunction and modification of C-dots that facilitates the separation and transfer of electron-holes. Meanwhile, the modification of C-dots improves the harvesting of long wavelength solar light of photocatalysts due to its unique up-conversion photoluminescence (UCPL) characteristics. Eventually, the possible photocatalytic degradation path of the catalyst was inferred by LC-MS spectra, and the degradation mechanism was analyzed. This study sheds light on new possibilities for the application of photocatalysts in various light sources and has broad application prospects in water treatment.

Highly efficient and reusable BiOCl photocatalyst modulating by hydrogel immobilization and oxygen vacancies engineering

• BiOCl nanosheets are immobilized by calcium alginate hydrogel through a simple crosslinking process. • BOC-CA hydrogel beads can float on the water surface. • The hydrogel beads show enhanced photocatalytic effect during the cycled ultraviolet irradiated degradation process. • The porous structure of the beads provides channels for the transport of ultraviolet induced OVs of BiOCl photocatalysts. • The hydrogel beads have excellent recovery rate and high photocatalytic efficiency over 24 degradation cycles. Photo-induced oxygen vacancies (OVs) are widely introduced as active sites in BiOCl to improve photocatalytic performance. Herein, we propose a strategy to take advantage of OVs of BiOCl nanosheets, which are immobilized in the network of water-rich calcium alginate (CA) hydrogel beads. By modulating the porous structure of the hydrogel, the OVs irradiated by UV light on the surface of BiOCl can be rapidly diffused to the deep inner of the beads, and then they disappear after the beads are immersed into the water for hours, which further enables the regeneration of even better BiOCl-CA beads. This reactive cyclic channel in a water-rich environment improves the transport of photogenerated carriers and achieves excellent cyclic photocatalytic performance. This work not only improves the recovery efficiency of photocatalytic materials but also puts forward a new system of BiOCl based hydrogel beads that can be used repeatedly in wastewater treatment.

Fiber Bragg Grating Sensing Combined with Nano-Photocatalyst for Structural Safety of Bridges and Prevention of Environmental Pollution

The photocatalytic oxidation technology of nanomaterials has the potential of treating gaseous pollutants. Therefore, the fiber Bragg grating (FBG) macro strain sensor is applied to monitor the health of the bridge. Then, a mesoporous SiO2 adsorbent is taken as the carrier to prepare SiO2@TiO2 nanocomposites with adsorptionphotocatalytic ability, which is utilized in the adsorption test of gas phase toluene pollutants. The results show that FBG macro strain sensors can effectively detect the changes in bridge T beam cracks, curvature, bending stiffness, and deflection. The difference between the deflection value calculated by the conjugate beam method and the measured value of LVDT is small. In addition, the prepared SiO2@TiO2 nanomaterials present a core–shell space structure, and have excellent toluene adsorption and photocatalytic degradation efficiency. In short, the FBG macro strain sensor can be used to monitor the progression of bridge cracks, and the SiO2@TiO2 nanomaterials can realize the enrichment and continuous degradation of gas phase pollutants.

Co-intercalation of TiO2 and LDH to reduce graphene oxide photocatalytic composite membrane for purification of dye wastewater

In this project, the Titanium dioxide nanowire (TiO2Nw) and layered double hydroxide (LDH) were introduced into the reduced graphene oxide (RGO) to make a composite material and then were assembled on the cellulose acetate (CA) membrane into photocatalytic composite membrane (RLT) through vacuum filtration with photocatalytic effect. The photocatalytic composite membrane (RLT) with high permeability and high rejection was constructed. Compared with other ratios of RLT membranes, RLT-0.5 composite membrane had a higher water flux of 432.38 L·m−2h−1bar−1, and the rejection rate of dye were above 99%. In the rejection process of 10 cycles, that the rejection rate and flux of RLT-0.5 composite membrane to methylene blue (MB), malachite green (Mg) and Congo red (CR) were more stable regardless of whether there was light or no light. Of course, the rejection effect was better under light conditions, showing its excellent photocatalytic performance. In conclusion, RLT-0.5 composite membrane had excellent water purification ability and photocatalytic efficiency, which made it have a wide application in water treatment.

Electrospun Poly(methyl methacrylate)/TiO2 Composites for Photocatalytic Water Treatment.

Electrospinning was successfully used for the one-step fabrication of poly(methyl methacrylate) (PMMA) fibers loaded with an inorganic photocatalyst—titanium oxide (TiO2). By tuning the PMMA/TiO2 ratio and the electrospinning conditions (applied voltage, needle tip-to-collector distance, and flow rates), PMMA/TiO2 composites with selected organic/inorganic ratios, tailored designs, and targeted properties were obtained. The morphology of the electrospun composites was affected by the amount of TiO2 incorporated into the PMMA fibers. In addition, the inorganic photocatalyst had an impact on the wettability, thermal stability, and optical properties of the electrospun composites. In particular, the surface wettability of the composites was strongly influenced by UV light irradiation and from hydrophobic became superhydrophilic. Moreover, PMMA/TiO2 composites had enhanced tensile strength in comparison with those of bare PMMA mats. The electrospun PMMA/TiO2 composites showed excellent photocatalytic efficiency against the model organic pollutant—methylene blue—which is very promising for the future development of membranes that are highly efficacious for photocatalytic water treatment.

Heterojunction architecture of Nb2O5/g-C3N4 for enhancing photocatalytic activity to degrade organic pollutants and deactivate bacteria in water

Water pollution has become a serious problem owing to the development of society. Photocatalysis is a promising approach to remove various pollutants in water, such as organic pollutants and antibiotic resistance bacteria. Meanwhile, the design of heterojunction between two semiconductors is an effective path to improve photocatalytic properties due to its potential in improving separation and transfer of photoinduced carriers. In this study, Nb2O5/g-C3N4 (NO/CN) composite materials were prepared through a one-step heating method. Characterizations confirmed successful preparation of NO/CN heterojunction structure and better optical properties than pure g-C3N4 and Nb2O5. NO/CN composite materials showed excellent photocatalytic efficiency for Escherichia coli (E. coli) inactivation (95%) compared with the pure Nb2O5 (10%) and g-C3N4 (77%). Meanwhile, NO/CN exhibited better organic pollutants removal (RhB for 94%, methyl orange (MO) for 15% and methylene blue (MB) for 87%) under visible light, which is likely owing to the heterojunction structure between g-C3N4 and Nb2O5 that leads to the good separation of photogenerated electron-hole pair. Free radical scavenging and electron spin resonance (ESR) experiments demonstrated that superoxide radicals (•O2−) and holes (h+) were the dominant radicals. Therefore, the NO/CN was proposed to be a promising material for effective disinfection and removal of organic contaminants in water treatment.

Development of Three-Dimensional Nickel-Cobalt Oxide Nanoflowers for Superior Photocatalytic Degradation of Food Colorant Dyes: Catalyst Properties and Reaction Kinetic Study.

In this work, we present three-dimensional flower-like nickel-cobalt oxide (F-NCO) nanosheets developed in a facile, eco-friendly hydrothermal route to apply as photocatalysts for food colorant Allura Red AC dye removal under light illumination. Using Brunauer-Emmett-Teller analysis, it was found that the F-NCO nanosheets displayed a surface area of ∼53.65 m2/g and a Barrett-Joyner-Halenda pore size of ∼14 nm, which was also confirmed by the calculated crystallite size of ∼15 nm using powder X-ray diffraction (XRD) analysis. From Williamson-Hall analysis of XRD spectra, F-NCO nanosheets revealed a crystal-lattice strain of ∼3.42 × 10-3 and a dislocation density of ∼4.397 × 1015 lines/m2 in the crystal structure. Transmission electron microscopy analysis revealed that F-NCO nanosheets accumulated to form flower-like nanostructures of <100 nm length with a d-spacing of ∼2.6 Å, which is attributed to the (311) crystallographic plane (α = γ = β = 90°, a = b = c = 8.110 Å, JCPDS No. 00-020-0781) of the cubic phase. The F-NCO nanosheets exhibited an excellent photocatalytic efficiency of ∼94.75% in ∼10 min with sodium borohydride under UV light. The Langmuir-Hinshelwood model determined pseudo-first-order reaction kinetics of dye degradation using the versus time plot. The kinetic study produced a first-order rate constant (k) of ∼0.219 min-1, resulting in ∼3.16 min half-life (t1/2) for the F-NCO-catalyzed degradation reaction. Thus outstanding photocatalytic performance of F-NCO nanosheets would display their huge potential for organic-pollutant removal from water with exceptional recyclability for wide research applications in the future.

Construction of TiO2/BiOI1−x Z-scheme heterojunction with iodine vacancy for enhancing photocatalytic oxidation of elemental mercury

The novel TiO2/BiOI1−x Z-scheme heterostructure with iodine vacancy was synthesized by calcination method and applied to photocatalytic removal of gas-phase Hg0. Combining with characterization analysis and DFT calculation results, the existence of iodine vacancy and Z-scheme generated charge-carrier migration paths in the TiO2/BiOI1−x composite were confirmed, and their effects on photocatalytic activity were further discussed. In the TiO2/BiOI1−x composite, the synergistic effect of iodine vacancy and Z-scheme heterojunction improved the migration efficiency of photogenerated charge and retain electrons and holes with high redox capacity, which effectively enhances the photocatalytic activity. The experiment results showed the TiO2/BiOI1−x composite possessed excellent photocatalytic removal efficiency of elemental mercury under influence of the synergistic effect. This study provides a new idea for designing photocatalysts with heterojunction and surface defects to purify environmental pollutants.

Universal substrate growth of Ag-modified ReS2 as visible-light-driven photocatalyst for highly efficient water disinfection

Developing highly-efficient visible-light-driven photocatalyst for water disinfection is an attractive strategy to address the current shortage of safe drinking water and environmental remediation. Since the low dependence on growth substrate and the narrow bandgap nature made ReS2 one of the best two-dimensional (2D) materials for photocatalytic sterilization. Herein, we fabricated Ag/ReS2 composite, a 0D/2D heterostructure, which can be grown on three universal substrates through a facile chemical vapor deposition (CVD) and thermal evaporation process. Benefiting from the vertical growth of ReS2 nanosheets and the hybrid effect from Ag and ReS2, the visible-light response of Ag/ReS2 can be greatly enhanced, exhibiting an excellent photocatalytic antibacterial efficiency towards Escherichia coli (E. coli) after 30 min of visible-light exposure, providing a promising environmentally friendly alternative method for water disinfection. Moreover, the universal substrate growth and good stability also endow the photocatalyst with potential applicability in various fields.

Heterometallic Mg@Fe-MIL-101/TpPa-1-COF grown on stainless steel mesh: Enhancing photo-degradation, fluorescent detection and toxicity assessment for tetracycline hydrochloride

The versatile treatment of antibiotic wastewater is a serious challenge in the practical application if an efficient, stable, and eco-friendly removal/detection method cannot be widely employed. Herein, Mg@Fe-MIL-101/TpPa-1-COF porous hybrid via covalent integration was grown on stainless steel mesh by using the solvothermal method. For the obtained hybrid, the synergistic effect of Mg and Fe optimizes the electronic structure of heterometallic Mg@Fe-MIL-101 at the atomic level, and the porous property of Mg@Fe-MIL-101 exposed more catalytically active sites and own good mass transport ability, as well as the heterojunction construction between Mg@Fe-MIL-101 and TpPa-1-COF facilitate opposite electrons migration. Moreover, the mesh-supported structure was advantageous to light-harvesting or recycling during the photo-degradation process. Based on its structure and function, the hybrid still shows excellent photocatalytic TCH degradation efficiency (94.0%, 80 min) after five cycles. Meanwhile, owing to the fluorescent property of the Mg-TC complex, the obtained hybrid can also be used as a probe for quick detection of TCH in the photocatalytic process. Furthermore, the obtained hybrid can decrease the aquatic toxicity of TCH solution, using Paramecia (protozoan) or S.aureus (gram-positive bacterium) and E.coli (gram-negative bacterium) as an ecological indicator.

Preparation of CdS@C Photocatalyst Using Phytoaccumulation Cd Recycled From Contaminated Wastewater.

Cadmium is one of the most toxic heavy metal contaminants in soils and water bodies and poses a serious threat to ecosystems and humans. However, cadmium is also an important resource widely used in many industries. The recovery of cadmium in the form of high-value products is considered as an ideal disposal strategy for Cd-contaminated environments. In this work, Pistia stratiotes was used to recycle cadmium from wastewaters through phytoaccumulation and then transformed into carbon-supported cadmium sulfide photocatalyst (CdS@C) through carbonization and hydrothermal reaction. The CdS@C photocatalyst contained a mixture of cubic and hexagonal CdS with lower band gap energy (2.14 eV) and high electron-hole separation efficiency, suggesting an excellent photoresponse ability and photocatalytic efficiency. The impressive stability and photocatalytic performance of CdS@C were demonstrated in efficient photodegradation of organic pollutants. •OH and O2•- were confirmed as the major active species for organic pollutants degradation during CdS@C photocatalysis. This work provides new insights into addressing Cd contaminated water bodies and upcycling in the form of photocatalyst.

Fabrication of Bi14W2O27/Bi2WO6 photocatalyst for improved desulfurization of thiophene under simulated sunlight irradiation

In this work, novel Bi14W2O27/Bi2WO6 nanocomposite was prepared by a modified Pechini sol-gel approach. The effect of the gelling agent, chelating agent and mole ratio of chelating agent to total metals was controlled to produce ultrafine Bi14W2O27/Bi2WO6 nanoparticles. The as-prepared Bi14W2O27/Bi2WO6 nanocomposite was characterized by XRD, FESEM, FT-IR, EDS and UV–Vis analysis. The Bi14W2O27/Bi2WO6 nanostructures exhibited excellent photocatalytic desulfurization of thiophene (~90%) after 120 min of simulated sunlight irradiation. The high-efficiency photocatalytic desulfurization of the as-prepared Bi14W2O27/Bi2WO6 can be attributed to the improved visible-light absorption, ultrafine nanoparticles, and high separation and low recombination rates of charge carriers. In addition, a reliable photocatalytic desulfurization mechanism was explained using radical trapping experiment, which indicated that the photogenerated •O2− and •OH species had a significant contribution in the photocatalytic desulfurization reactions of Bi14W2O27/Bi2WO6 nanocomposite. The excellent photocatalytic desulfurization efficiency, good recyclability, solar-driven, and simple synthesis of Bi14W2O27/Bi2WO6 nanocomposite are promising for photocatalytic applications.

Synthesis of an ultrathin MnO2 nanosheet-coated Bi2WO6 nanosheet as a heterojunction photocatalyst with enhanced photocatalytic activity

A MnO2/Bi2WO6 heterojunction photocatalyst was synthesized by simple hydrothermal method and characterized systematically. The results showed that ultrathin MnO2 nanosheets are evenly attached on the surface of Bi2WO6 nanosheets to form interfaces between MnO2 and Bi2WO6 and retains 3D flower-like structure of Bi2WO6. The MnO2 addition to Bi2WO6 increases the specific surface area, widens the light absorption region, and changes the electronic properties of Bi and W. Moreover, the defective Mn3+ increases oxygen vacancies and plays a rapid charge transfer role. A good energy band structure is formed in MnO2/Bi2WO6 to facilitate the photogenerated carrier separation. The photocatalytic studies suggest that MnO2/Bi2WO6 shows excellent photocatalytic efficiency and stability for the degradation of NO under light irradiation and inhibition for NO2 generation. MnO2/Bi2WO6 photocatalyst can produce more •OH and •O2− radicals than Bi2WO6, and the electron transfer among Mn ions enhances the removal of NO.