Photocatalyst Powders Research Articles

Uniformly assembled polypyrrole-covered bacterial cellulose/g-C3N4 flexible nanofiber membrane for catalytic degradation of tetracycline hydrochloride

As an emerging and promising technology, photocatalytic technology can effectively remove trace organic pollutants such as tetracycline hydrochloride (TC-H, an antibiotic) in water. However, the research on photocatalysis is mainly focused on the powder photocatalyst, which is difficult to separate from the water body after use. Generally, fixing the photocatalytic material on a specific carrier can effectively avoid the above problems. In this article, we uniformly assembled g-C3N4 on bacterial cellulose (BC) with 3D nanofiber network and enhance its catalytic activity by polypyrrole (PPy). Different from the modification of the photocatalyst in most studies, we have effectively improved the catalytic activity through the design of the support material and reactor in this work. The PPy@(BC/g-C3N4) flexible membrane prepared has high-efficiency catalytic performance (64.28%, 2 h, TC-H) under a low-power xenon lamp (λ > 420 nm) in the reactor designed, which is 5.27 times the catalytic efficiency of the original BC/g-C3N4(12.20%, 2 h, TC-H). After 10 times of repeated use, it can stably retain more than 80% of the initial catalytic activity. Specifically, we propose to introduce oxygen in the active substrate generation stage and construct a photoelectrocatalytic reaction cell. This study can be used as a general strategy to prepare flexible membrane materials with high-efficiency catalytic properties.

A Polyimide-Based Photocatalyst for Continuous Hydrogen Peroxide Production Using Air and Water under Solar Light

A Polyimide-Based Photocatalyst for Continuous Hydrogen Peroxide Production Using Air and Water under Solar Light

A novel strategy of hydrothermal in-situ grown bismuth based film on epoxy resin as recyclable photocatalyst for photodegrading antibiotics and sterilizing microorganism

Various photocatalyst powders (such as bismuth oxide/bismuth oxyiodide) can remove contaminants and microorganism from waterbody efficiently, but their practical application was limited due to poor recovery performance. To address this problem, we reported the construction of epoxy resin induced hydrothermal in-situ growth Z-scheme bismuth oxide/bismuth oxyiodide heterostructure film on various metals as a recycled photocatalysts. Novel epoxy resin was proposed to substitute in-situ growth film of seed layer constructed by magnetron sputtering and electrodeposition between film and metals. The universal flower-like microspheres (diameter: 3–5 μm) bismuth oxide/bismuth oxyiodide films (thickness: 13 μm) were grown on various metals. Additional film decorated by photothermal catalyst nanoparticles (such as Ag, diameter: 200 nm) was constructed. The metal/epoxy resin/film can efficiently photodegrade 83.8% of Rhodamine B (RhB) and 73.2% of triclosan (TCS) within 210 min under the visible light illumination. Furthermore, antimicrobial efficiency of bismuth oxide/bismuth oxyiodide neglected in the reported study was assessed and exhibited inactivation of >99.99% Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) at 6 h and 9 h of irradiation. The Z-scheme heterostructure film can simultaneously produce O2− and OH. In addition, there was a synergistic effect between the film and the silver nanoparticles, silver nanoparticles can not only further enhance the separation efficiency of photocarriers and generation efficiency of free radical, but also form silver ions to further improve the antimicrobial property. Therefore, metal/epoxy resin/film had broad application prospects as an easily recycled photocatalyst and can also be adopted to prepare other films for photocatalytic application.

The floating photocatalytic spheres loaded with weak light-driven TiO2-based catalysts for photodegrading tetracycline in seawater

To effectively treat organic pollutants in seawater, this study fabricated different floating photocatalytic spheres by loading TiO2-based photocatalysts to degrade tetracycline in simulated seawater. In photodegradation for tetracycline, the content of the active TiO2 component in the powder photocatalyst played a major role in degrading the performance of the material. A polyurethane porous sponge with a large specific surface area was used as a carrier in loading the powder photocatalyst to avoid the interference of salt ions in seawater for photodegradation. The adsorption ability and performance in tetracycline photodegradation of the PU sponge-filled photocatalytic spheres were significantly higher than those of PMMA photocatalytic spheres under the same conditions. The Pt-deposited P25-A (Pt–P25-A) powder photocatalyst with the strongest visible light response exhibited the highest performance. The rate removal for tetracycline in the simulated seawater by the PU sponge-filled spheres loaded with Pt–P25-A exceeded 80% after 20 h.

Self-Assembled Nanocomposites and Nanostructures for Environmental and Energy Applications

Self-assembled nanocomposites are attracting considerable attention owing to their controllable architectures and self-assembly processes, as well as the increase in worldwide environmental effects and energy needs. Further understanding of the self-assembly procedure for improving environmental and energy applications would advance the design and manufacture of nanomaterials for various applications. These materials can be grouped into major categories for various application fields, including powder photocatalysts, membrane photocatalysts, and thin-film thermoelectric nanomaterials. These self-assembled nanomaterials can be used for environmental and energy applications, such as wastewater purification, hydrogen production by water splitting, energy storage, and energy harvesting. In this review, a brief introduction to the definitions and classifications of self-assembled nanocomposites is provided. We aim to provide a summary of the recent research related to self-assembled nanocomposites and nanostructures used for environmental and energy applications. Moreover, typical examples and discussions are aimed at demonstrating the advantages of self-assembled nanostructures. At the end of each section, the structural properties and the application of the nanocomposite or nanostructure are summarized. Finally, we provide perspectives for future research on the design and fabrication of self-assembled nanocomposites and nanostructures.

ZIF-8-derived photocatalyst membrane for water decontamination: From static adsorption-degradation to dynamic flow removal

Photocatalysis has been considered a promising method for environmental purification. However, powder nanomaterials are not suitable for large-scale application due to the limit of low recyclability and energy-intensive operation. Integrating and depositing powder photocatalysts on monolithic substrates may solve these issues. In this study, a ZIF-8 photocatalyst membrane and its derived product (ZnS photocatalyst membrane) was constructed by a facile in-situ treatment of cellulose-based substrate (take filter paper as an example). Both the two nanomaterials were confirmed to be tightly anchored to filter paper with the aid of chemical interaction. Under visible light irradiation, excellent dynamic-flow photocatalytic removal efficiencies of methylene blue (MB) degradation (97% within 80 min, k = 0.042 ± 0.002 min−1) and Cr(VI) reduction (100% within 60 min, k = 0.116 ± 0.007 min−1) were achieved by the prepared ZIF-8 photocatalyst membrane and its derived ZnS photocatalyst, respectively. Considering the high MB adsorption capacity and facile regeneration process of ZIF-8 photocatalyst membrane, the adsorption-degradation strategy was promising for its universal applications. The MB degradation pathway and photocatalytic mechanisms were also explored. Ultimately, a comprehensive discussion on the advantages and implications of prepared photocatalyst membranes for photocatalytic water treatment was rationally proposed. This study provided a promising method for water decontamination and demonstrated the significant superiority of monolithic membrane for photocatalytic water treatment.

Solar energy for liquid wastewater treatment with novel TiO2 supported catalysts

Photocatalytic oxidation is promising technology for removal of recalcitrant pollutants from water. Solar energy can be an interesting radiation source since the operating costs can be lower. However, the use of powder photocatalyst is a major drawback of the technology since suitable separation technologies are required and catalysts recovery is difficult. This work aims to test the suitability of using polymeric supports to immobilize TiO 2 in the reactor and apply it for parabens removal from water by solar photocatalytic oxidation. Polyurethanes (PU) and polydimethylsiloxane (PDMS) membranes were prepared and modified with TiO 2. While PU materials are only able to adsorb (35% in 1 h) parabens whichever the modification applied, modified PDMS was able to promote parabens photocatalytic oxidation removing 20% in 1 h under solar energy. Plasma/UV modification was able to active PDMS membranes (16% of methyl paraben (MP) removal) and further entrapment of TiO 2 in the polymeric matrix did not improve the process (18% of MP removal). Thus, only the superficial TiO 2 was active. Results show that PDMS is suitable material to support TiO 2 aiming photocatalytic wastewater treatment process using the Sun as a clean and renewable energy source.

Polystyrene-NiO-CNT composite ball and film for photocatalytic degradation of methylene blue dye

Immobilization of photocatalysts on the solid support is important for environmental pollutant removal. We have prepared NiO-CNT composite photocatalyst following co-precipitation and catalytic pyrolysis method. The polystyrene-NiO-CNT composite film was prepared by adding 200 mg of NiO-CNT in 10 mL chloroform and different wt% (30%, 50%, and 70%) of waste expanded polystyrene (WEPS), and subsequently, the film was cast on a petri-dish with a film thickness of 0.45 mm. The charcoal balls (weight = 2 g, diameter = 2 cm) were coated with PS-NiO-CNT (30% PS) solution. The prepared photocatalyst powder, ball, and film, were compared for degradation of 100 mL methylene blue (MB) dye (10 mg/L). It was found that the powder and ball catalyst has exponential degradation, whereas the film catalyst has linear degradation nature. The powder sample (200 mg/100 mL) can degrade ∼ 96% of MB while a ball can degrade ∼ 86%, a film with 30% PS can degrade ∼ 81% within 4 h. The film and ball are magnetic, easily recyclable, and can be reused up to the 4th cycle without an appreciable loss (<10%) of degradation efficiency.

Current Approach to Develop TiO2 Thin Film as Photocatalysts for Low-Density Plastic Degradation

Low-density plastic bags waste disposal is a big issue in the current scenario which gives rise to grave threats to human beings and environmental health also. Amid the various approaches applied for dealing with the problem, photocatalytic biodegradation in visible light irradiation is an advanced prospect that has received attention nowadays. The present review paper is to provide an outline of the current progress on the synthesis of titania (TiO2) thin-film photocatalysts for solid waste removal. The Photocatalysis method contains the photoinduced redox reactions in the photocatalyst which facilitates the degrading of almost organic compounds like polyethylene into carbon dioxide (CO2), water, and other substance. One of the most excellent photocatalysts which has grabbed attention in an application is titania because of its high photocatalytic activity and chemical stability. The synthesis of the photocatalyst as a thin film is a result of the unfeasible application of conventional powder photocatalyst which may cause a certain environmental hazard. The photocatalyst-coated thin film along with some environmental applications have also been reviewed. Likewise, various approaches for modifying thin-film property, film deposition techniques, and deposition on various substrates are used for the enhanced photocatalytic activity of the TiO2 thin film.

One-step preparation of Ag-incorporated BiVO4 thin films: plasmon-heterostructure effect in photocatalytic activity enhancement

Ag-incorporated BiVO4 thin film with high photocatalytic activity is a great candidate for industrial wastewater treatment, enhancing the photoactivity of BiVO4, as well as solving the recyclability and reusability drawback of powder photocatalysts. Therefore, a novel one-step process of the reactive magnetron sputtering technique was employed, which to this day was never utilized to synthesis Ag-incorporated BiVO4 thin films. The effect of Ag incorporation on the photocatalytic properties was comparatively investigated. The photoactive phases e.g. monoclinic BiVO4, Ag4V2O7, α-AgVO3 were detected by X-ray diffraction (XRD). Various morphologies, depending on the Ag content, were observed by field emission electron microscopy (FESEM) along with Ag nanoparticles on the film surface. X-ray photoelectron spectroscopy (XPS) proved the existence of Bi and V exclusively in their Bi+3 and V+5 oxidation states, while Ag was present in Ag+ and Ag0, which are correspondent with silver vanadates and Ag nanoparticles, respectively. The thin film with 24 at. % Ag exhibited superior photocatalytic performance with a 99 % photodegradation of Rhodamine-B at neutral pH under visible light, as a result of having the lowest bandgap (1.96 eV), proper distribution of Ag4V2O7 phase, the plasmonic effect of Ag nanoparticles on the film surface, and the lower recombination rate compared to the pristine sample demonstrated by photoluminescence (PL) spectra. The recyclability experiment ensured the high stability of the thin films after three consecutive cycles, and the role of superoxides (•O2−) and photogenerated holes were found to be crucial using scavengers. The results confirmed the synergistic enhancement of the photocatalytic activity through Ag-incorporated BiVO4 heterostructure and the plasmonic effect, as well as solving the low photoactivity of BiVO4 at neutral pH.

Prospects for creating regenerated photocatalytic materials for solar water treatment units

This article considers the possibility of obtaining regenerated photocatalytic materials of cylindrical shape for flow-through water purification systems. The method of cementation in a ceramic base matrix was compared to the method of laser fusion with a ceramic base of standard powder photocatalysts (ZnO, TiO2) according to the criteria of photocatalytic activity. The obtained materials were tested in a flow-through water purification unit (WPU) during the photo-oxidation of cationic - methylene blue (MB) and anionic - methyl orange (MO) model organic pollutants. The efficiency of water purification from MB at three cycles of regeneration of the obtained materials’ photocatalytic surface by layer-by-layer grinding was shown.

Thermo-photoactivity of pristine and modified titania photocatalysts under UV and blue light

Five commercially available TiO2 powder photocatalysts and 8 series of synthesized in laboratory TiO2-based samples, containing deposited Mn, Cu, Pt, and Ag, have been studied in test reaction of complete oxidation of gaseous VOC under UV (370 nm) and blue (440 nm) light at a temperature within a range 40–140 ℃. The dependencies of the activity on the reaction temperature are obtained, the influence of the nature and amount of the modifier on the change in activity under both types of radiation is shown. The obtained results demonstrate significant differences in the influence of the modifier’s nature on the thermal enhancement of the photocatalytic process. The data obtained show a difference between thermal intensification of photooxidation under UV and visible light and may be useful for practical implementation of photocatalytic technologies with an extended action spectrum of photocatalysts.

Solar Light Photoactive Floating Polyaniline/TiO2 Composites for Water Remediation.

In the present study, the development of innovative polyurethane-polyaniline/TiO2 modified floating materials applied in the sorption and photodegradation of rhodamine B from water matrix under solar light irradiation is reported. All the materials were fabricated with inexpensive and easy approaches and were properly characterized. The effect of the kind of polyaniline (PANI) dopant on the materials’ behavior was investigated, as well as the role of the conducting polymer in the pollutant abatement on the basis of its physico-chemical characteristics. Rhodamine B is removed by adsorption and/or photodegradation processes depending on the type of doping agent used for PANI protonation. The best materials were subjected to recycle tests in order to demonstrate their stability under the reaction conditions. The main transformation products formed during the photodegradation process were identified by ultraperformance liquid chromatography-mass spectrometry (UPLC/MS). The results demonstrated that photoactive floating PANI/TiO2 composites are useful alternatives to common powder photocatalysts for the degradation of cationic dyes.

Full solar spectrum driven CO2 conversion over S-Scheme natural mineral nanocomposite enhanced by LSPR effect

Using natural mineral to realize photocatalytic reduction of CO2 is promising but remains a great challenge. Herein MoO3-x quantum dots (QDs) immobilized on acid modified palygorskite (H-Pal) nanocomposite was prepared as powder photocatalyst for CO2 conversion. The effect of various mass fractions of MoO3-x on CO2 reduction was investigated. Results reveal that the 30% MoO3-x/H-Pal demonstrates remarkable CO2 photoreduction property with a CH3OH yield rate of about 6.2 μmol·g−1·h−1 under full spectrum irradiation. The MoO3−x QDs possess high localized surface plasmon resonance (LSPR) effect induced by oxygen vacancy (Ov) not only enables the efficient capture of NIR photons, but also build S-scheme heterostructure with H-Pal mediated by Ov enhancing the separation of charge carriers as well as preserving high redox potential. In addition Ov act as active sites promoting the adsorption and activation of CO2. This work may provide a cost-effective strategy for the practical application of artificial photosynthesis.

Deposition of Hybrid Photocatalytic Layers for Air Purification Using Commercial TiO2 Powders.

Photocatalytic nanomaterials, using only light as the source of excitation, have been developed for the breakdown of volatile organic compounds (VOCs) in air for a long time. It is a tough challenge to immobilize these powder photocatalysts and prevent their entrainment with the gas stream. Conventional methods for making stable films typically require expensive deposition equipment and only allow the deposition of very thin layers with limited photocatalytic performance. The present work presents an alternative approach, using the combination of commercially available photocatalytic nanopowders and a polymer or inorganic sol–gel-based matrix. Analysis of the photocatalytic degradation of ethanol was studied for these layers on metallic substrates, proving a difference in photocatalytic activity for different types of stable layers. The sol–gel-based layers showed an improved photocatalytic activity of the nanomaterials compared with the polymer layers. In addition, the used preparation methods require only a limited amount of photocatalyst, little equipment, and allow easy upscaling.

A Z-scheme system constructed from WO3 modified TiO2 doped with Cr and Sb for visible light-driven overall water splitting

An artificial Z-scheme system using powder photocatalysts and a reversible redox mediator for the overall water splitting has been attracting attention for producing renewable H2 using solar energy. For the efficient use of this system, the development of efficient photocatalysts utilizing longer wavelength light is essential. TiO2 doped with Cr and Sb (TiO2:Cr/Sb) is one of the visible-light-active photocatalysts which has a bandgap of ca. 2.2 eV and absorbs light up to near 600 nm. However, TiO2:Cr/Sb powder in the Fe3+/Fe2+ reversible redox mediator showed negligible activity under visible light irradiation (λ &amp;gt; 460 nm). In this work, it was found that the photocatalytic performance for O2 evolution over TiO2:Cr/Sb modified with WO3 (WO3-TiO2:Cr/Sb) using the Fe3+/Fe2+ mediator was more than 15 times higher than that without modification. The apparent quantum efficiency of WO3-TiO2:Cr/Sb was estimated to be ca. 0.8% at 510 nm. The overall water splitting activity of Z-scheme water splitting (H2/O2 = 2), in combination with Ru/SrTiO3:Rh, was 9 times improved by the WO3 modification compared to that without modification. From the results of photoelectrochemical measurements, it was surmised that the loaded WO3 on the surface of TiO2:Cr/Sb may promote both reduction of Fe3+ to Fe2+ and oxidation of H2O to O2.

Constructing porous channels in superhydrophilic polyethersulfone composite nanofibrous membranes for sustainably enhanced photocatalytic activities in wastewater remediation

Photocatalysis is regarded as one of the most promising technologies to remediate wastewater for environmental friendliness. However, most of the powder photocatalysts still suffer from poor hydrophilicity, easy aggregation and difficult recycling, which have restricted their further applications in wastewater treatment. In this study, we constructed porous and superhydrophilic composite polyethersulfone nanofibrous membranes to load titanium dioxide (TiO2) and graphitic carbon nitride (g-C3N4) photocatalysts to achieve the UV light and visible light driven photocatalytic degradation for organic contaminants, respectively. Particularly, the resultant mesopores in nanofibers could promote the diffusion of contaminant molecules, facilitate the exposure of photocatalytic active sites, improve the light absorption, and finally enhance the photocatalytic activities. Moreover, benefiting from the further removal of poly(vinylpyrrolidone) during the repetitive reuse process, it was provided with a sustainable enhancement of reusability for the composite nanofibrous membrane, which was superior to most of the traditional wastewater remediation materials. Overall, these encouraging features of porous and superhydrophilic composite nanofibrous membrane not only make it promising candidate for wastewater purification, but also offer new pathways to develop advanced nanofibrous materials for diverse catalysis, adsorption and separation applications in environment remediation.

Superhydrophilic and polyporous nanofibrous membrane with excellent photocatalytic activity and recyclability for wastewater remediation under visible light irradiation

Wastewater remediation via photocatalysis for the environmentally friendly degradation of organic contaminants has attracted increasing attention in recent years. Nevertheless, the efficiency of such a promising technology is still unsatisfactory due to the low light utilization, poor hydrophilicity, easy aggregation, and difficult recycling of powder photocatalyst materials. In this study, we developed a versatile strategy for the design of superhydrophilic and polyporous nanofibrous membrane with excellent photocatalytic activity and outstanding recyclability via the combination of loading modified photocatalyst and constructing hydrophilic channels in the electrospinning nanofibers. A novel graphitic carbon nitride photocatalyst with the simultaneous introduction of boron-doped and nitrogen-deficient structure (B-C3N4) was synthesized firstly, and then blended with polyethersulfone and Poly(vinylpyrrolidone) (PVP) to fabricate composite nanofibrous membrane via electrospinning technology. After a simple water extraction process to remove PVP, a highly Polyporous and superhydrophilic nanofibrous membrane (PBCN) was obtained. The resulting mesopores and channels existing in the nanofibers could facilitate the diffusion of contaminant molecules, expose more photocatalysis sites of B-C3N4, and finally improve the photocatalytic activity. Especially, thanks to the continuous removal of residue PVP in PBCN, it was provided with a sustaining enhancement of reusability during the repetitive reuse process, which was superior to most of the traditional wastewater remediation materials. In addition, a possible photocatalytic mechanism for degrading organic contaminants by the PBCN was proposed. In this work, we not only prepared superhydrophilic, polyporous and visible light responsive nanofibrous membrane for the photocatalytic degradation of various organic contaminants, but also introduced a novel approach towards the design of advanced nanofibrous materials for diverse catalysis, adsorption and separation applications in environment remediation.

Development of Zinc Hydroxide as an Abundant and Universal Cocatalyst for the Selective Photocatalytic Conversion of CO2 by H2O

AbstractWater splitting is always a strongly competitive reaction against the photocatalytic conversion of CO2 using H2O as the electron donor over powder photocatalysts. At present, only Ag nanoparticles function as a universal cocatalyst for the activity and selectivity of CO2 conversion in this regard. Herein, abundant Zn(OH)2 is investigated over various typical powder photocatalysts and shows attractive universality in the enhancement of activity and selectivity toward CO evolution from CO2. Taking ZnTa2O6 as an example, the rate of formation of H2 was suppressed (from 32.8 to 5.8 μmol h−1), while the formation of CO was dramatically promoted (from 18.4 to 81.4 μmol h−1) with Zn(OH)2 as the cocatalyst. Zn ions dissolved in solution and an alkaline electrical double layer of the photocatalysts are proved to be important for the function of Zn(OH)2.

Magnetic recyclable self-floating solar light-driven WO2.72/Fe3O4 nanocomposites immobilized by Janus membrane for photocatalysis of inorganic and organic pollutants

For environmental scientists, developing an efficient, stable, and recyclable solar light photocatalyst is a challenging issue. Even though powder photocatalysts have excellent photocatalytic activity, their recyclability and reusability is a noteworthy problem. Therefore, it is very crucial to develop a new photocatalysis system that possesses efficient photocatalytic activity, excellent stability, and ease of recyclability, and is free of secondary pollution. Herein, a solar light active WO2.72/Fe3O4 nanocomposite photocatalyst was immobilized in hydrophobic porous recycled triacetate cellulose (rTAC) to solve the reusability problem and was electrospun on hydrophilic nonwoven polyvinyl alcohol (PVA) to fabricate a self-floatable recyclable Janus membrane. TAC possesses very important properties such as high moisture permeability and high light transmittance, which helps all the light irradiated to be utilized by the photocatalyst and hydrophobicity, which increases the ease of floating. The recyclable Janus membrane was purposefully designed so that the contaminated water can be attracted by PVA due to its hydrophilicity and pass to porous rTAC, where the pollutant and the photocatalyst come into contact and photocatalysis takes place, while the hydrophobicity of the rTAC makes the Janus membrane float on the surface of polluted water. The photocatalytic property of the synthesized recyclable Janus membrane was studied for the photodegradation of rhodamine B (Rh B) and methylene blue (MB) as well as the photoreduction of the carcinogenic pollutant Cr(VI) under solar light irradiation. The recyclable Janus membrane presented an outstanding photocatalytic property for the photodegradation of Rh B and MB dyes and the photoreduction of Cr(VI). It also displayed excellent cyclic stability and ease of recyclability for both organic and inorganic pollutants after multiple experimental cycles. The Janus membrane also presented better photocatalytic activity than previously reported photocatalysts for MB photodegradation. Therefore, the developed interfacial photocatalysis system and the recyclable Janus membrane are promising candidates for environmental remediation under solar light irradiation. This study paves the way for the design of an environmentally friendly, effective, and stable photocatalyst for wastewater treatment.