Nanostructured Photocatalysts Research Articles

Formation of C2 and C3 hydrocarbons through photocatalytic CO2 conversion on vertical Bi2WO6 nanosheets

In contrast to conventional nanostructured photocatalysts that only catalyze the conversion of CO2 into C1 compounds of CO and CH3OH, in this study, the Bi2WO6 nanosheets are deliberately grown to form a unique vertical configuration for achieving superior photocatalytic CO2 conversion in the production of additional C2/C3 hydrocarbons, such as HCOOCH3, CH3CHO, and CH3COCH3. These products can serve as high-caloric-value fuels and chemical feedstocks, contributing to sustainability by potentially replacing fossil fuels. The vertical Bi2WO6 nanosheets predominantly expose (010) crystal planes to the CO2 atmosphere. By modifying the nanosheet to display a jagged porous feature that exposes a higher proportion of edge surfaces perpendicular to the main exposure faces, the resulting vertical porous Bi2WO6 nanosheets catalyze the formation of additional hydrocarbons, including CH4 and CH3CH2CHO. This enhancement further strengthens the sustainability merit of this photocatalytic process. To support these experimental findings, density functional theory calculations verify the enhanced photocatalytic activity of a characteristic edge face, the Bi2WO6 (100) plane, compared to the Bi2WO6 (010) plane in the conversion of CO2 and H2O into hydrocarbons requiring multielectron transfer. This study highlights the effectiveness of the vertical Bi2WO6 nanosheets, primarily featuring exposed (010) crystal planes along with additional exposed edge faces, in promoting sustainable CO2 conversion reactions for the production of C2/C3 hydrocarbons involving multielectron transfer processes.

Cerium doped ZnO nanostructured photocatalyst for the degradation of multiple dyes

The development of cost-effective water-treatment methods to remove toxic industrial contaminants is of burgeoning demand today. This paper discusses the superior performance of Ce doped ZnO for the photocatalytic degradation of toxic cationic and anionic dyes. The excellent degradation ability of this easily manoeuvrable solid photocatalyst developed by the facile and low-cost electrochemical method, for the simultaneous removal of multiple dyes, avoiding the need for any post treatments is successfully demonstrated with the synthetic dyes methylene blue, methyl orange, congo red and their mixture. The pH dependence of the photocatalytic efficiency is correlated with its zeta potential. The improved photocatalytic efficiency is attributed to the Ce4+↔Ce3+ redox couple acting as trap centers enhancing the production of superoxide radicals and the reduction of carrier recombination. The scavenger and cyclic stability tests confirm respectively the dominant role of superoxide radicals in photocatalysis and the reusability of the photocatalyst. The photocatalyst is characterized in detail by X-ray diffraction, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, Rutherford backscattering, high-resolution transmission electron microscopy, selected area electron diffraction, surface charge analysis and diffuse reflectance spectroscopy. The study highlights the prospect of Ce doped ZnO nanostructured film as a high-performing photocatalyst for water treatment.

High-entropy alloy-enhanced ZnCdS nanostructure photocatalysts for hydrogen production

High-entropy alloys (HEA) have been shown to be potential cocatalysts for photocatalysis, but the design of ideal semiconductor/HEA composite photocatalysts is challenging due to the complexity of their composition and the interactions within multi-element systems. To address this issue, PtCuFeNiCo HEA was selected as a cocatalyst, and a ZnCdS/PtCuFeNiCo (abbreviated as ZnCdS/HEA) nanostructured photocatalyst was designed for hydrogen production from water splitting. ZnCdS/HEA was prepared using a simple liquid-phase precipitation method, a template-assisted cation exchange method, and an ultrasound-assisted recombination method. Photocatalytic experiments showed that the hydrogen production activity of ZnCdS/HEA under visible light was 5.99 mmol·g−1·h−1, which is 11.7 times that of ZnCdS and significantly higher than that of ZnCdS/Pt. Experiments and density functional theory calculations indicated that ZnCdS/HEA formed a Schottky heterojunction. The performance enhancement was attributed to the synergistic effect between PtCuFeNiCo HEA and ZnCdS, which enhanced light absorption, improved the separation and transfer of photogenerated electrons and holes, as well as provided abundant catalytic active sites and increased surface reaction activity. This study highlights the potential of HEAs and provides theoretical and experimental references for the rational design of efficient semiconductor/HEA composite materials.

Enhancing CO2 photoreduction efficiency with MXene-modified ZnO@Co3O4 double heterojunction

The photocatalytic reduction of CO2 into energy carriers holds significant industrial appeal, but achieving this process kinetically remains challenging due to the lack of well-designed catalysts. This study presents a novel 2D/3D nanostructured photocatalyst, developed by attaching a few-layer Ti3C2 MXene to polyethylenimine (PEI)-modified ZnO@CO3O4 nanocages, which are derived from a bimetallic zinc-cobalt ZIF. The resulting Mx-PEI-ZnO@Co3O4 catalyst achieved impressive yields of CO and CH4 at 594.37 and 42.67 μmol g−1 h−1, respectively, without the need for sacrificial agents and photosensitizers, and maintained remarkable stability across multiple cycles. These yields represent the highest performance for ZnO-based catalysts to date, with quantum efficiency at 380 nm reached up to 25.06 %. The unique S-scheme and Schottky junctions, along with enhanced CO2 adsorption and hydrogen-bond interactions facilitated by the conductive PEI within the Ti3C2/ZnO/Co3O4 double heterojunctions, effectively inhibit electron-hole recombination and significantly enhance CO2 photoreduction performance. This study underscores the combined benefits of double heterojunction engineering, PEI-functionalized CO2 uptake, and MXene co-catalyst integration within a single system, proposing a new approach for designing highly efficient photocatalysts for solar-driven CO2 reduction in energy-efficient fuel production.

Activation of persulfate over double S-scheme photocatalyst fabricated by decoration of Fe2(MoO4)3 and MoO3 on modified g-C3N4 for degradation of pollutants

The development of nanostructured photocatalysts with high activity is essential for the remediation of effluents. Herein, modified g-C3N4 (M-CN) was integrated with Fe2(MoO4)3/MoO3 (FMO/MO) nanoparticles by one-pot hydrothermal route, and employed to activate persulfate (PS) under visible light. The M-CN/FMO/MO nanocomposites exhibited superior performance in photocatalytic removal of three antibiotics, containing amoxicillin (AMX), azithromycin (AZT), and tetracycline (TC), and three dye pollutants, including rhodamine B (RhB), methylene blue (MB), and methyl orange (MO). The activity of M-CN/FMO/MO (20 %)/PS system for the removal of TC was 1.83, 5.86, and 55.0 folds as high as M-CN/FMO/MO (20 %), M-CN, and CN photocatalysts, respectively. The formation of a double S-scheme system enhanced the photocatalytic performance by effectively retaining electrons and holes, which have strong redox capabilities. This configuration significantly minimized charge recombination, thereby promoting efficient charge transfer and migration. Moreover, there was a significant increases in surface area compared to pure components, which provided active sites for pollutants. Eventually, the recycling test and successful growth of wheat seeds exhibited that the M-CN/FMO/MO (20 %)/PS system can be suitable for wastewater treatment. It is hoped that this system with attractive properties could be used as a promising system in wastewater detoxification.

Yolk-Shell TiO2-NRs@SiO2 with enhanced photocatalytic hydrogen production

The efficiency of photocatalysis largely hinges on the design of the photocatalysts, which can be optimized for effective light absorption, improved charge separation and transport, and faster surface reactions. In this research, we developed a yolk-shell nanostructured photocatalyst featuring one-dimensional TiO2 nanorods (NRs) cores encapsulated within a porous silica shell. After photodepositing Pt nanoparticles (NPs) onto the TiO2-NRs, the photocatalyst exhibited excellent performance. Under simulated sunlight, Pt2-TiO2-NRs@SiO2 achieved a photocatalytic efficiency of 55.47 mmol g-1h−1 using methanol as the sacrificial agent and an apparent quantum efficiency (AQE) of 7.93 % at 350 nm, surpassing most previously reported TiO2-based catalysts. This superior activity is attributed to 1D NRs, along with the hollow structure that enhances light utilization through multiple scattering. The stability and high catalytic performance of these yolk-shell structures highlight the effectiveness of our design strategy in fabricating novel, highly active, and stable catalysts.

Designing 1-nm-Thick MOF Nanosheets with Donor-Acceptor Complexes for Photosynthesis of H2O2 Using Water and Dioxygen Only.

Artificial photosynthesis of hydrogen peroxide (H2O2) presents a promising environmentally friendly alternative to the industrial anthraquinone process. This work designed ultrathin metal-organic framework (MOF) nanosheets on which porphyrin ligand as an electron donor (D) and anthraquinone (AQ) as an electron acceptor (A) are integrated as the D-A complexes. The porphyrin component allows the MOF nanosheets to absorb full-spectrum solar light while the acceptor AQ motif promotes central aluminum ion coordination, hindering layer stacking to achieve a thickness of 1.0 nm. The ultrathin D-A design facilitates the separation of electrons from the MOF skeleton to the AQ motif, which induces the direct two-electron oxygen reduction reaction (ORR) mediated by the reversible redox couple of AQ-AQH2 and multielectron water oxidation reaction (WOR) driven by holes remaining on the porphyrin part. In O2-saturated water, the ultrathin MOF nanosheets outperformed the AQ-free bulk and multilayered counterparts by 2.9 and 2.6 times in H2O2 production, respectively, achieving the apparent quantum yield of 4.8% at 420 nm. It also surpasses other benchmark photocatalysts, including the typical MOF photocatalyst, MIL-125-NH2, and organic polymeric photocatalysts. The ultrathin D-A MOF photocatalyst generated H2O2 via both two-electron ORR as a major path and two-electron WOR as a minor path. This approach presents a promising strategy for the rational design of efficient nanostructured photocatalysts for solar fuels and chemicals.

High-strength TiO2/TPU composite fiber based textiles for organic pollutant removal

Effective integration of nanostructured photocatalysts into polymer matrices is crucial for the broad practical application of fiber-based photocatalytic composite textiles. Herein, highly durable TiO2/TPU composite fibers with high TiO2 content (>30 wt. %) were prepared through wet spinning using 1D electrospun TiO2 nanofibers (TNFs). Due to the fiber reinforcement principle, the TNF/TPU composite fibers exhibited superior mechanical properties compared with pure TPU fibers. Furthermore, the TNF/TPU composite fibers with a ratio of 1:2 process impressive degradation efficiency for rhodamine B (RhB). The orientation of 1D TNFs and stronger interface between TNF and TPU matrices not only enable the excellent load sharing and transfer effects following fiber pullout and crack bridging mechanisms, but also improve photogenerated charge transfer efficiency, resulting in high strength and high photocatalytic activity. In addition, enhanced TNF exposure on the fiber is due to the hollow and porous structures of composite fibers, which is advantageous for photocatalytic degradation. Notably, when the RhB concentration exceeded 15 ppm, the TNF/TPU composite fibers exhibited higher degradation efficiency than the TNF powder. Therefore, TNF/TPU composite fiber–based textiles with high photocatalytic activity and strength are promising for overcoming the separation and recovery issues of nanostructured catalysts in practical wastewater treatment applications.

Hydrogen generation by water splitting of formic acid assisted supramolecular self-assembled g-C3N4 nanostructures

The photocatalytic hydrolysis reaction primarily unfolds on the material's surface, making the material's morphology and microstructure critical for the catalytic efficiency of photocatalysts. In this paper, a formic acid-assisted melamine hydrothermal self-assembly method is explored to prepare g-C3N4 photocatalysts with a unique morphology. The impact of sintering temperature on the morphology of the g-C3N4 photocatalysts are explored and the effect of formic acid concentration on the XRD and FTIR was analyzed. Findings reveal that the g-C3N4 nanostructures photocatalyst possesses fibrous tubular and nanosheet structures, boasting a heightened specific surface area (32.9 m2/g) and a more refined graphite-like crystalline framework. When synthesized with a 0.15 M concentration of formic acid, the g- C3N4 nanostructured photocatalyst achieved a hydrogen production rate (1289.4 μmol h−1 g−1), which is approximately 4.8 times greater than that of bulk g-C3N4 (264.7 μmol h−1 g−1). This work provides a simple method for preparing high-performance g-C3N4 based photocatalysts for visible light hydrolysis hydrogen production.

Fabrication of nanostructured AgCl-coated Ag2SO4 photocatalysts for efficient antibiotic degradation

Binary AgCl-coated Ag2SO4 nanostructures were fabricated via a facile chemical deposition method and evaluated by the visible-light photodegradation of highly toxic antibiotic tetracycline. The experimental results revealed that AgCl was successfully deposited onto the surface of Ag2SO4 particles, and the as-prepared Ag2SO4@AgCl composites exhibited significantly improved photocatalytic activity under visible light in comparison with Ag2SO4 and AgCl nanoparticles. Notably, the obtained Ag2SO4@AgCl-31 composite emerged as the most effective photocatalyst, achieved a maximum rate constant of 0.08215 min−1 under visible light, which was 3.22 times of Ag2SO4 and 2.42 times that of AgCl, respectively. Furthermore, the as-prepared Ag2SO4@AgCl-31 sample also demonstrated a good photocatalytic stability. The enhanced photocatalytic degradation performance for the Ag2SO4@AgCl composites could be primarily attributed to the formation of the core–shell heterostructures for improved charge separation.

Photocatalytic performance of (Zn,Me)–SnO2 nanoparticles (Me= Nb5+ or W6+) under UV light for efficiently degradation of organic dye pollutants

In this study (Zn,Nb)-doped SnO2 and (Zn,W)-doped SnO2 were synthetized using chemical route by calcination at 600 °C/2 h and milling at 500 rpm/1 h to verify its behavior as a photocatalyst. The powders showed high surface area: 57.1 m2/g for (Zn,Nb)-doped SnO2 and 74.3 m2/g for (Zn,W)-doped SnO2, both showed 10–25 nm of average diameter and rutile crystalline phase after morphological and structural characterizations. UV–vis spectroscopy indicated a band gap of 3.53 eV for (Zn,Nb)–SnO2 and 3.35 for (Zn,W)–SnO2. The photocatalytic activity was verified through the decomposition of Rodhamine B (RhB) aqueous solution under ultraviolet light radiation of 9W. After 120 min the efficiency of (Zn,Nb)–SnO2 was 68.5 % and for (Zn,W)–SnO2 was 71.1 %. Using a UV-lamp of 11W the efficiency in photodiscoloration of RhB aqueous solution increased to 83.2 % with (Zn,W)-doped SnO2 powder in a shorter irradiation time (90 min), indicating its potential use as nanostructured photocatalyst ceramic powder.

In situ nitrogen-doped graphene-TiO2 nano-hybrid as an efficient photocatalyst for pollutant degradation.

To solve environmental-related issues (wastewater remediation, energy conservation and air purification) caused by rapid urbanization and industrialization, synthesis of novel and modified nanostructured photocatalyst has received increasing attention in recent years. We herein report the facile synthesis of in situ nitrogen-doped chemically anchored TiO2 with graphene through sol-gel method. The structural analysis using X-ray diffraction showed that the crystalline nitrogen-doped graphene-titanium dioxide (N-GT) nanocomposite is mainly composed of anatase with minor brookite phase. Raman spectroscopy revealed the graphene characteristic band presence at low intensity level in addition to the main bands of anatase TiO2. X-ray photoelectron spectroscopy analysis disclosed the chemical bonding of TiO2 with graphene via Ti-O-C linkage, also the substitution of nitrogen dopant in both TiO2 lattice and into the skeleton of graphene nanoflakes. UV-Vis absorption spectroscopy analysis established that the modified material can efficiently absorb the longer wavelength range photons due to its narrowed band gap. The N0.06-GT material showed the highest degradation efficiency over methylene blue (MB, ∼98%) under UV and sulfamethoxazole (SMX, ∼ 90.0%) under visible light irradiation. The increased activity of the composite is credited to the synergistic effect of high surface area via greater adsorption capacity, narrowed band gap via increased photon absorption, and reduced e-/h+ recombination via good electron acceptability of graphene nanoflakes and defect sites (Ti3+ and oxygen vacancy(Vo)). The ROS experiments further depict that primarily hydroxyl radicals (OH•) and superoxide anions (O2•-) are responsible for the pollutant degradation in the process redox reactions. In summary, our findings specify new insight into the fabrication of this new material whose efficiency can be further tested in applications like H2 production, CO2 conversion to value-added products, and in energy conservation and storage.

One-pot anchoring BaBi2O6/Bi2O3 nanoparticles on oxygen vacancy rich TiO2: Double Z-scheme nanocomposites with QDs size for elimination of wastewater pollutants

The emergence of nanostructured photocatalysts with high activity offers facile solutions for removing water pollutants. In this study, a novel double Z-scheme TiO2-x/BaBi2O6/Bi2O3 nanocomposite with QDs size of about 5.52 nm was prepared by a facile one-pot hydrothermal procedure, and its activity was studied in the photocatalytic degradation of pharmaceutical and dye pollutants. The optimized nanocomposite showed a significant efficiency in the removal of tetracycline, rhodamine B, fuchsine, methylene blue, and chromium (IV), which was 12.4, 7.38, 11.1, 10.2, and 12.1 times higher than pure TiO2-x, respectively. The presence of oxygen deficiency in the crystal lattice of TiO2-x/BaBi2O6/Bi2O3 nanocomposite played a significant role in the effectual separation of photoexcited charges, increasing reactive active sites, and capturing charge carriers. Besides, providing a short distance for the rapid migration of charges to the surface of the nanocomposite was possible with the quantum size of the catalyst particles. Enforced by the established double Z-scheme heterojunctions, the charge segregation was considerably enhanced along with maintaining their redox capability. Finally, biocompatibility tests showed the harmlessness of the treated solution for agricultural use.

Tailoring the physical, optical, and structural properties of bismuth oxide to enhance its anionic, cationic, and phenol dye degradation activities

We provide a novel investigation that demonstrates the synthesis of silver-doped bismuth oxide (ABO), holmium-doped bismuth oxide (HBO), nanostructured bismuth oxide (BO), and silver-holmium co-doped bismuth oxide (CDBO) by a cost-effective and straightforward surfactant-assisted co-precipitation technique. In comparison to the BO, ABO, and HBO samples, the optical tests revealed that the CDBO sample exhibited superior photocatalytic characteristics. This is possibly attributed to the physical, optical, and structural properties of the material tailored by the synergistic effect of the adopted strategies, i.e., nanotechnology, oxygen vacancies, and co-doping. The microstructures, physicochemical properties, morphological characteristics, and compositional attributes of the synthesized materials were investigated using sophisticated characterization techniques. The intrinsic conductivity of the bismuth oxide was enhanced with the incorporation of Ag and Ho as co-dopants, as shown by the results obtained from two probe current-voltage experiments. The co-doped sample exhibited the highest efficacy in decomposing rhodamine B dye, with a degradation rate of 91 % during a mere 70-min exposure to W-lamp illumination. The most ideal settings for CDBO photocatalytic activities were identified by comprehensive parameter optimization research. These parameters include a basic pH, a catalyst dosage of 25 mg, a dye concentration of 15 ppm, and an operating temperature of 30 °C. The co-doped and nanostructured photocatalyst also showed an outstanding capability to break down orange II and phenol dye. The trapping experiments' results indicate that the hydroxyl and superoxide radicals play a significant role in the mineralization of the tested dye.

Metal–Organic Framework‐Based Hetero‐Phase Nanostructure Photocatalysts with Molecular‐Scale Tunable Energy Levels

AbstractAs an effective method to modulate the physicochemical properties of materials, crystal phase engineering, especially hetero‐phase, plays an important role in developing high‐performance photocatalysts. However, it is still a huge challenge but significant to construct porous hetero‐phase nanostructures with adjustable band structures. As a kind of unique porous crystalline materials, metal–organic frameworks (MOFs) might be the appropriate candidate, but the MOF‐based hetero‐phase is rarely reported. Herein, we developed a secondary building unit (SBU) regulating strategy to prepare two crystal phases of Ti‐MOFs constructed by titanium and 1,4‐dicarboxybenzene, i.e., COK and MIL‐125. Besides, COK/MIL‐125 hetero‐phase was further constructed. In the photocatalytic hydrogen evolution reaction, COK/MIL‐125 possessed the highest H2 yield compared to COK and MIL‐125, ascribing to the Z‐Scheme homojunction at hetero‐phase interface. Furthermore, by decorating with amino groups (i.e., NH2‐COK/NH2‐MIL‐125), the light absorbing capacity was broadened to visible‐light region, and the visible‐light‐driven H2 yield was greatly improved. Briefly, the MOF‐based hetero‐phase possesses periodic channel structures and molecularly adjustable band structures, which is scarce in traditional organic or inorganic materials. As a proof of concept, our work not only highlights the development of MOF‐based hetero‐phase nanostructures, but also paves a novel avenue for designing high‐performance photocatalysts.

Metal-Organic Framework-Based Hetero-Phase Nanostructure Photocatalysts with Molecular-Scale Tunable Energy Levels.

As an effective method to modulate the physicochemical properties of materials, crystal phase engineering, especially hetero-phase, plays an important role in developing high-performance photocatalysts. However, it is still a huge challenge but significant to construct porous hetero-phase nanostructures with adjustable band structures. As a kind of unique porous crystalline materials, metal-organic frameworks (MOFs) might be the appropriate candidate, but the MOF-based hetero-phase is rarely reported. Herein, we developed a secondary building unit (SBU) regulating strategy to prepare two crystal phases of Ti-MOFs constructed by titanium and 1,4-dicarboxybenzene, i.e., COK and MIL-125. Besides, COK/MIL-125 hetero-phase was further constructed. In the photocatalytic hydrogen evolution reaction, COK/MIL-125 possessed the highest H2 yield compared to COK and MIL-125, ascribing to the Z-Scheme homojunction at hetero-phase interface. Furthermore, by decorating with amino groups (i.e., NH2-COK/NH2-MIL-125), the light absorbing capacity was broadened to visible-light region, and the visible-light-driven H2 yield was greatly improved. Briefly, the MOF-based hetero-phase possesses periodic channel structures and molecularly adjustable band structures, which is scarce in traditional organic or inorganic materials. As a proof of concept, our work not only highlights the development of MOF-based hetero-phase nanostructures, but also paves a novel avenue for designing high-performance photocatalysts.

Synergistic effects of La-doping on ZnO nanostructured photocatalysts for enhanced MB dye degradation

In this work, we present the design and characterization of pristine and La-doped ZnO photocatalysts, prepared via a facile co-precipitation technique. A comprehensive range of characterization techniques was employed to analyze the physicochemical properties of these synthesized nanostructured photocatalysts. The slight shift in the position of peaks in the X-ray diffraction (XRD) pattern confirms successful doping (La3+) of ZnO. Additionally, the identified wurtzite phase further validates the presence of ZnO nanostructures. Subsequent photocatalytic investigations were conducted using model solutions of water and methylene blue (MB) dyes under solar irradiation, meticulously comparing the performance of pure ZnO with La3+ doped ZnO. Over the time span of 90 min, the 5 % La-doped ZnO photocatalysts exhibited an impressive 98 % degradation efficiency for MB dye, surpassing the performance of the pristine ZnO counterpart (0 % La), which achieved only 51 % degradation. This emphasizes the pronounced enhancement resulting from the incorporation of La ions. The photoluminescence (PL) spectra insights with 5 % La3+doping exhibit significant quenching, caused by the suppression of charge carrier recombination, which enhances the photocatalyst's charge transport. X-ray photoelectron spectroscopy (XPS) spectra provided crucial insights into the elemental composition and chemical states of the 5 % La3+ doped ZnO nanostructures. Through systematic reusability assessments, it was established that the 5 % La-doped ZnO photocatalysts maintain their efficiency for up to four cycles, without displaying a significant reduction in removal efficacy. This emphasizes the inherent reliability and robustness of the developed photocatalysts.

Recent Developments of Nanostructured Photocatalysts Based on Semiconducting Chalcogenides for Organic Reactions

Abstract:: The earth-abundant metal chalcogenide is a highly versatile semiconductor with unique electronic and optical properties that seem to outperform the photocatalytic properties of metal oxides and metal nanoparticles. For ages, researchers are reaping the benefits of its photocatalytic properties in numerous reactions. However, the high charge recombination rates, poor compositional stability, and a smaller number of catalytically active sites restrict its application. The development of different kinds of heterojunctions by the combination of metal-chalcogenides with other conducting and semiconducting materials like metal oxides, metal nanoparticles, g-C3N4, single-atom catalysts, and MOF results in superior photocatalytic activity. This review provides insight into the various classes of metal-chalcogenide-based heterostructures and their application in various organic transformations. A brief overview of the synergistic properties arising from the development of such heterostructures helps to understand the surface interactions so that highly stable, efficient, and selective metal-chalcogenide-based heterostructures can be developed for industrially important photocatalytic organic transformations. This review also describes the role of mediators in boosting the stability and catalytic efficiency of the metal chalcogenides. Moreover, a thorough emphasis on the morphological impact of photocatalysts in various reactions will help with the development of metal chalcogenide heterostructures with tunable morphology and bandgap.

TiO2-MoS2-PMMA Nanocomposites for an Efficient Water Remediation.

An improvement of water supply and sanitation and better management of water resources, especially in terms of water reuse, is one of the priorities of the European Green Deal. In this context, it is crucial to find new strategies to recycle wastewater efficiently in a low-cost and eco-friendly manner. The immobilization of inorganic nanomaterials on polymeric matrices has been drawing a lot of attention in recent years due to the extraordinary properties characterizing the as-obtained nanocomposites. The hybrid materials, indeed, combine the properties of the polymers, such as flexibility, low cost, mechanical stability, high durability, and ease of availability, with the properties of the inorganic counterpart. In particular, if the inorganic fillers are nanostructured photocatalysts, the materials will be able to utilize the energy delivered by light to catalyze chemical reactions for efficient wastewater treatment. Additionally, with the anchoring of the nanomaterials to the polymers, the dispersion of the nanomaterials in the environment is prevented, thus overcoming one of the main limits that impede the application of nanostructured photocatalysts on a large scale. In this work, we will present nanocomposites made of polymers, i.e., polymethyl methacrylate (PMMA), and photocatalytic semiconductors, i.e., TiO2 nanoparticles (Evonik). MoS2 nanoflakes were also added as co-catalysts to improve the photocatalytic performance of the TiO2. The hybrid materials were prepared using the sonication and solution casting method. The nanocomposites were deeply characterized, and their remarkable photocatalytic abilities were evaluated by the degradation of two common water pollutants: methyl orange and diclofenac. The relevance of the obtained results will be discussed, opening the route for the application of these materials in photocatalysis and especially for novel wastewater remediation.

Intensification of organic pollutant degradation under visible light irradiation using ZnO nanostructured photocatalysts doped with praseodymium

Zinc oxide nanostructures doped with praseodymium (ZnO:Pr) at varying Pr content (0.05 % to 1.0 % w/w) were synthesized using the electrospinning-calcination technique. Comprehensive morphological and structural characterizations were conducted through SEM, XRD, and XPS analyses. In addition, diffuse reflectance and photoluminescence spectroscopy measurements were performed to assess the optical properties of materials. The produced photocatalysts (ZnO:Pr) were then employed for the degradation of methylene blue dye and oxytetracycline under visible-light irradiation. ZnO:Pr(0.1 %) demonstrated the best photocatalytic performance against methylene blue showing a pseudo-first-order rate constant of k = 3.630 × 10-2 min−1. Investigation of oxytetracycline photodegradation with ZnO:Pr(0.1 %) revealed a pseudo-second-order rate constant of ks = 1.165 × 10-1 L mg−1 min−1, resulting in a reaction half-life (τ½) of approximately 1 min under optimal conditions. Total organic carbon and mass spectrometry analyses highlighted mineralization and identified the main reaction intermediates, respectively, for the oxytetracycline photodegradation. The photodegradation mechanism of oxytetracycline was proposed by the photocatalytic degradation measurements in the presence of scavengers such as hydroquinone and isopropanol. These nanostructures exhibited robust photocatalytic activity over multiple cycles, demonstrating excellent stability. This study underlines the promising potential of ZnO:Pr(0.1 %) as an efficient photocatalyst able to intensify the photodegradation of organic pollutants.